Sticky Exhaust Valve - How To Fix It???

[leeave96 488]

I've got a Kohler K-301 engine and I believe I've got a sticky exhaust valve. The engine get's hot when mowing hard and then sputters and dies. After it cools, the engine will start and run again.

I'm using MMO in the gas, short of that, how do you fix a sticky exhaust valve?

Thanks!

Bill

[gwest_ca-(File Mod) 11,282]

The MMO in the fuel should supply adequate lube to the valve stem. Are you sure the valve lash is not set too tight resulting in the valve not closing when hot?

 

Garry

[Fordiesel69 270]

It is loosing compression?  Probably not the problem, as they usually wear loose instead of tight.  Rule out a coil problem, and a fuel problem first.

 

If you must, the cyl head, carb, and breather need to be removed to access the valve.  Then you compress the spring, remove the keepers and pull the valve straight out.

[Jeff-C175 7,206]

... they usually wear loose instead of tight ...

 

 

With OHV engine I would agree, but with an L-head as the valve face and seat wears, the valve generally 'sinks' further into the engine and tightens the clearance.  The face and seat wear is generally faster and greater than the tappet to cam wear so the tolerance will close rather than open...  just what I've seen from the engines I've had apart...  YMMV

 

A 'lean' fuel mixture can also cause overheating.

[buckrancher 2,694]

sounds like vapor-lock to me check your fuel lines and besure they are away from the block and muffler

[VinsRJ 723]

Are you sure it has spark when it dies? Could be a bad condensor.

[Terry M-(Moderator) 2,206]

Could maybe be a leaky head gasket??   One of my older riders had the same symptoms/problem you are having.   I discovered it taking the heads off to look at the valves.   so I cleaned things up and installed new gaskets, fine tuned the carb and problem solved. I'm guessing the leaky head gasket was causing it to run too lean and hot... I even surprised myself!!

 

although your problem could be something else.

 

just my 2 cents worth

[sorekiwi 761]

The only time I have ever seen a small engine with a stuck valve, has been a result of the engine sitting for a while.  I've never seen one stick during use.

 

I tend to agree with the others - look for something else first, or maybe check your compression both hot and cold.

[BOWTIE 226]

Check for spark when it dies. It sounds like a bad coil or condenser.

 

BOWTIE

[leeave96 488]

Lots of great suggestions - thanks!

 

I'll go through this engine when it happens again to rule out some possible causes.

[dbartlett1958 96]

I had an old Simplicity with a 19-D Briggs that acted that way. After several go rounds with the carb and points, it turned out to be the coil. I added a "Kohler" external coil and a ballast resistor and never looked back.

[WH nut 553]

Are you sure it has spark when it dies? Could be a bad condensor.

I agree with this

[ericj 1,578]

i have a 312-A with a 12M on it that would just loose rpm back fire and come back to life the hotter it was out the worse it would get and if it was cooler it would be okay. finally found a guy who told me it was the exhaust valve hang up. when it would get hot the valve would start to stick. he said wheel horse put out a service bulletin on this. he took it apart and knurled or drilled the valve guide open more. he said that he has seen them so bad that he has had to cut the valve off and take it out in pieces down through the lifter galley. after his repair the tractor runs great now

 

eric j    

[Shuboxlover 479]

When I had a sticky exhaust valve, it wouldn't even run.....I would definitely suspect something electrical!!!

[Fordiesel69 270]

i have a 312-A with a 12M on it that would just loose rpm back fire and come back to life the hotter it was out the worse it would get and if it was cooler it would be okay. finally found a guy who told me it was the exhaust valve hang up. when it would get hot the valve would start to stick. he said wheel horse put out a service bulletin on this. he took it apart and knurled or drilled the valve guide open more. he said that he has seen them so bad that he has had to cut the valve off and take it out in pieces down through the lifter galley. after his repair the tractor runs great now

 

eric j    

 

Never heard of this.....  Does anyone know where to find this bulletin? 

[Jeff-C175 7,206]

However unlikely a sticky exhaust valve may, or may not, be... it shouldn't be ruled out of a proper diagnosis.

 

My point is, a technician should NEVER say NEVER... because it will often make you go around and around in circles.

 

Do ALL the diagnostics and then come to a conclusion about the 'most likely' cause of the problem.

 

A quick search of the 'net will show that sticky exhaust valves are really NOT all that uncommon.  My guess is that the problem STARTS with a LEAKING exhaust valve, so if a valve is sticking, it could well be a SYMPTOM and not the CAUSE.

 

Keep an open mind, don't say it "can't be" just because you've never seen it before.

[Don1977 604]

You didn't say wht model this K301 was on, if it is a older C-Series with gas tank located behing the dash, I could be the fuel pump.

[AMC RULES 37,153]

So...how'd it turn out...any updates yet?   

[kenw520hc 4]

read erics post because he is 100 percent correct. been around small engines and wheel horse over 40 years,the other posts have some good info also, but one trick you an try to see if it is a sticky valve when hot is try changing the oil to 5/30 or 10/30 that was part of kohler and wheel horses fix for a sticky valve when hot. however there are those cases where so much carbon and goo built up on the valve stem the only fix was a valve job. give the oil change a try its a easy fix.