I seem to have developed a major oil leak coming from the crank shaft. However when I opened the chain cover I noticed that the cush drive was very loose,in fact it was almost falling off. My question is does this have anything to do with the oil leak? The cush drive sets up against a bushing that I can turn. When everything is tighted up I assume that this bushing will no longer turn. Could this be the cause of the oil leak? The shop manuals really don`t address this and I really can`t find a picture of this bushing anywhere. I know I must be missing something. I have Henks CD by the way.
Help! I don`t want to preform major surgery but its a bad leak.

Rick

The cush drive nuts can come undone if not correctly tightened and locked ( I use Loctite on mine). Usually resulting in a lot of clattering before losing drive all together. However I can't really see that it would create an oil leak through the main bearings.(I could be wrong) Any oil escaping through the main bearings will end up in the chain case. Maybe your engine has wet sumped, creating excessive oil in the crankcase, or a blocked breather??

email (option): ronpier@talk21.com

I would agree with Rons assessment..A loose shock absorber assembly would have no effect with regards to creating an oil leak in that area. The cause of your problem lies elsewhere...Ian

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

Thanks for the replies,
I am going to check the three breathers. It very well could be wet sumped now because I haven`t started it since fall. I will pull the drain and see how much oil is in the crankcase,how much should I expect? It has been doing this for a while so wet sumping is not the whole story. The chain case gasket was in bad shape when I took the case off so that might be why so much oil was on the ground. Doesn`t look good though,sounds like it needs a rebuild.

While its all lose take the drive sprocket off & look at that inner primary case joint, check that the cush nut hasn't been unscrewed enough to contact inside the outer cover thereby pushing away & distorting the inner cases joint (where it bolts to the crankcase) that could open up a small gap to let oil out. Hopefully its that & you can just get the Cush nice & tight, drain the sump & go riding.

I have the chain case off. I can see oil dripping out of the crank bushing. I drained the oil and got about a quart out of the crank case. Is this normal? The washer between the chain case and crank case was in bad shape. Should I make a new one out of leather or go with a more modern material?

Hi Rick..It appears your main problem (and it is not uncommon) is that the oil has drained into the crankcase while the bike has been standing..Once it gets to the level of the main bearings it will leak out past them. The M20 is a dry sump engine so under normal circumstances there would be very little oil in the crankcase. The return side of the oil pump has a larger pumping capacity than the feed side so the cases remain pretty much empty under normal use.
It is worth fitting a new ball and spring to the timing cover anti drain valve and reseating the ball into the casing to prevent, or at least very much reduce this problem...There is another anti drain valve in the base plate of the oil pump which may also be worth looking at if doing the timing cover valve doesn't improve things...
It is best to make the crankcase/ primary cover gasket from material that is not too thick or soft..If that is done the three bolts that hold the inner primary cover on tend to distort the cover, squashing it into the gasket. Use some normal engine gasket material about .030"-.040" thick and apply some silicone sealant when fitting the inner cover and gasket to the engine.The heads of the three bolts should be cross drilled so that they can be wired together with some light locking wire after tightening. Also, don't go too mad tightening them..it isn't difficult to damage the threads in the crankcase...Ian

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

Thanks Ian,
That helps alot. I was hoping it wasn`t a bearing going bad. I still wonder why the bike never smoked when I started it but... The information on the gasket is most helpful I would have used something too thick. I will also just plan on getting a new ball and spring for the timing cover. Also thanks for the advise on tightening the cross drilled bolts.
Thanks again,
Rick

Hi Rick..Your unlikely to ever have a main bearing problem with an M20..the bottom half of the engine is very robustly constructed and well lubricated and if properly built and maintained it is a trouble free high mileage unit.
In 40 years I've seen worn bearings but never one that has completely failed..and in that time I have personally never had a big end failure either..though I've seen a few in customers engines. It's usually lack of oil changes or insufficient oil that has caused the problem.
You can get a new ball and spring for the anti drain valve from C&D Autos for a couple of quid...fitting details are in the factory worksheets....Ian

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