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New CV740 doesn't reach RPM at full throttle
#1
C
c5vettster
C
c5vettster
I am repowering Gravely Z 252 mower model 992071. It originally came with a 27hp CV740 and I found a NOS replacement that is exact with exception of newer ignition module. The new engine is CV740-0020. The older engine is CV740-011. I had to come up with a new wiring harness. The carburetor + ignition box are now powered from a tractor pin that was marked for carburetor but was previously unused. The other engine carb was wired to the regulator line + the starter wire. I think I wired everything correctly. The engine starts easily and shuts down with the key. However, it doesn't go up in RPM. I've check and both the throttle and choke are wide open. The limiter screw appears to have no effect so to speak. But the engine only goes up to ~2500 RMP at WOT. I can't figure out where my problems are. Do you think the voltage on the ignition box maybe unstable? I tried wiriting it directly to the positive terminal and it didn't make any different. Is there any setting on the governor or a different hole on the lever that I need to try? Really puzzled here.
#2
M
mechanic mark
M
mechanic mark
enter your serial number in order to locate service manual & wiring schematic for your mower.
https://www.ariens.com/en-us/manuals/download
scroll down page for manuals, enter 992071 model number & 350700 serial number.
https://www.ariens.com/en-us/manuals/download
scroll down page for manuals, enter 992071 model number & 350700 serial number.
#3
C
c5vettster
The serial number for the engine is 3507009331. The tractor is 000612. Do you think that engine model needs more than just 12V on the carb and ignition box? Thanks
C
c5vettster
enter your serial number in order to locate service manual & wiring schematic for your mower.
The serial number for the engine is 3507009331. The tractor is 000612. Do you think that engine model needs more than just 12V on the carb and ignition box? Thanks
#4
C
c5vettster
Thanks! It looks like the manual for the tractor.
I don't understand why the new engine only runs at half the RPM. Is there anything special about wiring the ignition on this kohler engine? It has 12V on the box. I left white and yellow wires hanging. It runs, but only at half rpm and appears to runs too rich. It is almost as thought it only fires the spark plugs every other cycle.
C
c5vettster
enter your serial number in order to locate service manual & wiring schematic for your mower.
https://www.ariens.com/en-us/manuals/download
scroll down page for manuals, enter 992071 model number & 350700 serial number.
Thanks! It looks like the manual for the tractor.
I don't understand why the new engine only runs at half the RPM. Is there anything special about wiring the ignition on this kohler engine? It has 12V on the box. I left white and yellow wires hanging. It runs, but only at half rpm and appears to runs too rich. It is almost as thought it only fires the spark plugs every other cycle.
#5
C
c5vettster
C
c5vettster
A very odd thing. I took the muffler off to make sure I have no obstruction. The muffler was clear. However, when I run it w/o the muffler, only the left cylinder was firing - I could see the blue flame out of the exhaust port. The other cylinder was dispensing un-burned fuel fix. Naturally I took the spark plug out of that cylinder thinking that the engine would stop. However, after a moments hesitation, the other cylinder started to fire. I used an ignition tester and on one and then on the other cylinder and both were showing robust spark. I think I have an ignition problem whereby there is a lack of synchronized ignition between two cylinders.
#6
PTmowerMech
Have you tried pulling the governor rod to see if it idles higher? if it idles up, then it could need adjusting.
PTmowerMech
I am repowering Gravely Z 252 mower model 992071. It originally came with a 27hp CV740 and I found a NOS replacement that is exact with exception of newer ignition module. The new engine is CV740-0020. The older engine is CV740-011. I had to come up with a new wiring harness. The carburetor + ignition box are now powered from a tractor pin that was marked for carburetor but was previously unused. The other engine carb was wired to the regulator line + the starter wire. I think I wired everything correctly. The engine starts easily and shuts down with the key. However, it doesn't go up in RPM. I've check and both the throttle and choke are wide open. The limiter screw appears to have no effect so to speak. But the engine only goes up to ~2500 RMP at WOT. I can't figure out where my problems are. Do you think the voltage on the ignition box maybe unstable? I tried wiriting it directly to the positive terminal and it didn't make any different. Is there any setting on the governor or a different hole on the lever that I need to try? Really puzzled here.
