Crank pressure pumping oil out of tach drive?

[Anonymous]

My bike has an intermittent problem where it blows oil out of the tach drive and I was wondering if anybody has found a reason for this. Just to show how intermittent this is I washed my bike about 600 km ago and did not have any problem with the oil blowing out until today after returning from a 300 km ride. With the bike off I could see oil bubbling out around the cable. What's strange is that I opened up the oil filler cap and the oil continued to bubble away. I have a new tach gear, oil seal, and o-ring on order due to wear on the gear's sealing surface but I would like to know if I should do anything else to prevent the problem from coming back. Also, I don't think my oil is boiling but you never know. The cam cover breather is clear and connected properly too.

My friend with an 1166 kit in his 83 has the same problem but it actually pushes his tach cable apart where it crimps to the end.

Steve

[Hap Call]

There are no oil pressure lines going to the tach drive so it can't be the engine oil pressure. It could be the crankcase pressure but if it continues to bubble out for awhile after you've opened the oil fill, that seems unlikely. Have you or your friend seen any leaking around the cam shaft plugs (the rubber half moons at the end of the cams)?

I would pull the tach drive from the head and replace the rubber seal and o-ring. See if that stops it.

Hap

[Anonymous]

I'm with hap, the "O" ring & seal should be the only things in there to let it leak.

[Anonymous]

That's what I figured too but just wanted to make sure that there wasn't anything else amiss. In my case I did buy a new camshaft/tach drive since it had some deep grooves worn into it by the previous seal.

Steve

[earlfor]

Hap is spot on with the solution.

Earl