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Gravely 260Z - Rpm's bog down when moving under load
#1
Turbodriven
Turbodriven
Hey everyone. I'm new to zero turns but very mechanical in experience (ex Navy fighter jet mechanic).
Got a used 2005 260z (Kohler CV740 Command Pro 27) for cheap that starts and idles (and throttles up and down) perfect. Sounds good sitting still. Even starts mowing like a bat out of hell for the first few seconds. But then after 20 feet of moving at speed (and even worse when blades are engaged) the motor quickly starts winding down to about 20-30% rpms (or so it feels) and barely mows. Like someone stuck a banana in the tailpipe. If I disengage blades and pull back the controls to a stop, the rpms pick back up and she idles/sounds normal again. But then the behavior returns when I push the sticks forward.
I put new plugs in it and after mowing for five minutes I pulled both plugs out and they were both dry and thick black (rich).
1. This behavior remains unchanged after installing a brand new carburetor, new fuel pump, fuel filter, spark plugs, air filter, and fresh gas.
2. Compression tests on cyl1=170psi and cyl2=175psi
3. There is no smoke in the oil dipstick (crankcase) after running and the oil level is correct.
4. Behavior does not correct when unscrewing the gas cap (*even though "lean" doesn't appear to be the issue)
5. Governor linkage was set per specs when I installed the new carb.
6. Battery is good and I hooked up my multimeter while running and it maintains 13.x+ volts throughout the whole behavior. Also, there is no spikes when engaging PTO clutch. That system appears to be operating normal??
7. I had the deck off last week and all three spindles seem to spin fine.
I'm not sure what else to think. The basic behavior is that the motor slows down under load. So either the normal load is affecting something wrong with the motor, or an abnormally heavy load is too great for the healthy motor.
Any ideas on what to check or fix to get this right?
Got a used 2005 260z (Kohler CV740 Command Pro 27) for cheap that starts and idles (and throttles up and down) perfect. Sounds good sitting still. Even starts mowing like a bat out of hell for the first few seconds. But then after 20 feet of moving at speed (and even worse when blades are engaged) the motor quickly starts winding down to about 20-30% rpms (or so it feels) and barely mows. Like someone stuck a banana in the tailpipe. If I disengage blades and pull back the controls to a stop, the rpms pick back up and she idles/sounds normal again. But then the behavior returns when I push the sticks forward.
I put new plugs in it and after mowing for five minutes I pulled both plugs out and they were both dry and thick black (rich).
1. This behavior remains unchanged after installing a brand new carburetor, new fuel pump, fuel filter, spark plugs, air filter, and fresh gas.
2. Compression tests on cyl1=170psi and cyl2=175psi
3. There is no smoke in the oil dipstick (crankcase) after running and the oil level is correct.
4. Behavior does not correct when unscrewing the gas cap (*even though "lean" doesn't appear to be the issue)
5. Governor linkage was set per specs when I installed the new carb.
6. Battery is good and I hooked up my multimeter while running and it maintains 13.x+ volts throughout the whole behavior. Also, there is no spikes when engaging PTO clutch. That system appears to be operating normal??
7. I had the deck off last week and all three spindles seem to spin fine.
I'm not sure what else to think. The basic behavior is that the motor slows down under load. So either the normal load is affecting something wrong with the motor, or an abnormally heavy load is too great for the healthy motor.
Any ideas on what to check or fix to get this right?
#2
B
bertsmobile1
B
bertsmobile1
Check both plugs are firing
The ignition is via flywheel magnetos so the timing is fixed
The coils use a hall effect trigger which is embedded into the coil
They work on the negative side of the induced voltage
Each has a common kill wire that grounds the coils
When each coil fires they send a ripple down the kill wire and to prevent this there is a set of diodes either in the coil as part of the trigger chip or in the wire itself the latter is usual Kohler practice
When these diodes fail the timing goes off so you are only running on 1 cylinder
Usual test is to remove the kill wire and see if the problem persists .
Before doing this check that the solenoid in the carb is working or there is no way to stop the engine short of pulling the plug leads off
NOW forget every thing you learned in the navy
Mowers are made down to a low ticket price not up to military reliability standards
When idling or driving on relatively flat ground the engine runs on the idle circuit alone because there is not enough load on the engine to cause the carb butterfly to open enough to activate the main jet
this is why the manual calls 3600 rpm "High Idle"
Also new does not mean good
At least 1/2 of what is sold on Amazon & Ebay is either fake , wrong or defective parts bought as scrap then sold as "fits a ..."
When going down to face book you are looking at 75 %
Kohler have reasonably good service manuals available from the Kohler web page as a free download
If you can follow navy instructions , the Kohler manual should be a doddle
Finally thank you for your years of service
The ignition is via flywheel magnetos so the timing is fixed
The coils use a hall effect trigger which is embedded into the coil
They work on the negative side of the induced voltage
Each has a common kill wire that grounds the coils
When each coil fires they send a ripple down the kill wire and to prevent this there is a set of diodes either in the coil as part of the trigger chip or in the wire itself the latter is usual Kohler practice
When these diodes fail the timing goes off so you are only running on 1 cylinder
Usual test is to remove the kill wire and see if the problem persists .
Before doing this check that the solenoid in the carb is working or there is no way to stop the engine short of pulling the plug leads off
NOW forget every thing you learned in the navy
Mowers are made down to a low ticket price not up to military reliability standards
When idling or driving on relatively flat ground the engine runs on the idle circuit alone because there is not enough load on the engine to cause the carb butterfly to open enough to activate the main jet
this is why the manual calls 3600 rpm "High Idle"
Also new does not mean good
At least 1/2 of what is sold on Amazon & Ebay is either fake , wrong or defective parts bought as scrap then sold as "fits a ..."
When going down to face book you are looking at 75 %
Kohler have reasonably good service manuals available from the Kohler web page as a free download
If you can follow navy instructions , the Kohler manual should be a doddle
Finally thank you for your years of service
#3
Turbodriven
Turbodriven
Thanks bertsmobile1. I'm reading through the Kohler CV740 book as we speak. And ironically I'm at the ignition coil section. Tomorrow I'm going to look further into that chapter and do some testing like you suggested. It sounds like low (or no) spark is a very good possibility. But then again, so did all the other things I've checked prior to this, so who knows. In the Kohler manual it has a troubleshooting guide for "low engine" power. Every one of their suggestions passes. 
Note: I've been out of the Navy for more than 3 decades. But in the last 1 decade I have rebuilt 30+ jet ski motors. And if there is one thing I know from that, it's that a motor can run great on the bench, and then crappy under load if something isn't right. This seems to be no different.
Note: I've been out of the Navy for more than 3 decades. But in the last 1 decade I have rebuilt 30+ jet ski motors. And if there is one thing I know from that, it's that a motor can run great on the bench, and then crappy under load if something isn't right. This seems to be no different.
#4
B
bertsmobile1
There was an interesting batch of B & S magnetos that appeared on Evilpay down here that were wired backwards or put into the mould upside down
So the instructions cast into the coil ( engine side ) was wrong & they had to be flipped .
I must have has at least 30 of these turn up with owners bemused why their magnetos made no spark .
Thus SOP has always been ry it right way up & if that does not work then upside down .
