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have a b/s model 44t977-0023-g1 on a john deere Z535m, using old school to check coil firing i placed my hand on valve cover one side got hot fast but the other did not heat up, so i suspected that coil was bad so replaced coil no change, checked valve clearance was off a little so adjusted did not result in any change to valve cover heating up my spark tester shows that we have spark and engine does run any one have a clue why there is no heat on one side of engine.

thanks

The exhaust side will be hot but not the intake - Never really checked valve cover temps on any engine, On large industrial engines if you felt the intake was hot it told me I had a burnt valve

Could be the hot side is running leaner than the cold side. Try this old school test. Remove the shroud so you have access to the intake manifold. Start engine and spray the intake manifold and gasket areas with carb cleaner around the hotter side. What you are looking for is any change in RPMs while doing this. If you see a change that area is sucking in air creating a lean mixture. Patience and a good ear are your friends.

Can be either the plug is shorted or you could have dropped a push rod.

Well it wouldn't be running if he dropped a push rod or a valve

Twins run just fine on one cylinder until you put it under a load

I second that. Matter of fact I just got through checking out a Kawasaki FXT00V engine that was just dying engaging the deck. Dropped the exhaust valve push rod. Of course I will going in as the exhaust valve is sticking after parts get here.

I even seen a couple that only struggled to get the deck up to speed while running on one cylinder.

To add to the above
Several customers have come in finally for a service because their mower has no balls & bogs down in heavy grass.
They tell me it has been like that from new
A quick inspection shows they are running on 1 cylinder and from the conversations it seems that they were like that from new ( no dealer pre-delivery & no initial service )
In almost every case on pushrod is either chewed up in the sump or just sitting there not connected
It is very common
and on B & S V twins a faulty kill wire that makes one side fire at the wrong time is also quite common.

Rivets said:

Could be the hot side is running leaner than the cold side. Try this old school test. Remove the shroud so you have access to the intake manifold. Start engine and spray the intake manifold and gasket areas with carb cleaner around the hotter side. What you are looking for is any change in RPMs while doing this. If you see a change that area is sucking in air creating a lean mixture. Patience and a good ear are your friends.

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did this there was no change in rpm, buddy suggested that muffler was clogged on that side due to color difference on exhaust piping what do you think

Pull the plug wire off the cylinder that gets hot and start it and see if the other side heats up.

Hammermechanicman said:

Pull the plug wire off the cylinder that gets hot and start it and see if the other side heats up.

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did that and the cold side got hot and the side was warm not why would this happen

Hammermechanicman said:

Pull the plug wire off the cylinder that gets hot and start it and see if the other side heats up.

Click to expand...

pulled plug wire and the side would not get hot got hot so what would cause this to happen what are the repairs to fix

Run engine under a load for an hour or so and then pull the plugs and compare. Then Go from there.

Check for spark on both plugs, if only getting spark on one of them try pulling the kill wire off both coils and check for spark again. If you have spark on both with kill wires removed, you probably have a bad kill wire with bad diodes. You can pick up a new kill wire with diodes on Amazon, should be pretty cheap to buy. Just a suggestion.

Rivets said:

Could be the hot side is running leaner than the cold side. Try this old school test. Remove the shroud so you have access to the intake manifold. Start engine and spray the intake manifold and gasket areas with carb cleaner around the hotter side. What you are looking for is any change in RPMs while doing this. If you see a change that area is sucking in air creating a lean mixture. Patience and a good ear are your friends.

Click to expand...

this^

I had a similar problem...one side running very hot and the other cooler. Also some surging.

it ended up being two things, related:

intake manifold gasket was toast and allowing air into one cylinder - causing a lean condition (too much air in the ratio...causing overheating)

but what caused the intake manifold gasket to blow?

both head cylinder gaskets were blown!

but what causes the head cylinder gaskets to blow?

mowing in a triple digits and getting caught in a hard cold rain....caused the head cylinders to cool rapidly and develop gasket blow by. The hard cold rain event might have also caused the intake manifold to contract rapidly also and develop a gasket leak...

or it may have been the other way around...intake gasket leaks, lean condition...very hot engine cycle THEN the head cylinder gaskets fail.

but the two definitely were related as the problems happened in the same time line.....all pointing to a high engine heat cycle and contracting rapidly from a hard cold rain. never had this happen before. But then these last two summers in south louisiana has put quite a strain on my mowers. Very hot...and droughty...and then all of sudden the clouds dump cold rain with little warning. (emphasizing to never mow in the rain on a very hot day! and also never to wash a hot engine with water !)

I chased this problem and made all the mistakes throwing parts at it.

* props to RIVETS for the tip on how to test a intake manifold leak with the carb cleaner...it's an easy thing to do and if there is a leak...you will notice a RPM change with this method. I would just add, let the engine warm up in to high heat cycle...sometimes the intake manifold gasket leak does not fully develop until the engine gets at top heat cycle. the trick is to make sure you are not spraying carb cleaner near the carburetor filter box! only at the specific area of the intake manifold where it mates to the head cylinder. And of course FIRE HAZARD WARNING! Be careful when you do this. Don't put your face and hands into the vapor. that never ends well if things go south. A fire extinguisher is a good idea and also before doing this make sure you are in an open area, and there are NO FUEL LEAKS or any combustible liquids or materials nearby!