Have you tried pulling the governor rod to see if it idles higher? if it idles up, then it could need adjusting.
#7
tom3
tom3
Swap spark plugs, see if the dead cylinder goes with the plug. Does the engine have two coils? If two coils maybe swap coils and see. Or one single coil with two wires to the plugs? If one single the timing would have to be ok if the other cylinder is running right.
#8
B
bertsmobile1
B
bertsmobile1
Pull off both kill wires and see if it suddenly works properly.
If this is the case the diode between the two coils to prevent them talking to each other has failed
If this is the case the diode between the two coils to prevent them talking to each other has failed
#9
C
c5vettster
I just took the mower to the kohler dealer for warranty repair. I think something is wrong with the ignition system. It has that digital ignition setup and there is a TSB on how to convert it to regular two-coil setup. They pickup the mower today. I will keep you posted on the progress.
C
c5vettster
Pull off both kill wires and see if it suddenly works properly.
If this is the case the diode between the two coils to prevent them talking to each other has failed
I just took the mower to the kohler dealer for warranty repair. I think something is wrong with the ignition system. It has that digital ignition setup and there is a TSB on how to convert it to regular two-coil setup. They pickup the mower today. I will keep you posted on the progress.
#10
C
c5vettster
The shop has called. They are puzzled as well. Their idea is that the engine has a damaged crankshaft causing timing issues with the valve train. Kohler has authorized them to install a new crankshaft. This really sucks. It seems like I will be down for another 2-3 weeks. I wish kohler would authorize the engine replacement since it reflects poorly on their quality control - a brand new engine with a broken crankshaft.
C
c5vettster
I just took the mower to the kohler dealer for warranty repair. I think something is wrong with the ignition system. It has that digital ignition setup and there is a TSB on how to convert it to regular two-coil setup. They pickup the mower today. I will keep you posted on the progress.
The shop has called. They are puzzled as well. Their idea is that the engine has a damaged crankshaft causing timing issues with the valve train. Kohler has authorized them to install a new crankshaft. This really sucks. It seems like I will be down for another 2-3 weeks. I wish kohler would authorize the engine replacement since it reflects poorly on their quality control - a brand new engine with a broken crankshaft.
#11
C
c5vettster
C
c5vettster
The final update. The shop contacted Kohler and they authorized a full engine replacement. So here is the lesson of the story - even new engines could be fatally flawed from the factor. I am so glad for the warranty.
#12
Scrubcadet10
Scrubcadet10
Good deal.
Same engine as the old one or do you know?
Same engine as the old one or do you know?
#13
C
c5vettster
Kohler sent the dealer a new long-block, so the plastic and all the accessories are from the old new engine. Overall I am pleased with Kohler warranty, albeit it would be nicer if they QC-ed their engines before shipping them from the factory.
C
c5vettster
Good deal.
Same engine as the old one or do you know?
Kohler sent the dealer a new long-block, so the plastic and all the accessories are from the old new engine. Overall I am pleased with Kohler warranty, albeit it would be nicer if they QC-ed their engines before shipping them from the factory.
#14
PTmowerMech
When I was an inspector at Trane, I inspected 1 out of ever 6 cranks that came to my station. If one was bad, I'd check the ones before, until I got to a good one. And check all those after it, until I got to a good one. If I had to have checked every crank that came down the line, I'd have to check about 4,500 per day. There was just not enough time in the day for that.
You may have gotten a monday morning or a friday afternoon engine.
PTmowerMech
Kohler sent the dealer a new long-block, so the plastic and all the accessories are from the old new engine. Overall I am pleased with Kohler warranty, albeit it would be nicer if they QC-ed their engines before shipping them from the factory.
When I was an inspector at Trane, I inspected 1 out of ever 6 cranks that came to my station. If one was bad, I'd check the ones before, until I got to a good one. And check all those after it, until I got to a good one. If I had to have checked every crank that came down the line, I'd have to check about 4,500 per day. There was just not enough time in the day for that.
You may have gotten a monday morning or a friday afternoon engine.
#15
C
c5vettster
Yep. I've glanced on the costs of the work - the total invoice came to over $2K, including $600 in labor. Kohler must have lost a lot of money on this lemon.