B
bertsmobile1
And I forgot to mention the coils are polarity sensitive so if fitted upside down they will not workThanks bertsmobile1. I'm reading through the Kohler CV740 book as we speak. And ironically I'm at the ignition coil section. Tomorrow I'm going to look further into that chapter and do some testing like you suggested. It sounds like low (or no) spark is a very good possibility. But then again, so did all the other things I've checked prior to this, so who knows. In the Kohler manual it has a troubleshooting guide for "low engine" power. Every one of their suggestions passes.
Note: I've been out of the Navy for more than 3 decades. But in the last 1 decade I have rebuilt 30+ jet ski motors. And if there is one thing I know from that, it's that a motor can run great on the bench, and then crappy under load if something isn't right. This seems to be no different.
There was an interesting batch of B & S magnetos that appeared on Evilpay down here that were wired backwards or put into the mould upside down
So the instructions cast into the coil ( engine side ) was wrong & they had to be flipped .
I must have has at least 30 of these turn up with owners bemused why their magnetos made no spark .
Thus SOP has always been ry it right way up & if that does not work then upside down .
#5
Turbodriven
Turbodriven
Pulled the dust cover off this morning. What a pain. For a dust cover this thing is bolted stronger than the motor itself. Sheesh.
In any case, are we feeling like this is an issue? I haven't done any multimeter testing yet to the coils but that pickup (?) looks awful crusty. Can I just sand that down to clean it up? Or is it going to need replacing? Coils aren't looking too clean either, but I'll do some Ohm testing to see what they look like.
As a side note, if the pickup needs replacing, what fastener is that holding it on?? Or would I just need a whole new flywheel?
In any case, are we feeling like this is an issue? I haven't done any multimeter testing yet to the coils but that pickup (?) looks awful crusty. Can I just sand that down to clean it up? Or is it going to need replacing? Coils aren't looking too clean either, but I'll do some Ohm testing to see what they look like.
As a side note, if the pickup needs replacing, what fastener is that holding it on?? Or would I just need a whole new flywheel?
Attachments
#6
B
bertsmobile1
B
bertsmobile1
Do not touch them
They are not a set of Barbie doll toys so looking grotty makes no difference to how they work
And no you can not diagnose a faulty magneto coil with you multimeter
Even if you could it would make no difference as they are not repairable
They are not a set of Barbie doll toys so looking grotty makes no difference to how they work
And no you can not diagnose a faulty magneto coil with you multimeter
Even if you could it would make no difference as they are not repairable
#7
Turbodriven
Turbodriven
So wait, then what is this whole chapter for in the Kohler manual then? The whole point of testing is to verify that it's internal workings aren't shorted. If it fails testing then it needs replacing. I know you can't repair them.Do not touch them
They are not a set of Barbie doll toys so looking grotty makes no difference to how they work
And no you can not diagnose a faulty magneto coil with you multimeter
Even if you could it would make no difference as they are not repairable
Attachments
#8
Turbodriven
Turbodriven
Well as I continue down this path I've discoverd that my ignition module gaps were way too small. Kohler books specs .28-.33mm but mine were almost zero. I could barely put my smallest feeler (like aluminum foil thickness) in the gap. In order to set the proper gap I had to clean up both the flywheel pickup and the coil. Lightly with sandpaper. All ohm tests on both coils were perfectly in spec. I'm now at .30mm gaps with a lot less corrosion so we'll see how this affects things.
Gaps too small as I understand it will advance timing though. I know too far retarded timing will cause power loss, not sure about the opposite. We'll see though. Either way I suspect this will improve how the engine runs no matter what. Tomorrow I'll finish buttoning it up and take her for a spin to see. I'll report back.
Gaps too small as I understand it will advance timing though. I know too far retarded timing will cause power loss, not sure about the opposite. We'll see though. Either way I suspect this will improve how the engine runs no matter what. Tomorrow I'll finish buttoning it up and take her for a spin to see. I'll report back.
#9
B
bertsmobile1
B
bertsmobile1
Those particular coils can be tested because they have an external timing module
And there was a series of Kawasaki engines that used external modules although Kawasaki like to call it an Igniter Module
Without serial numbers we do not actually know if your engine has the SAM module, the MDI module or internal chips
The Kohler manual covers all 3 systems because all 3 were used over a period of time that overlapped
Usually Courage's came with the std internal chip while Commands came with any of the 3 systems
However the point remains that they do not need to be cleaned other than to make sure there is no corrosion between the laminations and the mounting pillars so the coil gets a good ground
Magnetism goes through wood , paper plastic & rust \
If it was a problem then the coil wold come painted or plated
And there was a series of Kawasaki engines that used external modules although Kawasaki like to call it an Igniter Module
Without serial numbers we do not actually know if your engine has the SAM module, the MDI module or internal chips
The Kohler manual covers all 3 systems because all 3 were used over a period of time that overlapped
Usually Courage's came with the std internal chip while Commands came with any of the 3 systems
However the point remains that they do not need to be cleaned other than to make sure there is no corrosion between the laminations and the mounting pillars so the coil gets a good ground
Magnetism goes through wood , paper plastic & rust \
If it was a problem then the coil wold come painted or plated
#10
B
bertsmobile1
Closer = bigger spark slightly advanced
further away = smaller spark slightly retarded
In fact you can "tune" the timing by varying the air gap
However the take away is unless the laminations actually make contact with the coil , if it is good it will generate a spark.
B
bertsmobile1
Goes like thisWell as I continue down this path I've discoverd that my ignition module gaps were way too small. Kohler books specs .28-.33mm but mine were almost zero. I could barely put my smallest feeler (like aluminum foil thickness) in the gap. In order to set the proper gap I had to clean up both the flywheel pickup and the coil. Lightly with sandpaper. All ohm tests on both coils were perfectly in spec. I'm now at .30mm gaps with a lot less corrosion so we'll see how this affects things.
Gaps too small as I understand it will advance timing though. I know too far retarded timing will cause power loss, not sure about the opposite. We'll see though. Either way I suspect this will improve how the engine runs no matter what. Tomorrow I'll finish buttoning it up and take her for a spin to see. I'll report back.
Closer = bigger spark slightly advanced
further away = smaller spark slightly retarded
In fact you can "tune" the timing by varying the air gap
However the take away is unless the laminations actually make contact with the coil , if it is good it will generate a spark.
#11
Turbodriven
Turbodriven
No change. Back to the drawing board. Both cylinders are getting good spark (checked).
I did notice something different though. Note that before I did any work, right after I bought this mower I pulled the plugs and the right side was golden brown and the left side was dry soot black. I put new plugs in it and ran around the yard a little bit and as stated earlier both plugs were dry soot black. Not sure how that anomaly happened because I've just done two more clean plug tests and both times the left cylinder comes in dry soot black and the right cylinder comes in white. So, considering this is a single carb engine, there is something definitely wrong with the one of the cylinders for sure. Also considering both cylinders had equal and good compression and both are getting good spark (tested) my gut is telling me it's something with a head? Cams, valves, rockers... dunno? But I need to do a leak down test and/or pull the covers off the heads to check things for sure.
Still looking for answers if anyone has experience here. Getting frustrated...
