Air leak on right side of engine, near spark plug hole?

[akpasta]

Hello,

The other day I noticed my engine sound changed a bit, esp at idle and low rpms. I looked at the right side of my engine, pulled the throttle at idle, and saw smoke blowing out from someplace near the spark plug! I noticed some bubbling around the spark plug, where it meets the engine head. I got off the bike and started blocking certain areas to determine where the smoke is coming from, it does not appear to be coming from the head gasket, it seems to be coming from the area where the spark plug threads in. I bought new spark plugs of course, wondering if maybe somehow the plug crush washer had been squished too far to maintain a seal, but that hasn't solved the problem. I cleaned off the mating surface as well, and nothing seems to be cracked or anything either. I'm kind of stumped, to be perfectly honest. I might mention, I was out of carb cleaner or starter fluid to spray around and try to discover where the leak is coming from, so that would be next on the list.

Can anyone offer some advice?



Thanks,

Andy

[FAST FRED]

Andy, I had this same problem with a CB160 a while back. It seemed to be caused from the plug not being flush with the head when tighted. I fixed it with two new plug washers and tighted to proper torque.

Fast Fred

[G-Man]

Andy

This is apparently a common problem with these engines. The bond breaks down between the aluminum cylinder head and the cast-in steel liner in the combustion chamber. I don't think that there is an easy fix, other than finding a replacement head. :-(

Often worse with a big-bore kit.

G

[akpasta]

Andy

This is apparently a common problem with these engines. The bond breaks down between the aluminum cylinder head and the cast-in steel liner in the combustion chamber. I don't think that there is an easy fix, other than finding a replacement head. :-(

Often worse with a big-bore kit.

G

F****

[mike in idaho]

Sounds like it's leaking around the cast-in "skull", in the head. I've heard of folks using lead or copper sealing washers under the plugs in an attempt to seal the leak. Might be worth a try before you take the head off.

[akpasta]

Sounds like it's leaking around the cast-in "skull", in the head. I've heard of folks using lead or copper sealing washers under the plugs in an attempt to seal the leak. Might be worth a try before you take the head off.

For what it's worth, when I replaced the plugs, the problem seemed to improve for a short time, however, once the engine warmed up, I noticed the leak again.

Where is the "cast-in 'skull'" ? Are the spark plug threads sitting inside a sleeve that's cast into the cylinder head?

[G-Man]

The skull lines the entire combustion chamber in the head. The valve seats are in it and the spark plugs are threaded in the cast steel, hence the term skull.



G