sticking kohler valves

[2manyrocks]

I've got a Gravely with a 12 hp Kohler magnum that will shut off running after 20 minutes now. It is getting worse. Already replaced the coil. So I think I have a valve that's sticking when the engine heats up.

Also have another Gravely with an 8 hp kohler that I think the valves have rusted in place because I didn't oil it up before storage and my barn has been excessively wet last year. I have good spark, but the engine won't start even with starting fluid so I'm thinking the valves are rusted in place.

How do you go about cleaning up these valves? I guess I have to take the cylinder head off, but can anybody point me to a guide for how to do this job?

 

[oldnslo]

Kohler Engines: Home

they have a section for illustrated parts and also service manuals I believe.

Yes you have to remove the head and usually the carb to access the valve cover. What may be happening is one of the valves has to tight of a clearance and once it gets warm it opens to the point you build compression. Don't run it muck like this or you will potentially burn a valve seat which may or may not be repairable.

Roy

 

[2manyrocks]

Thanks for the warning.

There are some saying that this is really a problem with 10% methanol gas over 30 days old-that it leaves a residue that sticks valves. I have three engines that didn't have problems before, and now I think they have sticking valves. Since one of them has always been stored in a dry shed, maybe it's more fuel related than moisture related.

 

[jdboy4410]

you can check valve adjustment without pulling the head,but you will have to remove the carb to access the cover.engine has to be dead cold,and postion the piston at TDC on compression stroke,check the clearance with a feeler guage and adjust as necessary.it's not the easiest thing to do,but really it's no big deal.as far as fuel,i have heard alot of complaints associated with the ethanol blended fuel.stabil is a good way to combat it.if you have sticking valves though,i wouldn't think it is the fuel causing it.it would be more wear related.i recall a procedure for the old L models for sticking valves,but that was when there was still lead in the fuel.lead would build up sometimes causing the valves to stick,and also carbon.there are products out there now that do a super job decarbing the engine.i would check the valve adjustment first,and then do a good decarb on the engine.the easy method is to remove the intake boot from the air filter and spray it directly into the carb while the engine is running.you want the engine at operating temp to do it.the other method is to remove the spark plug,and spray the decarb solution into the cylinder,let stand over night,and then drain the oil.this method will clean out the ring landings on the piston,the top of the piston,and also clean up the valves too.refill with fresh oil,and start the engine,it's gonna smoke quite a bit for a couple of mins.get it up to operating temp and i would follow it up with the spray while running method too to get the solution around the valve stems themselves.it definitely helps and will restore some lost compression.another thing to add,if you suspect the valves,do a compression check with the engine cold,and once it shuts off,take another compression check and compare the two readings,easy way to test if the valves are indeed too tight.too tight and the compression will drop dramatically,too loose,you wouldn't see a change in compression,but the engine will not run as it can't complete the combustion cycle because the valves aren't opening or not opening enough.

 

[2manyrocks]

Thank you very much. That sounds like what I want to try. Is there a particular decarb product I should get?

Locally, all I found was Seafoam Cleaner spray at the auto parts store and Blaster Lawn Mower Tune Up at TSC.

 

[RichardTX]

If the engine is losing compression when hot it could be a few things.

1 - valves may be coked/rusted up. Coking usually caused by worn valve guides. I like Marvel oil when dealing with rusty valve stems.

2 - overheating and warping the valves from too lean a mixture.

3 - valve lash too tight

4 - bad head gasket

5 - cracked head or block.

I have seen all of these issues at one time of another. The rarer ones are the cracked head/block and bad head gasket.

 

[jdboy4410]

Richard is correct,these are all things to check.you can buy top engine cleaner from any local GM dealer.their new product isn't as good as the old version,but still is very effective.I don't recall the cost of it,not super expensive.another product is Chevron Techron,but I haven't seen it for a long time.it was what GM recommended for clogged injectors.I personally never used it,but there was a service bulletin about it and having good results with it.I always used the GM stuff and it worked great.I generally use a product called Optimizer,however it is not available for over the counter purchase.It just plain works too.I think I may have about half a case left of it.It is in an aerosol can.I spray it directly into the throat of the carb on a hot engine,and then remove the plug and fill the cylinder with it and let it sit over night.does an awesome job.this stuff runs about $15 a can,and worth the money.if you have some carbon build up on the valve seats,it will remove it.

 

[2manyrocks]

Thanks. Got it soaking in seafoam since that's what we have available here since our local GM dealer went belly up.

 

[2manyrocks]

I actually have two engines that I suspect have sticking valves due to dirty gas.

The good news---tried the Seafoam on my Kawasaki engine that I thought had sticking valves and was able to cut the entire yard without the engine quiting.

I got the Gravely running and it ran for a while pretty well. When I heard it start to sputter like it was going to quit, I started spraying a different brand of top end cleaner in the carb. The engine kept running as long as I sprayed cleaner in it.

Bad fuel pump on the Gravely? It's a Kohler M12 that has a mechanical fuel pump. How do you tell when the fuel pump is going bad?

 

[J_J]

To check manual fuel pump pressure.

Pull the plugs, and remove the hose to carb, and crank the engine. You can put your finger over the hose to judge the pressure. Should be around 3 to 7 lbs psi. You can buy 12v low pressure fuel pump from NAPA to replace the manual pumps, probably for less money. . They make many different pressure of the same pump series.

They used to make rebuild kits for the Kohler fuel pumps, but I understand than stopped making them. The new manual fuel pumps are made of plastic.

Check your fuel seat and float adj.