I did notice something different though. Note that before I did any work, right after I bought this mower I pulled the plugs and the right side was golden brown and the left side was dry soot black. I put new plugs in it and ran around the yard a little bit and as stated earlier both plugs were dry soot black. Not sure how that anomaly happened because I've just done two more clean plug tests and both times the left cylinder comes in dry soot black and the right cylinder comes in white. So, considering this is a single carb engine, there is something definitely wrong with the one of the cylinders for sure. Also considering both cylinders had equal and good compression and both are getting good spark (tested) my gut is telling me it's something with a head? Cams, valves, rockers... dunno? But I need to do a leak down test and/or pull the covers off the heads to check things for sure.
Still looking for answers if anyone has experience here. Getting frustrated...
#12
B
bertsmobile1
B
bertsmobile1
I still think your engine is out of time
If you have a ignition strobe light
Hook it up to one cylinder and take a video of where the magnet is with respect to one of the coil legs
Stop the engine and mark the magnet with a white paint pen
Won't be in exactly the right spot but that will be good enough for this test
Run the engine again with the strobe to confirm the position of the lines .
Then swap over to the other cylinder and see if the lines are in the same position relative to that sides magneto legs .
The other thing that has been overlooked is a leaking inlet manifold est test for that is to run the engine again with the blower cover off and saturate each manifold with liquid WD 40 or similar from a trigger sprayer .
While doing this work the governor by hand from WFO to slow idle for maximum manifold suction
Any leak will show up with a lot of white smoke from the exhaust .
Another thing to check is the actual valve positions
The cam lobes & valves are identical so the protrusion inlet to exhaust and left to right should be identical
While not common with Kohlers , a valve guide can slip in the head if the head gets hot enough to overcome the heat treatment and become soft .
If you have a ignition strobe light
Hook it up to one cylinder and take a video of where the magnet is with respect to one of the coil legs
Stop the engine and mark the magnet with a white paint pen
Won't be in exactly the right spot but that will be good enough for this test
Run the engine again with the strobe to confirm the position of the lines .
Then swap over to the other cylinder and see if the lines are in the same position relative to that sides magneto legs .
The other thing that has been overlooked is a leaking inlet manifold est test for that is to run the engine again with the blower cover off and saturate each manifold with liquid WD 40 or similar from a trigger sprayer .
While doing this work the governor by hand from WFO to slow idle for maximum manifold suction
Any leak will show up with a lot of white smoke from the exhaust .
Another thing to check is the actual valve positions
The cam lobes & valves are identical so the protrusion inlet to exhaust and left to right should be identical
While not common with Kohlers , a valve guide can slip in the head if the head gets hot enough to overcome the heat treatment and become soft .
#13
Turbodriven
Ok, I've dug into your suggestions and have a question at the end.
1. My Kohler has 'Smart-Spark' and I've run the timing advance test per the manual.
2. I've exposed the inlet manifolds and all the nuts are tight at each cylinder head and there doesn't appear to be any gasket issues but I have yet to spray carb cleaner or whatnot to check for vacuum leaks. Based on visual inspection I don't believe this to be any issue but I'll run the test anyways.
3. I pulled both valve covers and rotated the engine a few times. Everything seems tight and functions as it should. I measured the rocker/valve travel on both sides to compare and both are the same with no loose rockers or anything. I can't see anything wrong in there tbh.
Now the question. Back to timing... Isn't the flywheel magnet suppose to be at the ignition coil when its corresponding cylinder is at TDC (or slightly past TDC)? My flywheel magnet is 4" past each when the appropriate cylinder is at TDC. (see cyl1 and cyl2 TDC pics). I could be wrong on this. I just thought the trigger was tied to an immediate firing of that cylinder. And that should happen a few milisecond AFTER the engine is at TDC. So it should all line up at that event. No?
Turbodriven
I still think your engine is out of time
Ok, I've dug into your suggestions and have a question at the end.
1. My Kohler has 'Smart-Spark' and I've run the timing advance test per the manual.
- 1. Make a line near edge of flywheel screen with a marking pen, chalk, or narrow tape.
- 2. Connect an automotive timing light to cylinder that had good spark.
- 3. Run engine at idle and use timing light beam to locate line on screen. Draw a line on blower housing next to line
- on screen. Accelerate to full throttle and watch for movement of line on screen relative to line on blower housing. If
- both cylinders had good spark, repeat test on other cylinder.
2. I've exposed the inlet manifolds and all the nuts are tight at each cylinder head and there doesn't appear to be any gasket issues but I have yet to spray carb cleaner or whatnot to check for vacuum leaks. Based on visual inspection I don't believe this to be any issue but I'll run the test anyways.
3. I pulled both valve covers and rotated the engine a few times. Everything seems tight and functions as it should. I measured the rocker/valve travel on both sides to compare and both are the same with no loose rockers or anything. I can't see anything wrong in there tbh.
Now the question. Back to timing... Isn't the flywheel magnet suppose to be at the ignition coil when its corresponding cylinder is at TDC (or slightly past TDC)? My flywheel magnet is 4" past each when the appropriate cylinder is at TDC. (see cyl1 and cyl2 TDC pics). I could be wrong on this. I just thought the trigger was tied to an immediate firing of that cylinder. And that should happen a few milisecond AFTER the engine is at TDC. So it should all line up at that event. No?
Attachments
#14
C
Cajun power
C
Cajun power
couple suggestions from easy to difficult:
1. check the choke valve...should have a spring that opens that valve when choke is not applied...sometimes the spring is too weak, and sometimes the choke valve is gummy stuck...and so as air is drawn into the carb, it will have a tendency to get sucked into the close position (reducing air flow).....causing the engine to go rich! sluggish performance.
2. check all your safety switches...seat and drive controls...intermittent problems with power can be caused by gummy, loose safety switches or where wiring connections to them are shorting to ground intermittently...inspect all wiring to safety switches and make sure no damage to insulation and connections are solid and no crude. do the shake test while the engine is running.. a little tricky to accomplish but you have to be creative.
3. does your gas have some water in it? disconnect fuel line, drain into a glass container and look for separation.
4. check oil levels...sometimes overfilled causes oil to get into carb from breather and even cause crank pressure problems...check you oil levels...under load an overfilled oil will cause smoke...that's typical.. but always check oil levels.
5. ENGINE OFF - look under the mower and inspect all blades, spindles and pto...make sure unloaded all spindles are not seized, including tensioner pulley..if there is something wrapped up around a wheel or both, can cause excessive loads.
6. take all spark plugs OUT...rotate engine by hand..should rotate easily and little resistance. if it's hard to turn with spark plugs out, you need to address that and find out what is causing it. (valves, crank, piston, rings, etc)
7. hand test the governor while engine is running..it should return automatically after release.
8. head cylinder gasket failure...engine running, shroud off, spray a little carb cleaner near each head cylinder...any change in rpm indicates loss of power due to gasket failure...classically a very small blow by and loss of power can happen only under load and in a hot cycle.
just some ideas to run through
1. check the choke valve...should have a spring that opens that valve when choke is not applied...sometimes the spring is too weak, and sometimes the choke valve is gummy stuck...and so as air is drawn into the carb, it will have a tendency to get sucked into the close position (reducing air flow).....causing the engine to go rich! sluggish performance.
2. check all your safety switches...seat and drive controls...intermittent problems with power can be caused by gummy, loose safety switches or where wiring connections to them are shorting to ground intermittently...inspect all wiring to safety switches and make sure no damage to insulation and connections are solid and no crude. do the shake test while the engine is running.. a little tricky to accomplish but you have to be creative.
