Wisconsin Robin Wi-185

[slomo]

When you remove the oil dipstick the oil slinger will spray oil and air out the tube. (assuming a splash lube motor) Compression is probably ok. What oil are you using the engine?

I've never opened the oil stick when running till I did this one. I've seen engines like the Intek's, that is one trick to find a blown head gasket. I'm running Wallys World Supertech 30w in all my mowers. This is a splasher engine.

slomo

 

[tom3]

One thing I've seen that is weird. The cooling fins of the motor get jammed up with grass etc and the motor starts running hot. Cylinder distorts at the head bolts. If it runs for a while like that you'll see a wear pattern showing right beside the bolt holes on the cylinder walls. Might be hard to see but worth a look.

 

[slomo]

Yes, it is iron sleeve.
Sounds like the bottom ring is not wiping the oil off the cyl wall or perhaps the drain holes from that ring are all clogged.
If I were u, i would remove the piston and clean the piston and replace the rings. I mean it is 30ish years old....
While you are at it, rent the cylinder bore gauge from Autozone or the like and measure it while it is open to see if the cyl is out of round.
Gasket wise, i used silicone gasket when i opened mine up, and you can always make a gasket for the cylinder head if yours falls apart.

Yup, bottom ring is slacking on the job. Head gasket came off in one piece undamaged. It was a metallic shim looking gasket. Guess this winter I will open her up and do some ring and piston groove cleaning. Hoping the rings are simply stuck with carbon and cleaning will restore them. Bore is pristine. Like you said, drain holes in the piston are probably clogged.

slomo

 

[slomo]

One thing I've seen that is weird. The cooling fins of the motor get jammed up with grass etc and the motor starts running hot. Cylinder distorts at the head bolts. If it runs for a while like that you'll see a wear pattern showing right beside the bolt holes on the cylinder walls. Might be hard to see but worth a look.

Cooling fins now, are clean. Can't attest to the 4 decades of previous usage. I will do another bore inspection this winter.

slomo

 

[slomo]

One thing to add is this engine sounds like it has a rod knock. That or the muffler has gone in super performance mode?? Wondering with the head off, can I slowly rotate the engine and watch piston movement to see if there is a rod issue? Like flywheel turns but piston doesn't say in a 1 degree movement then piston moves as normal? Might not be able to see something in the thousands of an inch of excess slop with the naked eye. Obviously better to measure the little guy.

slomo

 

[upupandaway]

One thing to add is this engine sounds like it has a rod knock.

R u sure it is rod knock u hear? You can find out if it is piston slap you hear while u have it open, push right and left side and look if the piston rocks when u do it. If slap is from the crank journal, i guess you could gently turn the crank a hair back and forth while the piston is at middle position to see if there is play\clicking before u open up the block...

 

[slomo]

R u sure it is rod knock u hear? You can find out if it is piston slap you hear while u have it open, push right and left side and look if the piston rocks when u do it. If slap is from the crank journal, i guess you could gently turn the crank a hair back and forth while the piston is at middle position to see if there is play\clicking before u open up the block...

I can move the piston side to side in the bore with my finger. Guessing this is a forged piston normally running a wider bore gap?? Or it's 40 years old and worn. I can see what looks like the piston doesn't sit proper in the bore center maybe??

Think the rod is okay. Seems to be directly attached to the piston meaning I can't "see" any movement other than the piston going up and down as normal.

Found a block of grass/dirt on the very bottom of the cooling fins. There is a metal air directing plate/shroud that goes around the block. Blob was stuck in there where I couldn't see it. Maybe 1.5" wide x 1". All clear and open now.

There is a tiny hole in the center of the piston. Doesn't seem to go all the way through. I can insert a small screwdriver tip in it.

slomo

 

[slomo]

I've got the engine bore near vertical now. Sprayed WD-40 (solvent) a couple times. Carb cleaner, this garage door lube that says it removes stuck items, Diesel and now ATF. Will keep soaking the rings in effort to loosen them up. Most likely they will need to be removed from the piston and cleaned up.

Noticed with this soaking the fluid gets by the rings now. Does take a few minutes to lower the level in the bore. Depends on how thick the solvent was. Maybe a week or more worth of soaking will help?

slomo

 

[slomo]

Thinking about heating the outer piston face circumference to loosen the rings. Fill the cylinder back up with solvents. Donnyboy heated the rings directly.

slomo

 

[tom3]

Usually with a sleeved bore the piston is cast aluminum with no coating or treatment. Sounds like lots of standard wear in that motor. And the trend has been to use short skirt pistons in later years which leads to piston slap pretty early in the motor's life.