Could be an excess of blowby from worn or broken rings, broken piston, etc.. Are you sure the power is up to par? If not, you could check compression on that cylinder.
Or, do a *cylinder short test to see if that cylinder is actually firing. That much oil in the air filter and no smoke at the pipe?
Normally I would say... Lift the oil cap at idle and fast idle to check blowby there. But, I don't know if it's normal for the VN to spew pressure there when running or not, some engines do, I've not done it on the VN. The rotor could sling some oil (do not try to touch the spinning rotor), which would be normal, but a fair amount of oil/smoke/air that increases with rpm would indicate excess blowby on most engines.
cylinder short test: remove plug wire on the cylinder, rpm should drop...replace wire, rpm should rise. You do this one cyl at a time on, say, a V8, V6 etc. while it's idling.
I've never run a VN on one cylinder either.
But in our case we'd have to pull two wires, better insulate the fingers.
Last edited by Spockster; 06-28-2013 at 11:52 PM.