did that and the cold side got hot and the side was warm not why would this happen
briggs and stratton 25hp valve cover not heating up evenly
- Thread starter ACF
- Start date
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
Hammermechanicman
Lawn Addict
- Joined
- Jan 10, 2020
- Threads
- 65
- Messages
- 3,832
Run engine under a load for an hour or so and then pull the plugs and compare. Then Go from there.
Shane4u200
Forum Newbie
- Joined
- Apr 5, 2021
- Threads
- 1
- Messages
- 3
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.
Cajun power
Active Member
- Joined
- Apr 11, 2023
- Threads
- 1
- Messages
- 86
this^
Cajun power
Active Member
- Joined
- Apr 11, 2023
- Threads
- 1
- Messages
- 86
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!
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
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
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