Kohler Command CV491S dumping fuel out exhaust

[mikenj]

I'm hoping someone here may be able to help with a problem I'm having with this engine. Engine has about ~ 170 hours on it and about 8-10 yrs old.

The problem I'm having right now is when I try to start the engine the carb throat fills up with gas and fuel comes out the muffler. I also noticed gas being spit back through the carb, but not with enough force to blow up. I've had a long history with repairs on the engine, but for a while it did run fine. Here's the repair history roughly in this order from what I can recall:

* Replaced flywheel key (was sheared when I bought it)
* Cleaned and checked carb since mower sat for a while
* Mower ran fine for a while before stopping. However, the valve train (lifters) were noisy for a while and went away when warm)
* After running for several hours across several days, it stopped. Engine started dumping fuel out exhaust
* Took carb apart again, cleaned and checked bowl for gas and height (again) Needle valve appeared fine.
* Did compression check, OK given ACR on these engines. Did a leak down test and did notice air leakage through both valves and crankcase at TDC.
* Checked, cleaned and lapped valves. Installed new head gasket. I did note that clearance between rockers and valve stems was practically non-existent. Not sure if this is normal (engine has hydraulic lifters)
* At some point the engine wound up shearing another flywheel key. I have not cut any grass with the mower so nothing was hit.
* Mower sat 3-4 months before trying to start yesterday.

What I *think* might be wrong is either the ACR sticking, hydraulic lifter problems or some other carb issue. I'm not sure what to do next....

[Lawnranger]

Sounds like the needle & seat are not stopping the flow of gasoline through the carburetor or the float could be sunk/sticking. I had a case where the needle w/rubber tipped seat looked fine but as soon as I replaced it the flooding stopped so this could be your problem as well.

[mikenj]

Sounds like the needle & seat are not stopping the flow of gasoline through the carburetor or the float could be sunk/sticking. I had a case where the needle w/rubber tipped seat looked fine but as soon as I replaced it the flooding stopped so this could be your problem as well.

Good idea, the engine does have a fuel pump so I guess it's possible the pressure is overcoming the seal on the needle. I'll have to give this a shot and hookup a gravity feed to see if it stops flooding. Thanks for the tip!

I still do have noisy lifter problems so I also thought I had valve problems with the spitting back in the carb.

[Lawnranger]

Sounds like the needle & seat are not stopping the flow of gasoline through the carburetor or the float could be sunk/sticking. I had a case where the needle w/rubber tipped seat looked fine but as soon as I replaced it the flooding stopped so this could be your problem as well.

Good idea, the engine does have a fuel pump so I guess it's possible the pressure is overcoming the seal on the needle. I'll have to give this a shot and hookup a gravity feed to see if it stops flooding. Thanks for the tip!

I still do have noisy lifter problems so I also thought I had valve problems with the spitting back in the carb.

The noisy lifter problem is secondary to a leaking fuel problem which is a major safety issue that needs to be addressed before attempting to start the engine. Fix that fuel leak and then tackle the other issues.

[mikenj]

The noisy lifter problem is secondary to a leaking fuel problem which is a major safety issue that needs to be addressed before attempting to start the engine. Fix that fuel leak and then tackle the other issues.

I was thinking I could toast some marshmallows right from my exhaust first. haha... kidding of course and definitely is a major safety issue. Probably will get a chance to look again this weekend so I'll post back with findings.

[Mr-Moe]

[quote][At some point the engine wound up shearing another flywheel key. I have not cut any grass with the mower so nothing was hit./quote]

Flywheel needs to be lapped to shaft, then torqued to proper torque.
There's a lot of mass in that flywheel and if you don't have a good fit between the crankshaft and the flywheel [lapping the two]
then you will get some slipage between them [sheared key].

Moe

[mikenj]

[At some point the engine wound up shearing another flywheel key. I have not cut any grass with the mower so nothing was hit./quote]

Flywheel needs to be lapped to shaft, then torqued to proper torque.
There's a lot of mass in that flywheel and if you don't have a good fit between the crankshaft and the flywheel [lapping the two]
then you will get some slipage between them [sheared key].

Moe

Good call, the keys are actually made of steel, which surprised me at first but I wouldn't want to drop that flywheel on my foot

How do you lap the flywheel to the crank? From what I recall it was a good fit and I torqued it down.

[Mr-Moe]

Remove key from shaft, put some lapping compount on flywheel end of crank.
Gently put flywheel onto shaft and spin around. Back anf forth in both direction.
Remove flywheel, clean both shaft and flywheel of a compound.

This method will match up the tappers on shaft to flywheel and made for a good fit.

[TORK]

To fix the noisy lifters, try putting a little Seafoam in the oil. Should only take a capful or two. Sometime the lifters will stick and clatter, the seafoam will help clean them out.

[mikenj]

To fix the noisy lifters, try putting a little Seafoam in the oil. Should only take a capful or two. Sometime the lifters will stick and clatter, the seafoam will help clean them out.

Awesome, thanks for the tip! I'll do that and run for a while before I change the oil again. I'm pretty sure I used 10W-30 but I'll make sure this time around.