3. does your gas have some water in it? disconnect fuel line, drain into a glass container and look for separation.
4. check oil levels...sometimes overfilled causes oil to get into carb from breather and even cause crank pressure problems...check you oil levels...under load an overfilled oil will cause smoke...that's typical.. but always check oil levels.
5. ENGINE OFF - look under the mower and inspect all blades, spindles and pto...make sure unloaded all spindles are not seized, including tensioner pulley..if there is something wrapped up around a wheel or both, can cause excessive loads.
6. take all spark plugs OUT...rotate engine by hand..should rotate easily and little resistance. if it's hard to turn with spark plugs out, you need to address that and find out what is causing it. (valves, crank, piston, rings, etc)
7. hand test the governor while engine is running..it should return automatically after release.
8. head cylinder gasket failure...engine running, shroud off, spray a little carb cleaner near each head cylinder...any change in rpm indicates loss of power due to gasket failure...classically a very small blow by and loss of power can happen only under load and in a hot cycle.
just some ideas to run through
#15
Turbodriven
Turbodriven
Thanks Cajun. All good suggestions. I'll run through the ones I haven't done yet. I've done a lot more testing but stopped posting in this thread for a few days so some of these things already "passed". At this point I'm 100% sure my ignition system is good based on further tests. Everything looks normal with the valve covers off and rotating the engine. Really the only thing it could be at this point is a head gasket or rings (or a binding drive system that externally taxes the motor). The part I can't get around is that I'm getting 160+psi compression numbers though. The mower has 1200 hours on it (I can only assume I'm on the current motor?) so no matter what an overhaul can't hurt at this point. I ordered new head gaskets which were super cheap. I may just pull the heads and see what I see. A hone and ring job couldn't hurt at 1200 hours too and that sort of thing doesn't scare me. Rings are fairly cheap too so it'd be a good investment no matter what at 1200hrs. I enjoy rebuilding engines and this is an easy one so we'll see. But maybe with the heads off I see a blown out oil galley and that'll explain things. *shrug.
#16
O
ohiodave53
O
ohiodave53
Learned a good lesson about after market Chinese parts after much aggravation with a Husky chainsaw.
Bought a replacement coil/"ignition module" on the cheap from the A online site. Looked like the old one so after installing the saw would not fire even on a shot of starting fluid. Checked for spark with inline tester and looked fine. So there I am pulling my hair out...good compression, good fuel and what I think is good spark. After much aggravation I got back online, ordered a genuine OEM coil (yeah, it cost at least twice what the china junk did). Installed it and put the saw back together, set the choke/throttle, about the 3rd pull away she goes and been using it since.
Bought a replacement coil/"ignition module" on the cheap from the A online site. Looked like the old one so after installing the saw would not fire even on a shot of starting fluid. Checked for spark with inline tester and looked fine. So there I am pulling my hair out...good compression, good fuel and what I think is good spark. After much aggravation I got back online, ordered a genuine OEM coil (yeah, it cost at least twice what the china junk did). Installed it and put the saw back together, set the choke/throttle, about the 3rd pull away she goes and been using it since.
#17
C
Cajun power
C
Cajun power
couple suggestions from easy to difficult:
1. check the choke valve...should have a spring that opens that valve when choke is not applied...sometimes the spring is too weak, and sometimes the choke valve is gummy stuck...and so as air is drawn into the carb, it will have a tendency to get sucked into the close position (reducing air flow).....causing the engine to go rich! sluggish performance.
2. check all your safety switches...seat and drive controls...intermittent problems with power can be caused by gummy, loose safety switches or where wiring connections to them are shorting to ground...inspect all wiring to safety switches and make sure no damage to insulation and connections are solid and no crude.
3. does your gas have some water in it? disconnect fuel line, drain into a glass container and look for separation.
4. check oil levels...sometimes overfilled causes oil to get into carb from breather and even cause crank pressure problems...check you oil levels...under load an overfilled oil will cause smoke...that's typical.. but always check oil levels.
5. ENGINE OFF - look under the mower and inspect all blades, spindles and pto...make sure unloaded all spindles are not seized, including tensioner pulley..if there is something wrapped up around a wheel or both, can cause excessive loads.
6. take all spark plugs OUT...rotate engine by hand..should rotate easily and little resistance. if it's hard to turn with spark plugs out, you need to address that and find out what is causing it. (valves, crank, piston, rings, etc)
7.
I recently did a head cylinder gaskets replace on a kawasaki fr691V (after chasing ghosts - symptoms was a surging engine at all RPM's). I opted for all copper gaskets (better squish and heat transfer), over the kawa oem gaskets.
I like rebuilding also. It's a side hustle to repair mowers and other small engine machines.
1. check the choke valve...should have a spring that opens that valve when choke is not applied...sometimes the spring is too weak, and sometimes the choke valve is gummy stuck...and so as air is drawn into the carb, it will have a tendency to get sucked into the close position (reducing air flow).....causing the engine to go rich! sluggish performance.
2. check all your safety switches...seat and drive controls...intermittent problems with power can be caused by gummy, loose safety switches or where wiring connections to them are shorting to ground...inspect all wiring to safety switches and make sure no damage to insulation and connections are solid and no crude.
3. does your gas have some water in it? disconnect fuel line, drain into a glass container and look for separation.
4. check oil levels...sometimes overfilled causes oil to get into carb from breather and even cause crank pressure problems...check you oil levels...under load an overfilled oil will cause smoke...that's typical.. but always check oil levels.
5. ENGINE OFF - look under the mower and inspect all blades, spindles and pto...make sure unloaded all spindles are not seized, including tensioner pulley..if there is something wrapped up around a wheel or both, can cause excessive loads.
6. take all spark plugs OUT...rotate engine by hand..should rotate easily and little resistance. if it's hard to turn with spark plugs out, you need to address that and find out what is causing it. (valves, crank, piston, rings, etc)
7.
before you make a big investment, I would look at any kind of crack in the crank, case, head cylinder. Sometimes you get these really small fine cracks that do not reveal until a high heat cycle and under load. A standard dye penetrate with blue light should reveal that. But will need to clean the engine up really well. Failed head cylinder gaskets will NOT fail a compression test. a leak down test "CAN" help identify a head cylinder gasket leak! (as well as many other things)Thanks Cajun. All good suggestions. I'll run through the ones I haven't done yet. I've done a lot more testing but stopped posting in this thread for a few days so some of these things already "passed". At this point I'm 100% sure my ignition system is good based on further tests. Everything looks normal with the valve covers off and rotating the engine. Really the only thing it could be at this point is a head gasket or rings (or a binding drive system that externally taxes the motor). The part I can't get around is that I'm getting 160+psi compression numbers though. The mower has 1200 hours on it (I can only assume I'm on the current motor?) so no matter what an overhaul can't hurt at this point. I ordered new head gaskets which were super cheap. I may just pull the heads and see what I see. A hone and ring job couldn't hurt at 1200 hours too and that sort of thing doesn't scare me. Rings are fairly cheap too so it'd be a good investment no matter what at 1200hrs. I enjoy rebuilding engines and this is an easy one so we'll see. But maybe with the heads off I see a blown out oil galley and that'll explain things. *shrug.