I feel that Bert and Shane are on the right path. There is a black wire attached to each of the two coils. Each wire goes through its own diode on its way to the key switch to find a ground in the off position to stop the engine. Understand that a good diode will only allow currant one way. In the on position if one of the diodes was to go bad as in a burn out no contact that cylinder would continue to run in the off position but also if the diode was bad allowing current in both direction the two cylinder can see each other and the wire with the bad diode will seek a ground in the other coils kill wire. I have seen both ways happen.

I looked at your engine parts list and see that it is using a Nikki Dual throat 2 barrel carb.
Setting in the drivers seat looking forward you need to determine which cylinder is dead, right or left. (you did not say which in your description?
You say you have fire to both plugs and the valves are adjusted properly to .005 AND ASSUMING THAT BOTH CYLINDERS HAVE COMPRESSION , at least 80lbs.
Remove the air filter cover and the air filter and look down into the carb throat openings.
You will see a left and a right. They intake are isolated from each other, hint if one side of the carb clogs that cylinder is dead, no fuel.
After you determine which cylinder is dead get a small oil or squirt can for priming the throat that is dead. You are going to give the dead side of the carb a small prime of gas while the engine is idling or running just above idle and if the engine momentarily hits on that cylinder that side of the carb is bad.
This works sometimes to clear the carb but may require removing the carb for a good cleaning later. (this procedure save lots of times and will quite often make it run ok.
Once you determine its the carb, you can then remove the engine air shroud and you will see a triangle shaped 3 SCREWS plate on top of the Nikki dual throat carb carb. Remove the 3 screws and gently peck on the plate and try to lift it without ruining the gasket, but no sweat if the gasket tears it easily made, it's just a flat gasket. If the old gasket comes off ok just wet it with engine oil or vaseline to soften for re-use.
You need to wear safety glasses and take low pressure air of about 25-35 lbs and blow into the channels that are now exposed, but do not direct inject air pressure. Gas will be blowing up and out two of the vent holes towards your face coming from the bowl and there are also little jet passages that are being cleared.
Re-install the plate and prime the engine and test run for 15 seconds with the air shroud still off. If still dead cylinder due to carb, the carb will need removed and re-built or replaced. If it runs ok install a new fuel filter in the fuel pump fuel supply hose..
Go to this link and look at Briggs & Stratton v-twin Nikki carb part 1 and part two and look at picture #11 in part two about the top plate and the jets and vents. (IF YOU DETERMINE IT'S THE CARB when you do the prime run test)
Let us know if you determine it's the carb and We can send you some rebuild links for the different types of Briggs Nikkis if you need to go into the carb. You can also find some you tube links about this type carb removal/re-install. (one size does not fit all here for re-building/repairing/replacing)
https://outdoorpowerinfo.com/repairs/#id_nikki

Report???????????

Hammermechanicman said:

Run engine under a load for an hour or so and then pull the plugs and compare. Then Go from there.

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ran mower pulled plugs left side the one not connected no sign of any fire, right side one that did not get hot had signs of normal use

Forest#2 said:

Report???????????

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side that was not getting had pressure of 150 psi set valves at .005

Just to confirm:
Are all of these confirmed?????
You say it appears the left cylinder is running cold and not producing power when you pull the spark plug wire? (I usually just slide the rubber plugs boot back and ground the spark plug wire tips with a insulated handle screwdriver)
You have changed the magneto and you also see spark at the spark plug?
You compared the right cylinder compression to the left side as close to the same????
You swapped the spark plugs or installed a new spark plug and still no power on the left side?
THE ENGINE DIES WHEN YOU PULL THE RIGHT SIDE SPARK PLUG WIRE?
You adjusted the valve lash per specs?

A IR thermometer is really handy for comparing cylinder balance by reading the exhaust temps of each cylinder. The weak cylinder will usually be colder as compared to the good cylinders on a small gasoline engine.

If the above are confirmed try adding little bit of fuel as suggested in post 18.

ust to confirm:

Forest#2 said:

Are all of these confirmed?????
You say it appears the left cylinder is running cold and not producing power when you pull the spark plug wire? (I usually just slide the rubber plugs boot back and ground the spark plug wire tips with a insulated handle screwdriver)
You have changed the magneto and you also see spark at the spark plug?
You compared the right cylinder compression to the left side as close to the same????
You swapped the spark plugs or installed a new spark plug and still no power on the left side?
THE ENGINE DIES WHEN YOU PULL THE RIGHT SIDE SPARK PLUG WIRE?
You adjusted the valve lash per specs?

A IR thermometer is really handy for comparing cylinder balance by reading the exhaust temps of each cylinder. The weak cylinder will usually be colder as compared to the good cylinders on a small gasoline engine.

