low compression one side only

[gkevin]

have an LT180 with the fh500v twin kawasaki. It will crank and run ok but one side of the exhaust would go super hot (like glowing in daylight hot) while the other one is unusually cool. so i took the exhaust apart. no blockages - all good. while i had the exhaust off, i started it again. one side i cant get my hand near it. the other is so cool (while running) i can keep my hand under it for minutes. moving on, I adjusted the valves back to spec.

then i checked compression. one side 115 (cool exhaust) - the other 57 (thermonuclear exhaust). I pulled the heads, took the valves out and checked them for straight and seats. dirty but good. cleaned it all up. no broken or bent parts. put it all back together with brand new cylinder gaskets torqued to spec. exact same readings. I can add a little oil to the cylinder and get maybe 3 extra lbs compression but it doesn't change like worn rings.

my next two guesses are a worn cylinder (although i checked it when i had the head off and it looked good with no ridge at the top) or a flat cam. I guess it could also still be seats/valves. is there something else I should check? how would you recommend I check and in what order?

Thanks for any help. i'm just getting into small engines and dont know what I dont know...

Kevin

 

[7394]

I would check for an intake leak on the hot side, running lean can make it run real hot.

When you check a cylinder bore, I find it is best to check the bore in 3 different places with proper I.D. mics.

Leak down test will pin point the area, either top (sounds like) or bottom.

 

[motoman]

Glowing red...is an exhaust hooked up that could be clogged? That kind of heat has probably softened your cylinder head beyond use on that side imo, sorry to say.

 

[lwalper]

Intake leak? Running lean? Maybe??

57# compression - not caused by an intake leak. Could have been precipitated by an intake leak/running lean/overheat problem. Could also be a warped/cracked head (from heat) or gasket.

Flat cam? Maybe, but probably not. Take the valve covers off. If you can see the valves going up and down, probably not. Are the valves properly adjusted? (0.003 - 0.005" valve lash) Does yours have an automatic compression release?

There's a service manual for the fh500v at encoreequipment.com/wordpress/wp-content/uploads/2012/06/17hp_FH500V1.pdf

 

[bertsmobile1]

Intake leak? Running lean? Maybe??

57# compression - not caused by an intake leak. Could have been precipitated by an intake leak/running lean/overheat problem. Could also be a warped/cracked head (from heat) or gasket.

Flat cam? Maybe, but probably not. Take the valve covers off. If you can see the valves going up and down, probably not. Are the valves properly adjusted? (0.003 - 0.005" valve lash) Does yours have an automatic compression release?

There's a service manual for the fh500v at encoreequipment.com/wordpress/wp-content/uploads/2012/06/17hp_FH500V1.pdf

TAKE YOUR COMPRESSION TESTER AND PUT IT SOMEWHERE THAT GIVES YOU THE MOST PLEASURE AND LEAST NUTRITIONAL BENEFIT>
mowe engines have a decompression mechanism so compression readings are less than useless forget about them, ignore tham, do not take any more of them erase the numbers from your mind they have no significance .
Am I getting through ?
If you really want to check your cylinder, do a leak down test not a compression test.

One side stone cold, the other side stinking hot

1) remove the wire that goes inbetween the two coils , it has a diode in it and is prone to failure which causes timing problems.
2) spray around the hot cylinders intake with WD 40 etc FROM A TRIGGER PACK - NOT A SPRAY CAN.
If you get white smoke from the exhaust or the engine changes speeds you have an air leak
3) remover the carb, clean out the jets.
Hook it up to the fuel line then blow through the venturi with low pressure air and you should see a stream of atomised fuel coming out the engine side ( it will of course go bang if an ignition source is nearby so some care needed )
4) finally read the manual because when every thing fail then you check the manual.:laughing:

 

[willys55]

TAKE YOUR COMPRESSION TESTER AND PUT IT SOMEWHERE THAT GIVES YOU THE MOST PLEASURE AND LEAST NUTRITIONAL BENEFIT>
mowe engines have a decompression mechanism so compression readings are less than useless forget about them, ignore tham, do not take any more of them erase the numbers from your mind they have no significance .
Am I getting through ?
If you really want to check your cylinder, do a leak down test not a compression test.

One side stone cold, the other side stinking hot

1) remove the wire that goes inbetween the two coils , it has a diode in it and is prone to failure which causes timing problems.
2) spray around the hot cylinders intake with WD 40 etc FROM A TRIGGER PACK - NOT A SPRAY CAN.
If you get white smoke from the exhaust or the engine changes speeds you have an air leak
3) remover the carb, clean out the jets.
Hook it up to the fuel line then blow through the venturi with low pressure air and you should see a stream of atomised fuel coming out the engine side ( it will of course go bang if an ignition source is nearby so some care needed )
4) finally read the manual because when every thing fail then you check the manual.:laughing:

Spot on!!!!