Planet Minis

m82a1fella

This engine is driving me nuts! I had this engine assembled at a local shop. This thing has been apart four times now. The cylinder was bored 50 over with a new piston and rings installed. New valves relapped with the exhaust (no seal) guide replaced and honed to specs. New valve guide seal installed. I had the head magnafluxed to check for cracks, checked out ok. All new gaskets and seals installed throughout. My mechanic and I are at a standstill. Has anyone had any problems like this??? Could the head or cylinder be warped?? This engine is about to become a boat anchor! HELP!!!!!!!

LoudFastUgly

You need to check that ring gap has been offset, and that they are installed correctly (very small letter stamped into top of first and second ring, should be 'up' towards head).


You need to check the clearance between the piston and the wall of the cylinder to ensure the bore is correct with respect to the diameter of the piston.

m82a1fella

The rings have been gapped properly as well as the bore to the piston...

m82a1fella

They also have been installed in the upright position. This has been checked twice so far as well as the bore size in relation to the piston.

fatcaaat

Lots of little things that could go wrong for sure. I could think of a few off the top of my head.

1. The cylinder is out of tolerance...bored too much, bored out of round, not honed in correctly
2. The rings not offset good enough, upside down, or you have the chrome and oil ring reversed.
3. Your timing is a tooth or two off
4. Your carburator or air cleaner needs to be cleaned
5. Your spark plug is incorrectly gapped
6. You've got too much oil in it
7. You've got oil getting into the combustion chamber via the head gasket, the intake valve guide, or the exhaust valve guide.
8. Your points are adjusted incorrectly
9. You're trying to run synthetic oil before the rings are properly seated
10. The rings have not properly seated

Think about these...there are more, but one of these is the likely culprit.

50rider340

Id also try putting on a brand new pipe. Its possible that the original pipe is filled up with oil from when it originally smoked. So when the build up in the pipe gets a little warm and then hot it keeps smoking. I had this problem with a pipe i had after a rebuild. This was on a C70 so street crusin. After about 2 weeks of going wide open down the streets it stoped smoking.

m82a1fella

Ok, here is what goes on when I start "the hog" up. Everything runs fine until the engine get to operating temperature. Then it continually smokes very minimally. When you rev the engine up it puffs big time. Then it continues to smoke just a little. But it wont quit smoking. Does any of this weed out any of your probable symptoms? BTW, hows that H motor going??

m82a1fella

I took off the pipe and started the engine with no resolve. It still smoked right out of the exhaust port...

50rider340

i think something wasnt put together right in the head. Clearly oil is passing through something and causing you to burn it. Is the plug really black? Id buy a stock chinese head for cheap. If you want by a stock jug and head from dratv.com if it smokes after putting that all in then id throw the motor out and start from scratch.

fatcaaat

Sounds to me like your bore is out of tolerance. As it heats up, the cylinder gets out of tolerance a bit and allows for oil to go past the rings.

You are supposed to have a .001" clearance on the bore to piston. I bet it is bored out of round or off tolerance. I once had a very similiar problem on a china motor....ran clean until it warmed up and then smoked like crazy. Turns out the clearance was off by .002" I ended up replacing the cylinder from a 56mm to a 57mm and it stopped smoking.

And what FastMC says...is the vent pinched? Take the top valve tappet cover off and see what happens once its warmed up.

FastMC

Is the crankcase venting properly ?
Do either of the valve stems look wet with oil ? (check right away after shutting motor off).
Any signs of oil pathways on the head gasket ? (must look very closely)
Accidently picked up the premix gas jug instead of the straight gas jug ? J/K

mexicanyella

Premix won't make most four-strokes smoke noticeably. I can verify that. Might carbon them up eventually, but not blow a bunch of smoke.

Do you have oil vapor puffing out the crankcase breather hose on the back of the crankcase when you run it, or rev it? If you've got a bunch of blowby at the rings, you should, and this would indicate that something was amiss at the rings/bore area.

Another possibility, indicated by a lack of anything coming out the hose, maybe your breather hose is partially or completely plugged (mud dauber nest, spider egg sacs, other storage-related creature debris) and crankcase pressure is forcing oil up into the combustion space.

A compression test is pretty essential at this point. If your compression is within spec, oil level's right and the breather's working right that pretty much points to valve guide issues; that's the next place oil can get into the intake or exhaust path. If you had oil getting into the combustion chamber from the pressure feed passage, I'd think you'd be talking about a bad head gasket, which ought to show up on a compression test.

Don't throw the motor away, for heaven's sake. You'll figure it out.

LoudFastUgly

Run a compression test and a leak down test.

You could try putting it on the patch or Nicorette, though I've heard cold turkey is best.

dirtbkr188

Corrugated oil ring ends overlapped, not allowing the ring to expand and letting oil get by...?

vegatron75

I would say #6 and #7 on Fatcaat's list.