Sticky Exhaust Valve - How To Fix It???

[leeave96 496]

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) 12,221]

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 272]

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 7,207]

... 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 2,696]

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) 2,299]

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 496]

Lots of great suggestions - thanks!

 

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

[dbartlett1958 99]

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 1,580]

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 486]

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

[Fordiesel69 272]

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 7,207]

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 605]

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 37,259]

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.

[HankB 22]

Good morning Gents (for some definition of good.)

 

Edit: Solved. I pulled the head and was dismayed to find a couple bolts little more than finger tight. The gasket itself had deteriorated near the exhaust valve and the filler between the outer metal layers had blown out in that area. Of note, this gasket did not have the ring around the inner edge of the gasket that would prevent this. Takeaway: No cheap gaskets and this one (and the other in the package) will go back to the jungle river. I reused the old gasket and will order another to have on hand.

 

I came by this post because I have a performance issue on a 1985 312-8 with a Kohler K301 (of course.)

 

I was mowing and it was running great. Then It lost RPMs and I suspected it was out of gas (though when I've run out of gas in the past, it would just stop Right Now.) I disengaged the mowing deck and RPNs picked right up so I drove a hundred feet so I wouldn't have to lug the gas can out to the mower. (I'm nothing if not lazy.) I shut the throttle and RPMs came down and it just stalled instead of idling. When I went to add fuel, I saw that there was still probably 1/2 to 1/4 tank still there. After fueling, it would crank but not start. Occasional it would pop through the exhaust. It also seems like it was cranking faster, like it had less compression. I suspected either an ignition problem and while searching for diagnostic tips, came upon a stuck exhaust valve. I've got points and condenser inbound and will run a compression check and probably pull the head today.

 

Any collected wisdom you'd care to share will be most welcome.

 

There's a lot more back story here. The previous time I mowed, I had trouble getting the engine up to speed after starting and it lacked power and that was right off the bat, not after it got hot. I performed the following service:

 

• R&I carb and spray with carb cleaner and blow out jets and passages.
• R&I head and replace head gasket, noting:
• No evidence of leakage past the head gasket.
• Evidence of blow by on piston top opposite exhaust valve.
• Cross hatch in the cylinder still visible.
• More carbon deposits than I like to see, but ont excessive. Likely due to running rich due to dirty air filter.
• Checked valve clearance - both within spec and no adjustment needed.
• Inspected valve seats and valves as much as possible w/out removing valves. No problems seen.
• Replaced air filter (and oiled the new foam.)
• Replaced the spark plug.

Once back together, it started right up and ran great! For about half an hour.  I'm starting to wonder if I disturbed some of the carbon under the head and it is now sitting between exhaust valve and seat resulting on lost compression. Or perhaps I disturbed something in the fuel line that's gotten lodged in the carb. I tend to think not because I poured a little fuel on the air filter which should be enough to get it to run for at least a few seconds and it just popped through the exhaust. That's why I'm going there.

 

best,

 

Edited yesterday at 05:32 PM by HankB

[953 nut 65,839]

@HankB, you are today's winner of the "Lazarus Award" for having resurrected the the oldest post of the day.                          

[HankB 22]

I'm trying to think of the best reply and the things that come to mind:

 

• Some things never get old!
• These tractors are still running and the information is still relevant, no?
• Thanks for noticing!
• The day is still young. 

 

Does the Lazarus award entitle me to anything? 

 

best,

 

Edited 18 hours ago by HankB

[peter lena 9,871]

@leeave96 looks like a simple  trial  , these engines are known for  varnish  deposits  , basically a  reheated / cooled glue , tried  rislone  zinc  zddp  supplement , add  4 0z to 2 qts of oil , bottle specs , also drop carb bowl , clean out ,  get a seperate gallon of  fresh gas , heavily treated with  carb cleaner , hook tis up to your carb , run this in easily / time on it , so heat and cleaners can start to work . don,t scream  the hell out of it and expect a miracle , would also  clean out your  gas tank , think about related , broken down fuel hoses , ad  sta bil  fuel storage  to all my gas , been doing this for years with absolutely  , no  problems . ideas I refer to . have been my  elimination  of  issue . bet its engine oil varnish , hanging up that valve function , my stuff  , starts  up , easily  with  no effort .. have 3 of them that  start and run the same way . just  my  view  to  long eliminated , issue , pete  

[HankB 22]

Hi Pete and thanks for the tips. This turned out to be the result of a (too) cheap head gasket. It lacked the edge protection found on better quality gaskets and resulted in the material sandwiched between the two metal layers to blow completely out. I put the original head gasket back in and the tractor started Right Up and had full power. (I have a better Stens head gasket inbound should this one start to have issued.)

 

I completed the service by changing engine and trans-axle oil.

 

best,