Hi all went to start the M20 today after it has been sitting for a while. As it had not been started for about 3 months I undid the drain plug in the bottom of the crankcase and drained out the oil that had found its way into the crankcase. Bike started ok, after about 2 minutes of idling in the garage oil started to coming out of the breather and before long a had a pool of oil about 5” diameter on the floor. I have had oil coming out of the breather if I have not drained the oil from the crankcase before starting the engine. I don’t understand why the oil is coming out of the breather when I drained the oil from the crankcase before starting the bike. Any help would be appreciated.
Cheers Mark

It's the same as when you drain a car to change the oil, you get alot more out quicker if the engine & oil is hot.
Your cold oil would've clung to all the surfaces (all the crankcase components add up to a huge surface area) particularly if you had turned the engine over a few times before draining.
when your engine heated up the oil thinned & was blown out, a small amount of hot oil can make a big puddle.

Hi cycle Fred,
Thanks for you for your advice. I tried again this time I drained the crankcase for about 1 hour before trying to start the engine. I drained about 125 ml of oil from the crankcase, this was quite a lot as it had only been standing overnight. Started the bike and after about 2 minutes I started getting oil coming out of the breather. I continued to run the engine for another 5 minutes as the pool of oil was getting quite large on the floor. I removed the cover plate and brass filter from the bottom of the engine. I noticed that the steel ball in the filter was staying up and not sitting on the bottom of the inlet to the pump. I tried to see if I could move the ball down by using a small screwdriver but no go. I will remove the oil pump next to see if I can find anything that looks out of place. Another other help would be appreciated.
Mark

Hi Mark..The ball in the pump plate is the cause of your problem. This is an anti drain valve as well as an oil pick up. The ball should move freely in its 'tube' and sit at the bottom of the tube when the engine isn't running. It 'seats' in the bottom of the tube and prevents oil leaking from the tank through the oil pump gears to the sump.
The ball is retained in the tube by a small wire clip (above the ball) which has to be removed to get the ball out.
If you get the ball moving and seating correctly and the other anti drain valve in the timing cover is functioning correctly as well, that should solve the problem...Ian

email (option): ian@wright52.plus.com

Hi Ian,
Thank you for your help, I will remove the pump from the engine and give it a good clean and see what I can find.
Cheers,
Mark