LK3504 Breather Smoke

[LopeyZ]

I found a steal of a deal on an LK3504 about a month ago. It had a locked motor with Great Bend loader for $1000. Figured I can't go wrong and hoped for stuck piston over seized crank. Turned out piston was rusted in the cylinder. I freed it up but that cylinder had no compression... stuck rings. Ended up pulling all pistons, honed cylinders, freed up rings and slapped it back together. Had already invested another grand in head work and parts so didn't want to dump more in new rings... they are stupid expensive comparatively speaking. Anyway, it runs well now but noticed some positive crank case pressure and smoke at 1000 rpm. Run it a bit and check again at 2000 rpm... no smoke and very little pressure. I thought blow by got worse at higher rpm. Does anybody else have a little breather smoke at idle? There is no exhaust smoke at all.

 

[xcgreene]

Depending on the piston, there can be gas ports that direct pressure behind the compression rings, effectively seating the ring against the cylinder more tightly at higher speeds. Also, depending on the crankcase and crankshaft style, more oil will be thrown onto the cylinder walls at higher speeds, allowing for a tighter compression seal. The oil pump may also be a bit worn, it may produce sufficient oil pressure while at higher speeds, but a bit low at idle, not allowing quite enough pressure for the jets that need to squirt oil up to the cylinder walls to help with compression and cooling. Their are a lot of different engines out their, with many different ways of lubrication, but some of these methods may explain your situation.