Oily Spark Plug

[Shorter Grass]

I will take the head off and see what I find

I took the head off and found a notable amount of oil in the cylinder. There is no wear on the cylinder wall and the piston does not have a hole in it and appears to be in reasonably good condition. I am currenlty draining the oil from the mower and have not inspected the oil yet.

Piston rings and bearings - if I am taking the bottom end of the engine apart what all should I replace?

 

[Hammermechanicman]

If you have oil in the cylinder check to make sure there is no gas in the oil. The cover on the side of the engine that covers the valve springs is the crankcase breather. There is a one way valve in it . If this valve sticks closed it can pressurize the crankcase and cause high oil consumption. Change the oil with 30wt run engine till warmed up then turn off and let it sit for a few hours then pull the head. If you have oil in the head pull the carb and check for oil in the intake port. Any oil that might come past the exhaust valve guide will get burned in the muffler.if no oil in the intake port leaves rings and cylinder.

 

[bertsmobile1]

Being a side banger oil can only get into the cylinder 2 ways without major damage
1) past the oil scraper ring
2) down the inlet valve guide

neither will be apparent from the crankcase
After that here is a crack in the cylinder, moving valve guide , hole in piston and via the crankcase breather .
There is also no bearings inside the engine.
All shafts run directly on the castings / forgings
Was the bore really good
Was the cross hatching complete with no bare patches indicating wear ?

 

[Shorter Grass]

Being a side banger oil can only get into the cylinder 2 ways without major damage
1) past the oil scraper ring
2) down the inlet valve guide

neither will be apparent from the crankcase
After that here is a crack in the cylinder, moving valve guide , hole in piston and via the crankcase breather .
There is also no bearings inside the engine.
All shafts run directly on the castings / forgings
Was the bore really good
Was the cross hatching complete with no bare patches indicating wear ?

I will check all of the above.

Where am I looking for the cross hatching?

 

[Shorter Grass]

Where am I looking for the cross hatching?

 

[Scrubcadet10]

This is what crosshatch would look like in the cylinder,

However with it being that model kool-bore, i don't think they honed them from the factory, as i replaced a short block on one awhile ago and it wasn't crosshatched (honed),

 

[Shorter Grass]

This is what crosshatch would look like in the cylinder,

However with it being that model kool-bore, i don't think they honed them from the factory, as i replaced a short block on one awhile ago and it wasn't crosshatched (honed),

The bore of mine has not been honed from the factory so there is no cross hatching?

 

[Scrubcadet10]

Yes, not honed from the factory, no crosshatch.

 

[slomo]

Basic Briggs flathead Kool Bore.. I'd guess the cylinder is shot. New rings might help it but this is getting pretty common these days. The chrome plating on the piston wears and the bare aluminum surfaces rubbing together creates a mess. Hope I'm wrong but you'll have to pull the head and check.

Chrome plating??? Really? I've never seen a piston with chrome plating.

slomo

 

[Shorter Grass]

Chrome plating??? Really? I've never seen a piston with chrome plating.

slomo

The piston in my lawnmower is not chrome plated. The head of the poston is not marked or cracked.

I cannot feel any lip in the cylinder wall. I will remove the piston and check it and the priston rings.

Is it worth fixing if it is the cylinder that is the problem?