C
c5vettster
When I was an inspector at Trane, I inspected 1 out of ever 6 cranks that came to my station. If one was bad, I'd check the ones before, until I got to a good one. And check all those after it, until I got to a good one. If I had to have checked every crank that came down the line, I'd have to check about 4,500 per day. There was just not enough time in the day for that.
You may have gotten a monday morning or a friday afternoon engine.
Yep. I've glanced on the costs of the work - the total invoice came to over $2K, including $600 in labor. Kohler must have lost a lot of money on this lemon.
#16
B
bertsmobile1
B
bertsmobile1
If they inspected each & every part properly then you would be paying air graft type prices for engines & engine parts.
So a sample of every part is tested and a sample of every engine off the line is tested.
Some tests that are very quick are done on every unit.
When i was in QC we used a math calculation called Certaincy tables to work out how many had to be tested.
And to give you some idea, the factories in China that have no QC will have around a 20% failure rate.
A riding college works at an importer who brings in stuff foe big box stores.
They have to honour warranty and usually over order 20% to cover warranty claims.
What ever is left over after warranty has expired is then sold as "defective" at auction generally as a single lot.
For for instance would go to a batch of metal. pull a single ingot from some where in the load , and that could be 10,000 ingots.
That one got tested and if it was not dead on center of speck, they rejected the entire batch so we had to remelt the whole lot.
So a sample of every part is tested and a sample of every engine off the line is tested.
Some tests that are very quick are done on every unit.
When i was in QC we used a math calculation called Certaincy tables to work out how many had to be tested.
And to give you some idea, the factories in China that have no QC will have around a 20% failure rate.
A riding college works at an importer who brings in stuff foe big box stores.
They have to honour warranty and usually over order 20% to cover warranty claims.
What ever is left over after warranty has expired is then sold as "defective" at auction generally as a single lot.
For for instance would go to a batch of metal. pull a single ingot from some where in the load , and that could be 10,000 ingots.
That one got tested and if it was not dead on center of speck, they rejected the entire batch so we had to remelt the whole lot.
#17
C
c5vettster
I don't know. I would think that given that these engines are their "commercial line" they should test everyone of them using propane. Honda tests each of their generators that way.
C
c5vettster
If they inspected each & every part properly then you would be paying air graft type prices for engines & engine parts.
So a sample of every part is tested and a sample of every engine off the line is tested.
Some tests that are very quick are done on every unit.
When i was in QC we used a math calculation called Certaincy tables to work out how many had to be tested.
And to give you some idea, the factories in China that have no QC will have around a 20% failure rate.
A riding college works at an importer who brings in stuff foe big box stores.
They have to honour warranty and usually over order 20% to cover warranty claims.
What ever is left over after warranty has expired is then sold as "defective" at auction generally as a single lot.
For for instance would go to a batch of metal. pull a single ingot from some where in the load , and that could be 10,000 ingots.
That one got tested and if it was not dead on center of speck, they rejected the entire batch so we had to remelt the whole lot.
I don't know. I would think that given that these engines are their "commercial line" they should test everyone of them using propane. Honda tests each of their generators that way.
#18
B
bertsmobile1
Which is why Honda re the most expensive engines.
You may have noticed that Honda no longer make riding mower engines.
Why ?
Because they would not cheapen their engines to a price point that the mower companies were willing to pay.
The mower companies are in a similar boat because to produce a quality mower they would exceed the price that the public is willing to pay.
The mower buying public en mass are totally stupid when it comes to assesing a ride on mower so what is the cheapest or prettiest will outsell all others
There is a tipping point between volume & price and if you get on the wrong side of it your business is headed for bankruptcy.
If you want a top quality mower that will work flawlessly from the day you buy it and will have a very long service life then you have to pay for it.
However most will happily buy a new $ 1000 ride on every few years than spend $ 10,000 on a mower that will last 20 + years, it is as simple as that.
As a larger & larger section of the population works outside of the manufacturing sector the ability of people to understand the economics of manufacturing anything rapidly decreases to the point that most have less than no idea why things cost what they do.
Then there is the peverse idology that advertisers have instilled into the population that you need it, you need it now and the price has to be within your reach for no other reason than you need it.
