A lot of oil in magneto chaincase

[Joker_Bones]

Recently assembled G80 bitsa engine, no more than 40 or 50 miles since first started a week or so ago.

I took the magneto chaincase cover off today, there was a lot of oil in the chaincase, enough for a four inch puddle on the shed floor.

I searched the forum and there was a post by Spriddler which talked of camshaft bushes supplied with the scroll cut in wrong direction, pushing the oil into the chaincase not keeping it in the timing chest

This is the bush viewed from the magneto chain side...

IMG_20231002_192712.jpg

The scroll is as a left hand thread, I assume that is the way it should be, but can't quite figure the logic. Any thoughts?

This is viewed from timing chest side.

IMG_20231002_204702.jpg

The bush is flush with the boss it sits in and I have fitted a gasket of thickness to give nil end float to the camshaft. With the face of the cam running flush with face of the bush/boss I am wondering if oil getting into the bush is finding it easier to go past the scroll than return to the timing chest. Any thoughts?

I am thinking of machining a slot across the face of the bush/boss along the orange line to give oil any easy path to stay in the timing chest. Any thoughts?

[56G80S]

I had a similar problem with a slightly loose blanking plug on the inlet part of the outer cover. Removed it, splayed it a very little and refitted with a little loctite adhesive.

Problem solved.

Just a thought.

Johnny B

[SPRIDDLER]

The scroll is as a left hand thread, I assume that is the way it should be, but can't quite figure the logic. Any thoughts?

Yes, that anti-clock scrolling is the correct way round.
Mine was the exhaust cam bush (forward mounted magneto).
Can't offer any other suggestion than perhaps the bush is very worn (the depth of the scrolling seems to eliminate that) or the c/case breather isn't functioning well causing high c/case pressure. If you can fit a length of flexible tube over the breather drip pipe you should be able to suck but not blow through it.
Or as Johnny B mentioned it's the inlet blanking disc that's leaking - from memory there's no scrolling on that one.

[Joker_Bones]

Thanks fellas...
The crankcase breather assembly was taken out and cleaned when I stripped the engine and I did the suck/blow thing when it was reassembled. You can feel the breather puffing away when the engine is running so I'm happy it is breathing okay.
I was confused by your comments about the blanking plug, then it dawned on me... I called it a G80 bitsa engine because it has G80 stamped on the crankcase, but didn't go on to say it has an Ajay timing/magneto chain case with the blanking plug outside of the chain cavity.

IMG_20231006_184321.jpg

I found a photo of a new bush at BOA scrolled the same as mine, anticlockwise as you say.

1_405d2e5f-f475-46fc-9fb1-490d7ab10d87_300x300.jpg

Also as you say, the bush did not appear excessively worn but there may be some peculiarity of wear causing it to allow oil to pass. I guess I could replace it and see.

[SPRIDDLER]

Also as you say, the bush did not appear excessively worn but there may be some peculiarity of wear causing it to allow oil to pass. I guess I could replace it and see.

Maybe measuring the bush i.d. would help. I doubt that the axle is worn.
(From a rather vague memory, I think the scrolling on my correct bush was quite fine and extended continuously along the whole or 75% of the length of the bush. Yours seems to be a coarser 'thread' with just a couple of turns at the end, but that might be just a trick of the photo - or it may be correct and my memory is wrong. I wonder what the current club spares ones are like.......... ).
The WD technical manual gives some data for the G3 which is also relevant to the G80:

Camshaft bushes clearance.JPG