90 harley evo top breather pouring oil

Need a faster answer?
Hi Robert, it's called wet sumpping. Evo's and earlier engines were famous for oil draining out of the oil tank past the oil pump check ball/valve and into the bottom end when left without starting for long period of time (winter storage). When the bike is restarted the piston downstroke creates pressure in the bottom end which is routed back through the gearcase, up the push rod tubes and into the rocker boxes and finally into the air cleaner where unspent fuel particles are recycled back through the carburator and into the combustion chamber. Oil mist and air are seperated by a baffling system in the cam gearcase compartment. Under normal circumstances there is only a couple ounces of oil in the gearcase and bottom end. If the bottom end has a gallon of oil in it, well you get the picture and the mess. Best way to prevent oil eruptus is to drain it before it has a chance to to relocate and take up residence in your bottom end. Enjoy the new season.
Was this answer helpful?
Yes
No
Thank you for your feedback!