I recently did a head cylinder gaskets replace on a kawasaki fr691V (after chasing ghosts - symptoms was a surging engine at all RPM's). I opted for all copper gaskets (better squish and heat transfer), over the kawa oem gaskets.
I like rebuilding also. It's a side hustle to repair mowers and other small engine machines.
#18
M
MowerNick
M
MowerNick
Try pulling your plug wires with rubber handle pliers while its running. If you pull one and it stalls then that side is your problem. Most likely no spark on one side. Surprisingly those kohlers run fairly well on one cylinder until its time to work.
#19
Turbodriven
Turbodriven
Thanks. I'm miles past that though. It passed that test. Coils also passed all Kohler manual ohm tests. I rechecked timing per the manual and it passed. And I swapped coils left to right (verifying gaps too) with no change in the cylinder that was running rich. I'm near 100% sure my coils and the entire ignition system is working properly.Try pulling your plug wires with rubber handle pliers while its running. If you pull one and it stalls then that side is your problem. Most likely no spark on one side. Surprisingly those kohlers run fairly well on one cylinder until its time to work.
#20
M
moparjoe
M
moparjoe
Shorten the governor spring.Hey everyone. I'm new to zero turns but very mechanical in experience (ex Navy fighter jet mechanic).
Got a used 2005 260z (Kohler CV740 Command Pro 27) for cheap that starts and idles (and throttles up and down) perfect. Sounds good sitting still. Even starts mowing like a bat out of hell for the first few seconds. But then after 20 feet of moving at speed (and even worse when blades are engaged) the motor quickly starts winding down to about 20-30% rpms (or so it feels) and barely mows. Like someone stuck a banana in the tailpipe. If I disengage blades and pull back the controls to a stop, the rpms pick back up and she idles/sounds normal again. But then the behavior returns when I push the sticks forward.
I put new plugs in it and after mowing for five minutes I pulled both plugs out and they were both dry and thick black (rich).
1. This behavior remains unchanged after installing a brand new carburetor, new fuel pump, fuel filter, spark plugs, air filter, and fresh gas.
2. Compression tests on cyl1=170psi and cyl2=175psi
3. There is no smoke in the oil dipstick (crankcase) after running and the oil level is correct.
4. Behavior does not correct when unscrewing the gas cap (*even though "lean" doesn't appear to be the issue)
5. Governor linkage was set per specs when I installed the new carb.
6. Battery is good and I hooked up my multimeter while running and it maintains 13.x+ volts throughout the whole behavior. Also, there is no spikes when engaging PTO clutch. That system appears to be operating normal??
7. I had the deck off last week and all three spindles seem to spin fine.
I'm not sure what else to think. The basic behavior is that the motor slows down under load. So either the normal load is affecting something wrong with the motor, or an abnormally heavy load is too great for the healthy motor.
Any ideas on what to check or fix to get this right?
#21
D
Davenj4f
D
Davenj4f
Check your spindles for wear. If they have any play, the mower will bog down under a load. I just went thru that on my mower. Also, a VERY dirty air filter will produce the same effect.Hey everyone. I'm new to zero turns but very mechanical in experience (ex Navy fighter jet mechanic).
Got a used 2005 260z (Kohler CV740 Command Pro 27) for cheap that starts and idles (and throttles up and down) perfect. Sounds good sitting still. Even starts mowing like a bat out of hell for the first few seconds. But then after 20 feet of moving at speed (and even worse when blades are engaged) the motor quickly starts winding down to about 20-30% rpms (or so it feels) and barely mows. Like someone stuck a banana in the tailpipe. If I disengage blades and pull back the controls to a stop, the rpms pick back up and she idles/sounds normal again. But then the behavior returns when I push the sticks forward.
I put new plugs in it and after mowing for five minutes I pulled both plugs out and they were both dry and thick black (rich).
1. This behavior remains unchanged after installing a brand new carburetor, new fuel pump, fuel filter, spark plugs, air filter, and fresh gas.
2. Compression tests on cyl1=170psi and cyl2=175psi
3. There is no smoke in the oil dipstick (crankcase) after running and the oil level is correct.
4. Behavior does not correct when unscrewing the gas cap (*even though "lean" doesn't appear to be the issue)
5. Governor linkage was set per specs when I installed the new carb.
6. Battery is good and I hooked up my multimeter while running and it maintains 13.x+ volts throughout the whole behavior. Also, there is no spikes when engaging PTO clutch. That system appears to be operating normal??
7. I had the deck off last week and all three spindles seem to spin fine.
I'm not sure what else to think. The basic behavior is that the motor slows down under load. So either the normal load is affecting something wrong with the motor, or an abnormally heavy load is too great for the healthy motor.
Any ideas on what to check or fix to get this right?
#22
T
TobyU
It's running on the one you pulled when pulling it makes it die so the other one was doing nothing.
T
TobyU
Don't you mean if you pull one and it stalls... Then the other side is the problem??Try pulling your plug wires with rubber handle pliers while its running. If you pull one and it stalls then that side is your problem. Most likely no spark on one side. Surprisingly those kohlers run fairly well on one cylinder until its time to work.
It's running on the one you pulled when pulling it makes it die so the other one was doing nothing.
#24
Turbodriven
Turbodriven
The idea is that if somehow your mower is running on only one cylinder, you wouldn't necessarily notice it outright as it will still run and sound fairly ok with no load. But to check for this, you pull one spark plug cable (say the #1) and if by doing so the mower shuts down, then you know the #2 cyl wasn't working (as you can run on one but not on zero cylinders).Don't you mean if you pull one and it stalls... Then the other side is the problem??
It's running on the one you pulled when pulling it makes it die so the other one was doing nothing.
#25
Turbodriven
Turbodriven
As a follow up (hopefully to close the thread) I've narrowed my motor problems down to either rings, valves or a head gasket issue (despite having good compression). Everything else has been looked at and tested good, so I pulled the heads. My valves are sealing and within specs in all ways. Cylinders look good with visible cross hatching still after 1200 hrs (what!!?). My #2 head gasket seemed to be ok too. But the (OEM) #1 head gasket had some carbon tracking on the exhaust side fins which I guess is a typical failure. However, the head gasket itself didn't look that bad to be honest. But I checked flatness, both well within specs, then put updated gaskets in and buttoned it up per manual specs.
As an interesting note... in this process I also discovered that my 5 rib hydro drive belt was missing 2 of the 5 ribs, just disintegrated. I'm sure under load it was struggling to hook up. This may have been at least part of my problem. New belt was delivered last night so I'll put it on and see how things go with the new head gaskets and new belt installed. Fingers crossed!
As an interesting note... in this process I also discovered that my 5 rib hydro drive belt was missing 2 of the 5 ribs, just disintegrated. I'm sure under load it was struggling to hook up. This may have been at least part of my problem. New belt was delivered last night so I'll put it on and see how things go with the new head gaskets and new belt installed. Fingers crossed!
#26
T
TobyU
As you just clarified, if you pull one off and it stalls, it was the other one that wasn't giving you power so that one would be your problem.
T
TobyU
The idea is that if somehow your mower is running on only one cylinder, you wouldn't necessarily notice it outright as it will still run and sound fairly ok with no load. But to check for this, you pull one spark plug cable (say the #1) and if by doing so the mower shuts down, then you know the #2 cyl wasn't working (as you can run on one but not on zero cylinders).