Thus the market produces what the customer is willing to pay for.
B
bertsmobile1
I don't know. I would think that given that these engines are their "commercial line" they should test everyone of them using propane. Honda tests each of their generators that way.
Which is why Honda re the most expensive engines.
You may have noticed that Honda no longer make riding mower engines.
Why ?
Because they would not cheapen their engines to a price point that the mower companies were willing to pay.
The mower companies are in a similar boat because to produce a quality mower they would exceed the price that the public is willing to pay.
The mower buying public en mass are totally stupid when it comes to assesing a ride on mower so what is the cheapest or prettiest will outsell all others
There is a tipping point between volume & price and if you get on the wrong side of it your business is headed for bankruptcy.
If you want a top quality mower that will work flawlessly from the day you buy it and will have a very long service life then you have to pay for it.
However most will happily buy a new $ 1000 ride on every few years than spend $ 10,000 on a mower that will last 20 + years, it is as simple as that.
As a larger & larger section of the population works outside of the manufacturing sector the ability of people to understand the economics of manufacturing anything rapidly decreases to the point that most have less than no idea why things cost what they do.
Then there is the peverse idology that advertisers have instilled into the population that you need it, you need it now and the price has to be within your reach for no other reason than you need it.
Thus the market produces what the customer is willing to pay for.
#19
PTmowerMech
Getting a 5 yr old mower without several things wrong with it, is rare. The engines are usually in ok shape. (usually) but almost everything MTD makes is gonna need bearings, belts and pulley's.
PTmowerMech
Which is why Honda re the most expensive engines.
You may have noticed that Honda no longer make riding mower engines.
Why ?
Because they would not cheapen their engines to a price point that the mower companies were willing to pay.
The mower companies are in a similar boat because to produce a quality mower they would exceed the price that the public is willing to pay.
The mower buying public en mass are totally stupid when it comes to assesing a ride on mower so what is the cheapest or prettiest will outsell all others
There is a tipping point between volume & price and if you get on the wrong side of it your business is headed for bankruptcy.
If you want a top quality mower that will work flawlessly from the day you buy it and will have a very long service life then you have to pay for it.
However most will happily buy a new $ 1000 ride on every few years than spend $ 10,000 on a mower that will last 20 + years, it is as simple as that.
As a larger & larger section of the population works outside of the manufacturing sector the ability of people to understand the economics of manufacturing anything rapidly decreases to the point that most have less than no idea why things cost what they do.
Then there is the peverse idology that advertisers have instilled into the population that you need it, you need it now and the price has to be within your reach for no other reason than you need it.
Thus the market produces what the customer is willing to pay for.
Getting a 5 yr old mower without several things wrong with it, is rare. The engines are usually in ok shape. (usually) but almost everything MTD makes is gonna need bearings, belts and pulley's.
#20
B
bertsmobile1
B
bertsmobile1
Quite true
But
Bearings, belts and pulleys are wear items, just like tyres on your car.
They should be replaced as a matter of course every X or Y years.
My commercial customers generally drop their mowers in near the end of the season and get a full service.
This includes new spindle bearings and every second year, new idler pulleys & belts ( if the belt has lasted that long ).
As most say, an extra $ 300 once a year is nothing compared to breaking down on site and paying a full crew for sitting on their butts while he organizes repairs or even worse having to mow several acres with push mowers .
Then rescheduling the work that had to be missed, paying weekend penalty rates or overtime rates to catch up, etc etc etc
Great Dane recommended new spindle bearings every year and they are big bearings
But
Bearings, belts and pulleys are wear items, just like tyres on your car.
They should be replaced as a matter of course every X or Y years.
My commercial customers generally drop their mowers in near the end of the season and get a full service.
This includes new spindle bearings and every second year, new idler pulleys & belts ( if the belt has lasted that long ).
As most say, an extra $ 300 once a year is nothing compared to breaking down on site and paying a full crew for sitting on their butts while he organizes repairs or even worse having to mow several acres with push mowers .
Then rescheduling the work that had to be missed, paying weekend penalty rates or overtime rates to catch up, etc etc etc
Great Dane recommended new spindle bearings every year and they are big bearings