Kohler Backfires

[jellyghost 378]

I just changed the oil on my 10hp Kohler in my 1978 C-101.  After running a little while, fire came out the stack.  One minute later, it did it again and died.  What does this indicate?

[Tuneup 1,433]

I vote sticking exhaust valve and it's springtime so time to pull the head and inspect, decarbon, valve clearance, etc. It would allow you to remove the valves if you want to go that far. If it's been a while since you've been in there, it's time, Spring or not.

[jellyghost 378]

I am not the most mechanically inclined, but I have a garage and most tools.  Could you point me towards an instructional video or writeup?

[pfrederi 17,741]

 

[ebinmaine 67,626]

56 minutes ago, jellyghost said:

writeup

That Kohler manual is a great write up. 

 

 

[Mickwhitt 4,642]

Yes  remove the head and see whats happening in the combustion chamber. 

If anything it will show you the overall state of the engine and point you towards any bigger problems. 

[jellyghost 378]

It's my understanding that I need to buy a new gasket before removing the head.  Is that correct?

[Mickwhitt 4,642]

Never re use a head gasket, they are designed to crush down when the head is tightened to torque specifications and so once used you would have to over tighten the head bolts to get a seal. 

You will definitely need a torque wrench to re tighten the head so find one that goes up to the value shown in the service manual. 

There are a few threads on here that cover strip downs and rebuilds,  have a GOOD read of them before starting. To many it is fairly basic mechanics but if you have not had much experience its a job that you can really mess up an engine with if done poorly. We can walk you through it but a certain amount of savvy is still required, what if a head bolt snaps? If you are at all not confident you can handle the job find a service centre or engine shop that can do the work. 

Mick 

[Mickwhitt 4,642]

This is the removal of a lawn mower cylinder head which should have been straight forward.

Here you see the engine block, cylinder head and gasket laid out.

The combustion chamber with its coating of carbon which needs to be carefully removed. Its only aluminium so nothing too aggressive. 

Here is the face of the cylinder block. I cleaned this before taking the photo. Valves look OK.

But you can see the cylinder head bolt close to the exhaust port has snapped in the block. That's because this bolt is subject to the most heat and so is prone to seize in place. Removing it will be a pain as it will need drilling and tapping out.

The cylinder walls don't look worn or scored, but if you want to check the piston rings we are into a much more involved process.

As we said before the gasket is history after one use so get a new one. 

A simple job on the face of it but taking the head off can be like opening a can of worms. 

[wallfish 17,011]

55 minutes ago, Mickwhitt said:

But you can see the cylinder head bolt close to the exhaust port has snapped in the block.

NOT FUN !

You can weld a nut to the broken bolt but do it CAREFULLY. Cover everything so splatter isn't a problem and don't weld it to the block. The heat should release the threads and you can back it out with wrench or socket. Much easier than drilling it out and in my experience, an Easyout tool is anything but easy. The bolt metal has more torque before it broke.

 

[ranger 1,750]

Having removed more than my fair share of broken bolts/studs in the past, in a situation like this, I would first drill a small hole right through the remains, then place a large diameter washer over the piece. Then, using the welder, weld the washer to the stub. Then place a large nut over the washer and fill the center with weld. The washer stops you ‘accidentally welding the nut to the block, or whatever the bolt is stuck in. Filling the nut with weld applies heat right where you want it, expanding the bolt and hopefully breaking the rust / “Loctite” seal. The idea of the hole is to allow the “hollow” bolt to “expand/contract” inwards, also helping to break the seal.

Perhaps a stud, instead of a bolt would not be a bad idea in this particular location?

Doug.

[ranger 1,750]

1 hour ago, wallfish said:

NOT FUN !

You can weld a nut to the broken bolt but do it CAREFULLY. Cover everything so splatter isn't a problem and don't weld it to the block. The heat should release the threads and you can back it out with wrench or socket. Much easier than drilling it out and in my experience, an Easyout tool is anything but easy. The bolt metal has more torque before it broke.

 

I’ve also never had much luck with “Easyouts”, by the very fact they are tapered means they will tend to ‘expand’ the part you are trying to extract, thus tightening it in the hole! I do have a set of extractors which resemble “Torx” bits. You first drill a hole, then hammer the appropriate size extractor into the hole and unscrew. I have had mixed results with these. I suspect any of these types of extractor are really only meant to be used on fasteners which have failed in service, for whatever reason, and not for fasteners snapped during removal due to rust, etc,? I have seen people using “Torx” bits as extractors, with considerable success, again, only on fasteners which had failed in service! On occasions I have had to completely drill out a broken stud, I have fabricated a drilling jig, picking up from adjacent holes where possible. This I have found to be the only reliable way to ensure minimal damage to original threads present. It also helps greatly if you have access to ‘Left Hand’ drill bits! It takes relatively little time to ‘Cobble’ together a rudimentary drilling jig from scrap compared to the time you could spend trying to repair the damage caused if the drill bit ‘Wanders’, especially if you’re using a hand drill.

Doug.

 

p.s. Thinking about broken head studs, if you have a lathe, you could machine some ‘Top Hat’ bushes, different bores, to fit the cylinder head bolt holes, refit the head, drop a bush into the hole above the broken bolt ( use the largest first to clean up the end of the broken stud to ensure the smaller drills will start ok without wandering). Then drill in successively larger steps.

if you don't have a lathe to make the drilling bushes, you could probably purchase bushes/sleeves in the size you need from bearing suppliers, etc.

Edited April 17, 2021 by ranger

[pfrederi 17,741]

15 minutes ago, ranger said:

I’ve also never had much luck with “Easyouts”, by the very fact they are tapered means they will tend to ‘expand’ the part you are trying to extract, thus tightening it in the hole! I do have a set of extractors which resemble “Torx” bits. You first drill a hole, then hammer the appropriate size extractor into the hole and unscrew. I have had mixed results with these. I suspect any of these types of extractor are really only meant to be used on fasteners which have failed in service, for whatever reason, and not for fasteners snapped during removal due to rust, etc,? I have seen people using “Torx” bits as extractors, with considerable success, again, only on fasteners which had failed in service! On occasions I have had to completely drill out a broken stud, I have fabricated a drilling jig, picking up from adjacent holes where possible. This I have found to be the only reliable way to ensure minimal damage to original threads present. It also helps greatly if you have access to ‘Left Hand’ drill bits! It takes relatively little time to ‘Cobble’ together a rudimentary drilling jig from scrap compared to the time you could spend trying to repair the damage caused if the drill bit ‘Wanders’, especially if you’re using a hand drill.

Doug.

 

 

This Rigid set uses the "Torx" looking extractor.  They have worked for me sometimes but not all....

 

[ranger 1,750]

Nice set!