Precisely what I said. I believe you misspoke in your first statement when you said if you pull a spark plug wire off and it stalls then that one is your problem.The idea is that if somehow your mower is running on only one cylinder, you wouldn't necessarily notice it outright as it will still run and sound fairly ok with no load. But to check for this, you pull one spark plug cable (say the #1) and if by doing so the mower shuts down, then you know the #2 cyl wasn't working (as you can run on one but not on zero cylind
As you just clarified, if you pull one off and it stalls, it was the other one that wasn't giving you power so that one would be your problem.
#27
T
TobyU
I'm sorry to say I feel your diagnostic procedure has been all over the place and throwing a lot of time and parts into the engine that I would have never done.
It does no good to troubleshoot and diagnose certain aspects of things unless you first are stepping back and making educated guess on what the potential problem could be in the first place.
In other words if a lawn mower had some sort of noise in it only when you turn on the blades then it would be senseless to first start out worrying about the engine causing the noise and I understand this is not quite that simple because it is certainly an engine thing AND not to say that a noise problem with the blades on couldn't be coming from the engine or engine related because I have seen that happen too but it's highly unlikely.
T
TobyU
Well, your belt has nothing to do with your engine in any way shape or form. Now the machine could very well slow down going uphill if your bell to slipping etc but your engine RPM and sound wouldn't change in any way.As a follow up (hopefully to close the thread) I've narrowed my motor problems down to either rings, valves or a head gasket issue (despite having good compression). Everything else has been looked at and tested good, so I pulled the heads. My valves are sealing and within specs in all ways. Cylinders look good with visible cross hatching still after 1200 hrs (what!!?). My #2 head gasket seemed to be ok too. But the (OEM) #1 head gasket had some carbon tracking on the exhaust side fins which I guess is a typical failure. However, the head gasket itself didn't look that bad to be honest. But I checked flatness, both well within specs, then put updated gaskets in and buttoned it up per manual specs.
As an interesting note... in this process I also discovered that my 5 rib hydro drive belt was missing 2 of the 5 ribs, just disintegrated. I'm sure under load it was struggling to hook up. This may have been at least part of my problem. New belt was delivered last night so I'll put it on and see how things go with the new head gaskets and new belt installed. Fingers crossed!
I'm sorry to say I feel your diagnostic procedure has been all over the place and throwing a lot of time and parts into the engine that I would have never done.
It does no good to troubleshoot and diagnose certain aspects of things unless you first are stepping back and making educated guess on what the potential problem could be in the first place.
In other words if a lawn mower had some sort of noise in it only when you turn on the blades then it would be senseless to first start out worrying about the engine causing the noise and I understand this is not quite that simple because it is certainly an engine thing AND not to say that a noise problem with the blades on couldn't be coming from the engine or engine related because I have seen that happen too but it's highly unlikely.
#28
Turbodriven
As far as diagnosing, I think I've been very methodical. Starting with the fuel system, then moving to electrical, and then the engine. Checking each system per the manual from front to back. Maybe my list was a bit jumbled. But I'm not a writer. And I rather enjoy tinkering on engines. So the time is a non-issue.
For what it's worth, my problem still isn't solved and I'm open to any ideas. I hooked a tinytach up to it while mowing my lawn an hour ago and when under normal load, the rpms dip to about 1700-2000. Occasionally less, and sometimes it holds at 2500 for a short while (depends on load). But at rest idle is 1200rpm and full throttle is 3700-3900rpm.
You're right about listening to the problem though. But that's what is so frustrating here. The problem is telling me there is a fuel/air mixture problem between Cyl1 and Cyl2 but nothing seems to be wrong anything that could cause that. Good compression both sides. Good valves both sides. New head gaskets both sides. Good coils both sides (even swapped them after testing them with no change) and I'm still getting rich plugs on cyl1 only (and possibly lean on cyl2). Plugs in pic are today after a full mow. Plugs were clean white when starting.
Turbodriven
I respectfully disagree. To begin with, not including the parts the mower actually needed (like new filters, belt, etc) I've only spent about $46 on this $600 mower. And most of that was on a new carb. Mostly because I just needed the gaskets it came with after tearing the ones on the mower. I figured the delta between just new gaskets and a whole new carb with gaskets was worth the few extra dollars.I'm sorry to say I feel your diagnostic procedure has been all over the place and throwing a lot of time and parts into the engine that I would have never done.
It does no good to troubleshoot and diagnose certain aspects of things unless you first are stepping back and making educated guess on what the potential problem could be in the first place.
In other words if a lawn mower had some sort of noise in it only when you turn on the blades then it would be senseless to first start out worrying about the engine causing the noise and I understand this is not quite that simple because it is certainly an engine thing AND not to say that a noise problem with the blades on couldn't be coming from the engine or engine related because I have seen that happen too but it's highly unlikely.
As far as diagnosing, I think I've been very methodical. Starting with the fuel system, then moving to electrical, and then the engine. Checking each system per the manual from front to back. Maybe my list was a bit jumbled. But I'm not a writer. And I rather enjoy tinkering on engines. So the time is a non-issue.
For what it's worth, my problem still isn't solved and I'm open to any ideas. I hooked a tinytach up to it while mowing my lawn an hour ago and when under normal load, the rpms dip to about 1700-2000. Occasionally less, and sometimes it holds at 2500 for a short while (depends on load). But at rest idle is 1200rpm and full throttle is 3700-3900rpm.
You're right about listening to the problem though. But that's what is so frustrating here. The problem is telling me there is a fuel/air mixture problem between Cyl1 and Cyl2 but nothing seems to be wrong anything that could cause that. Good compression both sides. Good valves both sides. New head gaskets both sides. Good coils both sides (even swapped them after testing them with no change) and I'm still getting rich plugs on cyl1 only (and possibly lean on cyl2). Plugs in pic are today after a full mow. Plugs were clean white when starting.
Attachments
#29
T
TobyU
I don't care that something was old and needed to replaced anyways or was likely to fail etc etc. To me that's just a cop out..
I don't replace anything until it's broken or until it fails.
But I'm a cheapskate, and my goal is to get to the bottom of the problem and get the equipment running properly as quickly and as cheaply as possible.
That is the first concern..
Any additional concerns about longevity or how many times it's going to mow for is the secondary consideration which we can talk about later.
Regardless, since your problem still isn't fixed, your two new plugs you put in and after one mow showing that way definitely says something is still awry.
That number one plug is certainly too rich or possibly it's not firing all the time but that's not the only possibilities.
The other one could be a little lean but it could also be fine..
I wouldn't really worry about that one for now.
If I remember correctly this is a Briggs & Stratton twin but please correct me if I'm wrong because it's been a number of days and this thread is over three pages long.
I guess it doesn't make much different among the common brands but about the only ways I can think of off the top of my head that would be common for that plug to be that carbon footed up after only one mow of an hour or so would be extremely low air flow which is kind of hard to do on a twin since they share the same carburetor and intake and would be much more simple to happen on a single....then the second way would be if the plug just simply isn't firing every time it's supposed to, and the third would be a leaky head gasket or some other head or even valve problem.
It's not worth delving into the thought process right now as the which is more likely or what causes what and how.
The best procedure from here is to start with the easiest thing or anything you can 100% eliminate and then move on..
