Small Oil Leak

craig2148 · Post by **craig2148** » Tue Nov 25, 2014 3:51 pm

I have a small and mysterious oil leak on my CB77 that I can't trace. The front facing surface of the left spark plug and cap get a bit of oil on them after a ride. I have to wipe oil film off the front surface of the left side cover as well. My guess is the cam cover with the tach drive is leaking since I can't see what else it would be. The bike doesn't smoke, plugs are dry and tan and there is no air leak at the plug itself, so it's not coming from the combustion chamber. I don't see an oil trail anywhere either. What doesn't make sense is that if the cam cover was leaking I'd expect to see oil all over the spark plug cap, not contained in a small area near the bottom surface. Any ideas?

Thanks.

48lesco · Post by **48lesco** » Tue Nov 25, 2014 4:25 pm

Might be from the tach cable connection to the head cover. I haven't been into one of those in a while, but I remember there being a couple of paths for oil to make it out around that joint. There was a little rubber washer seal in the tach cable that needed to be in good shape and an o-ring under the threaded part that accepts the cable.

- or -

It may not be that at all... Sometimes 305's seep oil at the spark plug hole where the steel combustion chamber penetrates the aluminum casting. That's a well-documented issue, and was the topic of a Honda service bulletin. A quick search of this site turned up the post below, and it's also in Bill Silver's engine rebuild guide.

http://www.honda305.com/forums/cb77-oil ... 396-7.html

craig2148 · Post by **craig2148** » Tue Nov 25, 2014 4:38 pm

Thank you 48lesco. The tack cable is new and all seals are intact. After reading the link that you attached I believe the "separation" is the issue. Mine would fall into the first category of a minor mess that needs frequent cleaning.

Your response is greatly appreciated.

48lesco · Post by **48lesco** » Tue Nov 25, 2014 10:33 pm

Well thanks, and I wipe a little off after each ride too. Part of the experience.
-48

mcconnellfrance · Post by **mcconnellfrance** » Tue Aug 04, 2015 12:20 pm

Hi, I have discovered this thread after looking for information about oil leakage from the tachometer drive on the left cylinder head on my 1964 CB77. I have replaced the O ring part number 91301-268-020 between the tacho gear bushing and the cylinder head cover. I have still got a small leak.

I saw in this thread from 48lesco that says the tacho cable should have a small rubber seal.

"............There was a little rubber washer seal in the tach cable that needed to be in good shape and an o-ring under the threaded part that accepts the cable."

I don't see this rubber washer seal on my tacho cable. Any one have information of what this looks like or a part no? (I suspect that it comes as part of the cable assembly).

Regards,
Gordon