Motorcycle Repair: Honda trail 55 engine question, crankcase pressure, pushrod engine

Question
Hi Bill,

Well I finally got my Honda trail 55 running after a 35 year hibernation and actually it runs pretty well though I notice once it warms up it doesn't run as well as when cold and it begins leaking oil out of the dipstick/fill cap as if pressure is building in the crankcase...does this sound like there is a vent plugged someplace and if so what would be a good tip for cleaning said vent?  many thanks

Jeff

Answer
Jeff, These funny little engines are unique in that they don't have oil pumps! The rods are splash fed and the camshaft has a groove in it that turns and feeds oil to the top end a little at a time.

There should be a vent on the top of the crankcase, but you probably can't get to it unless you remove the motor, as I recall. Try replacing the O-ring on the dipstick first.

If the rings are stuck/sticking from sitting for the past 35 years, you may experience some excessive smoke and crankcase pressure. If this doesn't subside with some running in time, then you may have to pull the head and cylinder and freshen up the piston and rings. Pretty easy to do with a horizontal pushrod engine.

Adjust the valve clearances to .002" cold and check to see that the points are opening at the F mark alignment on the flywheel. Compression should be about 100 psi.

Be sure that the fuel system is totally clean and that all carburetor passages are clear and jets are not blocked.

Bill Silver