A lot of times the problem is people check something and rule it out but they haven't 100% ruled it out and often it ends up being part of the problem or the whole problem later.
So again, I would go back to cancelling out cylinders.
If I had to guess I would say when you take off that number one sooty plug wire, the engine still runs pretty decently on the other one.
Then, when you take off the number two plug wire which is much cleaner I believe you'll find there is a more drastic change and you're getting lower power from that number one cylinder.
Heck, my guess could be wrong and it could be reversed because maybe the number two cylinder plug is so clean because it's not getting any combustion at all but I doubt that.
So again, it all boils down to a performance test of how it runs on each cylinder or even if it runs on each cylinder.
So this would be more akin to a cylinder balance test they call it in the automotive field.
As I said, a compression tester is pretty much useless on these and I haven't screwed one into a machine in over 20 years and I do well over a thousand of these engines a year.
A link down test or simply but, blowing air through the cylinder and moving the Piston to a certain place so the valves move will tell you some, but I still feel it's a waste of time as there's more things you can do quicker and easier to get things diagnosed.
So do this cylinder canceling out test and report back with the findings..
I used to be an auto mechanic more so than a lawn mower mechanic so the first time I adjusted the valves on a Briggs & stratton, I didn't incorrectly and it wouldn't run right and when I checked them again I found I had one extremely too loose.
I find that people with other training like Auto mechanics, aviation, boats, or engineers, often have a hard time working on lawn mowers and often do things the very roundabout, hard, or time-consuming way.
I have streamlined the number of procedures that I actually do to mowers down to a science of quickness and repetition.
So basically, I am efficient as hell.
Often, the way I do it is a little bit harder and more convoluted as far as working blindly or in a tight area etc but it allows me to get the job done far quicker than your average YouTube person who takes everything apart and lays it on their work bench and everything like that.
I don't have time for that.
I have been come quite a master diagnostician but I will say it's very hard to diagnose things second hand and via text messaging etc and only a little bit easier when you're doing it via Skype or video..
There's nothing like getting a machine in front of a well experienced ear and set of eyes to quickly narrow down where the problem is coming from.
T
TobyU
Well, the attitude is going to come out here but you can disagree all you want but all I'm saying is if that lawn mower was in front of me I would have been to the bottom of diagnosing it before I replaced a single part.I respectfully disagree. To begin with, not including the parts the mower actually needed (like new filters, belt, etc) I've only spent about $46 on this $600 mower. And most of that was on a new carb. Mostly because I just needed the gaskets it came with after tearing the ones on the mower. I figured the delta between just new gaskets and a whole new carb with gaskets was worth the few extra dollars.
As far as diagnosing, I think I've been very methodical. Starting with the fuel system, then moving to electrical, and then the engine. Checking each system per the manual from front to back. Maybe my list was a bit jumbled. But I'm not a writer. And I rather enjoy tinkering on engines. So the time is a non-issue.
For what it's worth, my problem still isn't solved and I'm open to any ideas. I hooked a tinytach up to it while mowing my lawn an hour ago and when under normal load, the rpms dip to about 1700-2000. Occasionally less, and sometimes it holds at 2500 for a short while (depends on load). But at rest idle is 1200rpm and full throttle is 3700-3900rpm.
You're right about listening to the problem though. But that's what is so frustrating here. The problem is telling me there is a fuel/air mixture problem between Cyl1 and Cyl2 but nothing seems to be wrong anything that could cause that. Good compression both sides. Good valves both sides. New head gaskets both sides. Good coils both sides (even swapped them after testing them with no change) and I'm still getting rich plugs on cyl1 only (and possibly lean on cyl2). Plugs in pic are today after a full mow. Plugs were clean white when starting.
I don't care that something was old and needed to replaced anyways or was likely to fail etc etc. To me that's just a cop out..
I don't replace anything until it's broken or until it fails.
But I'm a cheapskate, and my goal is to get to the bottom of the problem and get the equipment running properly as quickly and as cheaply as possible.
That is the first concern..
Any additional concerns about longevity or how many times it's going to mow for is the secondary consideration which we can talk about later.
Regardless, since your problem still isn't fixed, your two new plugs you put in and after one mow showing that way definitely says something is still awry.
That number one plug is certainly too rich or possibly it's not firing all the time but that's not the only possibilities.
The other one could be a little lean but it could also be fine..
I wouldn't really worry about that one for now.
If I remember correctly this is a Briggs & Stratton twin but please correct me if I'm wrong because it's been a number of days and this thread is over three pages long.
I guess it doesn't make much different among the common brands but about the only ways I can think of off the top of my head that would be common for that plug to be that carbon footed up after only one mow of an hour or so would be extremely low air flow which is kind of hard to do on a twin since they share the same carburetor and intake and would be much more simple to happen on a single....then the second way would be if the plug just simply isn't firing every time it's supposed to, and the third would be a leaky head gasket or some other head or even valve problem.
It's not worth delving into the thought process right now as the which is more likely or what causes what and how.
The best procedure from here is to start with the easiest thing or anything you can 100% eliminate and then move on..
A lot of times the problem is people check something and rule it out but they haven't 100% ruled it out and often it ends up being part of the problem or the whole problem later.
So again, I would go back to cancelling out cylinders.
If I had to guess I would say when you take off that number one sooty plug wire, the engine still runs pretty decently on the other one.
Then, when you take off the number two plug wire which is much cleaner I believe you'll find there is a more drastic change and you're getting lower power from that number one cylinder.
Heck, my guess could be wrong and it could be reversed because maybe the number two cylinder plug is so clean because it's not getting any combustion at all but I doubt that.
So again, it all boils down to a performance test of how it runs on each cylinder or even if it runs on each cylinder.
So this would be more akin to a cylinder balance test they call it in the automotive field.
As I said, a compression tester is pretty much useless on these and I haven't screwed one into a machine in over 20 years and I do well over a thousand of these engines a year.
A link down test or simply but, blowing air through the cylinder and moving the Piston to a certain place so the valves move will tell you some, but I still feel it's a waste of time as there's more things you can do quicker and easier to get things diagnosed.
So do this cylinder canceling out test and report back with the findings..
I used to be an auto mechanic more so than a lawn mower mechanic so the first time I adjusted the valves on a Briggs & stratton, I didn't incorrectly and it wouldn't run right and when I checked them again I found I had one extremely too loose.
I find that people with other training like Auto mechanics, aviation, boats, or engineers, often have a hard time working on lawn mowers and often do things the very roundabout, hard, or time-consuming way.
I have streamlined the number of procedures that I actually do to mowers down to a science of quickness and repetition.
So basically, I am efficient as hell.
Often, the way I do it is a little bit harder and more convoluted as far as working blindly or in a tight area etc but it allows me to get the job done far quicker than your average YouTube person who takes everything apart and lays it on their work bench and everything like that.
I don't have time for that.
I have been come quite a master diagnostician but I will say it's very hard to diagnose things second hand and via text messaging etc and only a little bit easier when you're doing it via Skype or video..
There's nothing like getting a machine in front of a well experienced ear and set of eyes to quickly narrow down where the problem is coming from.
