A10 plunger timing side pressure

[Drew Back]

I noticed an air leak coming out of the rear upper part of my timing cover oil pressure seems good returns really fast to tank could this be a crank case breather problem?? The bike runs very nice..

[duTch]

 Drew, I've half an idea what you mean, but I think you need to slow down and regroup...??  If there is an air leak, I'd expect there to also be an oil leak.
 Maybe post a photo with some arrows and circles...

 Not what I said for starters, I changed it

[Drew Back]

Ok here is the pic a lot of air coming out to the right side of the blue tape

[Topdad]

Hi Drew , the mag pinion is just there as you well know spinning and displacing whatever air is in there so could it just be a poorly fitting timing side cover/gasket ?

[TT John]

Hello Drew.

I had exactly the same problem, found that after removing the head and checking the pistons in the bore that I had a lot of play, tried to cure it with a new set of rings but still the same plus oil spewing out from the left cylinder, coming up past the rings, so the only thing was to have a rebore & new pistons. Not fitted yet but will let you know the outcome next week when I reassemble.
BTW, I had fantastic compression and the bike ran really well but once that oil starts going past the piston you realise that you have to take bold steps.

Regards  TT John

[RichardL]

I have to admit, I don't understand how TTJohn's problem correlates with Drew's problem. Regarding pressure in the case, in looking at the timed breather (some years ago), it appeard to me that breathing occured 90 degrees ATDC. It also seemed to me that it's main purpose was to have a fairly neutral pressure in the crankcase so oil could be pumped in and sucked out.  Regarless, I believe some pressure or vacuum inside the crankcase is normal.

Drew, your timing cover appears to be severely cracked and I'm wondering if it's not due to someone in the past trying to screw down the non-tach cover while a tach driving bolt was in place on the mag pinion. This could easily lead to a cracked and distorted cover that not only leaks from the crack but also from the gasket joint.

Richard L.

Edit1: On another look, maybe the crack occurred due to the impact that caused the deep scuff near the top of the cover.

Edit2: Yeah, yeah, yeah, I missed the point that TTJohn's bad rings and pistons meant a lot of blow-by and excess crankcase pressure. Also, I understand how pistons working against pressure is not good for power, but if oil can't get in, pistons won't be working at all.

Edit3: Hey, I just realized, plunger breather operation is different from swingarm, isn't it?

[muskrat]

G'day Drew.
Could it be coming from the plugged hole in the inner cover? Check the breather is pegged to the cam pinion and the cork is good (compresses 1/2mm when cover is fitted.

Richard : The "cracks" are etchings/art work. Breathers are the same plunger/swingarm.
Cheers

[duTch]

 Can't see any oil leak - I think you may just need a new gasket...

Edit3: Hey, I just realized, plunger breather operation is different from swingarm, isn't it?

 Musky got in first

[Drew Back]

Thank you all for the great input it is coming out about where the auto advance would be turning I will check to see if my 58 does the same thing..
Richard the cover is old school acid etched with stars I will take a better pic for ya...

[RichardL]

The "cracks" are etchings/art work. Breathers are the same plunger/swingarm.
Cheers

YES! Now I see that. I seem to have gone off the deep end. Hmm? Never known that to happen before. 

Richard L.

[Drew Back]

Here is that pic Richard I think its quite a cool cover someone put a lot of time in it..