Blow by or bad valve guide?

Jethro · Post by **Jethro** » Sat Apr 03, 2010 9:33 am

I was riding my ca77 pretty hard yesterday down a pass near my home. When I arrived I noticed the tip of the right muffler was a bit moist. Aside from disassembly and using the old micrometer, is there any way of differentiating the issue as a valve guide or ring blow by?

Goodysnap · Post by **Goodysnap** » Sat Apr 03, 2010 1:52 pm

Running a dry and wet compression test is a good way to pick out how much compression loss you have by the rings. If the numbers are off ( especially on the side your having troubles on) in may point you in the right direction. Are you certain its oil? not fuel. I'd tend to think if you had oil coming out the exhaust youd done fouled the plug by then.

LOUD MOUSE · Post by **LOUD MOUSE** » Sat Apr 03, 2010 3:01 pm

Some questions.
Did it run good?
Can ya ride it again without doing anything?
Do ya want to work on it?. .................lm

Jethro wrote:I was riding my ca77 pretty hard yesterday down a pass near my home. When I arrived I noticed the tip of the right muffler was a bit moist. Aside from disassembly and using the old micrometer, is there any way of differentiating the issue as a valve guide or ring blow by?

Jethro · Post by **Jethro** » Sun Apr 04, 2010 11:59 am

Well it is definitely oil and it starts and runs very well. Im quite certain that I would be able to start it and run it with out any problems. Since I have had the bike it has made a strange noise that sounds like a sort of clicking sound. I did the screwdriver sound test and its coming from the head on the right side. I've done other overhauls and I am planning on doing the work on this one as well. I guess I'd better go get busy with it. Thanks loud mouse and goodysnap. Any other input would be awesome!

Jethro

block · Post by **block** » Thu Apr 15, 2010 11:47 am

I am having the same trouble. A fair amount of oil it seems coming out the exhaust on the right side of my CB77. I have a fair amount of white some coming out of the cylinders exhaust and will ruin the plug on that side in a matter of 10 of 15 miles. Does this sound familiar? I had a dry compression of about 120 I believe the other day. Guess I should do a wet...

Jethro · Post by **Jethro** » Fri Apr 16, 2010 1:20 am

Your situation seems a bit more severe than mine. My plug on that right side is not fouling and I have noticed that I only have a wet exhaust when I have the engine running at high rpm. Also my breather is dripping quite a bit of oil.
So I think the dripping breather tube combined with the wet exhaust pipe are evidence of excessive ring blow by.

rustywrench · Post by **rustywrench** » Fri Apr 16, 2010 9:08 am

Jethro,
I'm going to throw my two cents into this just to add some food for thought.
In my rudimentary mechanical mind, I'm thinking that ring blow by would indeed allow oil into the combustion chamber thus fouling the plug. If the plug is not fouling, and wet oil is present in the pipe, that would suggest to me that an exhaust valve guide is allowing oil into the exhaust side of the valve and not the combustion chamber. Unfortunately I don't have a lot of experience with "these" heads so I can't say how to deal with these types of problems, but I can say that will change with time.
My hope is that a more experienced mind can step to the plate and share a thought or two since I have experienced these conditions as well. The gauntlet has been thrown.
RW

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Blow by or bad valve guide?

Blow by or bad valve guide?

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