#30
Turbodriven
https://www.lawnmowerforum.com/threads/cv740-27hp-bogs-severely-under-average-load.75051/
It's becoming a long thread with an ex-Kohler mechanic at the heart of it with me. We've ruled out so many things. I'm at my absolute wits end with this thing and just decided to tear it apart at this point and rebuilt it from the ground up. If you dig into that thread you'll see why I chose that path. I've never been very good at giving up. LOL. Much to my detriment sometimes.
That said, I'm much like you. A cheapskate. And honestly I spent the money on filters/belts/etc before I realized I had a problem. But as far as the problem itself, I'm 100% onboard with don't spend money on a part unless you know it is the problem. But even getting into the engine to find a problem sometimes generates costs (gaskets, seals, etc). I pulled the carbs to clean them and ripped a few gaskets because they were glued on essentially. Gotta buy new gaskets now to put the carb back on and see if it's now fixed. That's money spent on parts that didn't fix the problem. Additionally, some parts just can't be tested accurately. Like my DSAM box. I have no one near me that has a DSAM testing tool. And even if I did they aren't always accurate. And a bad DSAM made 100% sense considering all the other things it wasn't. I jump started this mower a few times too which is reported to kill is Smart Spark box sometimes. After trying everything else, and with the symptoms matched the potential bad part, I spent money on the MDI conversion. It of course didn't fix it though.
In the end my goal is to have a motor/mower that will last me years. An investment. Outside of a hole in the case, there isn't much that can't be fixed on these things. And with such a small initial investment there is a lot of wiggle room before I'm anywhere near upside down on it. I guess that's my train of though in most of my projects. Will I be upside down if I spend this? If not, then let's get her done...
Turbodriven
Thanks for the response. A few weeks ago I moved this to the Kohler forum and streamlined the long list of things I've ruled out. Since they were all kind of all over the place here.Well, the attitude is going to come out here but you can disagree all you want but all I'm saying is if that lawn mower was in front of me I would have been to the bottom of diagnosing it before I replaced a single part.
I don't care that something was old and needed to replaced anyways or was likely to fail etc etc. To me that's just a cop out..
I don't replace anything until it's broken or until it fails.
But I'm a cheapskate, and my goal is to get to the bottom of the problem and get the equipment running properly as quickly and as cheaply as possible.
That is the first concern..
Any additional concerns about longevity or how many times it's going to mow for is the secondary consideration which we can talk about later.
Regardless, since your problem still isn't fixed, your two new plugs you put in and after one mow showing that way definitely says something is still awry.
That number one plug is certainly too rich or possibly it's not firing all the time but that's not the only possibilities.
The other one could be a little lean but it could also be fine..
I wouldn't really worry about that one for now.
If I remember correctly this is a Briggs & Stratton twin but please correct me if I'm wrong because it's been a number of days and this thread is over three pages long.
I guess it doesn't make much different among the common brands but about the only ways I can think of off the top of my head that would be common for that plug to be that carbon footed up after only one mow of an hour or so would be extremely low air flow which is kind of hard to do on a twin since they share the same carburetor and intake and would be much more simple to happen on a single....then the second way would be if the plug just simply isn't firing every time it's supposed to, and the third would be a leaky head gasket or some other head or even valve problem.
It's not worth delving into the thought process right now as the which is more likely or what causes what and how.
The best procedure from here is to start with the easiest thing or anything you can 100% eliminate and then move on..
A lot of times the problem is people check something and rule it out but they haven't 100% ruled it out and often it ends up being part of the problem or the whole problem later.
So again, I would go back to cancelling out cylinders.
If I had to guess I would say when you take off that number one sooty plug wire, the engine still runs pretty decently on the other one.
Then, when you take off the number two plug wire which is much cleaner I believe you'll find there is a more drastic change and you're getting lower power from that number one cylinder.
Heck, my guess could be wrong and it could be reversed because maybe the number two cylinder plug is so clean because it's not getting any combustion at all but I doubt that.
So again, it all boils down to a performance test of how it runs on each cylinder or even if it runs on each cylinder.
So this would be more akin to a cylinder balance test they call it in the automotive field.
As I said, a compression tester is pretty much useless on these and I haven't screwed one into a machine in over 20 years and I do well over a thousand of these engines a year.
A link down test or simply but, blowing air through the cylinder and moving the Piston to a certain place so the valves move will tell you some, but I still feel it's a waste of time as there's more things you can do quicker and easier to get things diagnosed.
So do this cylinder canceling out test and report back with the findings..
I used to be an auto mechanic more so than a lawn mower mechanic so the first time I adjusted the valves on a Briggs & stratton, I didn't incorrectly and it wouldn't run right and when I checked them again I found I had one extremely too loose.
I find that people with other training like Auto mechanics, aviation, boats, or engineers, often have a hard time working on lawn mowers and often do things the very roundabout, hard, or time-consuming way.
I have streamlined the number of procedures that I actually do to mowers down to a science of quickness and repetition.
So basically, I am efficient as hell.
Often, the way I do it is a little bit harder and more convoluted as far as working blindly or in a tight area etc but it allows me to get the job done far quicker than your average YouTube person who takes everything apart and lays it on their work bench and everything like that.
I don't have time for that.
I have been come quite a master diagnostician but I will say it's very hard to diagnose things second hand and via text messaging etc and only a little bit easier when you're doing it via Skype or video..
There's nothing like getting a machine in front of a well experienced ear and set of eyes to quickly narrow down where the problem is coming from.
https://www.lawnmowerforum.com/threads/cv740-27hp-bogs-severely-under-average-load.75051/
It's becoming a long thread with an ex-Kohler mechanic at the heart of it with me. We've ruled out so many things. I'm at my absolute wits end with this thing and just decided to tear it apart at this point and rebuilt it from the ground up. If you dig into that thread you'll see why I chose that path. I've never been very good at giving up. LOL. Much to my detriment sometimes.
That said, I'm much like you. A cheapskate. And honestly I spent the money on filters/belts/etc before I realized I had a problem. But as far as the problem itself, I'm 100% onboard with don't spend money on a part unless you know it is the problem. But even getting into the engine to find a problem sometimes generates costs (gaskets, seals, etc). I pulled the carbs to clean them and ripped a few gaskets because they were glued on essentially. Gotta buy new gaskets now to put the carb back on and see if it's now fixed. That's money spent on parts that didn't fix the problem. Additionally, some parts just can't be tested accurately. Like my DSAM box. I have no one near me that has a DSAM testing tool. And even if I did they aren't always accurate. And a bad DSAM made 100% sense considering all the other things it wasn't. I jump started this mower a few times too which is reported to kill is Smart Spark box sometimes. After trying everything else, and with the symptoms matched the potential bad part, I spent money on the MDI conversion. It of course didn't fix it though.
In the end my goal is to have a motor/mower that will last me years. An investment. Outside of a hole in the case, there isn't much that can't be fixed on these things. And with such a small initial investment there is a lot of wiggle room before I'm anywhere near upside down on it. I guess that's my train of though in most of my projects. Will I be upside down if I spend this? If not, then let's get her done...
#31
Turbodriven
There is also a video of it starting at idling (low and high), and of it running and dropping rpms in post #31
Turbodriven
The test results of this are in post #32 and a follow up in post #46 in the Kohler thread I linked to above.So do this cylinder canceling out test and report back with the findings..
There is also a video of it starting at idling (low and high), and of it running and dropping rpms in post #31