If the above are confirmed try adding little bit of fuel as suggested in post 18.

Click to expand...

sitting on the mower the compression on left side is130 psi hot side on the right side cold side it is 135 psi. mower has spark on both coils, with ground connected or not connected. mower starts with ground wire disconnected and will stop when key switch is turned off.
when throttle is increased the engine starts surging/hunting with both coils connected
with the left side plug wire disconnected the right side will heat up.
tried the spray of intake connection no change in rpm
did just do a check of ground wire and ground wire coming from the right side cold side has a connection or maybe diaode that has a protective coating on it and from both ends of this coating there small beads of rubber/plastic coming from it could this be the diaode, and with the melted rubber it be bad causing problems

Yes the kill wire wiring harness on the twin OHV's has blocking diodes in EACH magneto wire. If one DIODE is shorted the ignition will be upset.

First see if the engine will start with the right side plug wire off?

Another test is remove the air shroud and disconnect both kill wires at the MAGNETOS. Be aware if you start the engine with both kill wires disconnected you will have to pull plug wires to kill the engine. (choking will not always kill the engine)
Do not test run the engine over 15 seconds with the air shroud off or it WILL OVERHEAT.

Forest#2 said:

Yes the kill wire wiring harness on the twin OHV's has blocking diodes in EACH magneto wire. If one DIODE is shorted the ignition will be upset.

First see if the engine will start with the right side plug wire off?

Another test is remove the air shroud and disconnect both kill wires at the MAGNETOS. Be aware if you start the engine with both kill wires disconnected you will have to pull plug wires to kill the engine. (choking will not always kill the engine)
Do not test run the engine over 15 seconds with the air shroud off or it WILL OVERHEAT.

Click to expand...

Forest#2 said:

Yes the kill wire wiring harness on the twin OHV's has blocking diodes in EACH magneto wire. If one DIODE is shorted the ignition will be upset.

First see if the engine will start with the right side plug wire off?

Another test is remove the air shroud and disconnect both kill wires at the MAGNETOS. Be aware if you start the engine with both kill wires disconnected you will have to pull plug wires to kill the engine. (choking will not always kill the engine)
Do not test run the engine over 15 seconds with the air shroud off or it WILL OVERHEAT.

Click to expand...

engine will start with right side plug wire removed
engine will start and stop using key with both kill wires disconnected

You say:
engine will start and stop using key with both kill wires disconnected

Wow. It's possessed!!!!!!!!!!!!!!

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ACF said:

engine will start with right side plug wire removed
engine will start and stop using key with both kill wires disconnected

Click to expand...

Fuel afterfire solenoid.

I overlooked the after fire solenoid for turning the fuel supply on off)

Did the engine run smooth with both kill wires disconnected from the Mags?

Or did you detect any change at all?

Forest#2 said:

I overlooked the after fire solenoid for turning the fuel supply on off)

Did the engine run smooth with both kill wires disconnected from the Mags?

Or did you detect any change at all?

Click to expand...

replaed the wiring harness and there was not any change the left side valve cover got hot and right side was just warm rechecked the valve clearance and they are within specs, not sure what to do now totally lost

changed the coils around placed the one on the right to the left side and the one on left to the right side. started both valves covers heated up but did have surging when throttle pushed passed half way point but when under load there is no surging,

B & S Coils should not be handed ( Honda coils are ) but if one of them was originally fitted upside down then it would not fire at the correc time ( if at all 0 due to the way that the Hall Effect Trigger works
So both coils should be fitted the same way round with the kill lead tab facing the cylinder .
FWIW
If flipped the induced voltage will be 180 deg out of phase
On B & S magnetron coils the voltage in the coil goes from 0 - peak negative - 0 - peak positive - 0
When the chip sees negative X µV it fires the coil
If the coil is on upside down it goes 0 - peak positive - 0 - peak negative - 0 so the spark will happen ( or try to happen ) just after the magnets have passed the laminations rather than as the magnets are passing the laminations.
So at best you will get a very weak retarded spark or at worst , no spark at all .

and as bert says they can be installed upside down.
If you look very close and carefully at the black plastic some are labeled in weak small letters, this side up.

You say it surges slightly at mid and upper throttle W/O a load on the engine
If it smooths out under load it will probably be ok.
Might add a fuel additive such as Seafoam to the gas as a carb cleaner.

Sometimes if the rig has a manual choke you can give it just little bitty bit of choke little at a time and correct a light surge due to the carb running little lean and a gas carb cleaner additive might eventually clear such.
In my post #18 you will see tips how I've cleared up a rough running Nikki carb sometimes W/O have to remove the carb by removing the 3 screw top plate.

Sometimes (if all else is correct) a governor static adjust is on the edge of not quite correct, but some of them Intek OHV twins governors do not ADJUST correctly by the book so best to try and live with it as is for now probably. (they can be tricky (trial and error method) to adjust sometimes)