It seems I have a hole in my head

Paul W.

Paul W.

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May 12, 2018
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Doing some carb tuning today and when I started up the bike, I noticed my pant leg pulsating. I put my hand down on the right side, towards the rear of the bike and sure enough, there was air coming from the head. After the usual checks, I found the following pinhole going into the bolt hole. Has anyone ran across anything like this?


It seems I have a hole in my head


It seems I have a hole in my head


It seems I have a hole in my head
 
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Same thing on my Atlas. Same bolt too. Must be a casting flaw. Weeps oil but no compression loss. I just wipe the oil and go on. My guess is it will slowly continue to get bigger. I might look for a fix when I pull the head again.

Scott
 
For a 1966 bike you are lucky if that is the only thing wrong with it, as annoying as it is-you have no choice to get the cylinder head off and get it alloy welded from the inside.
 
Bernhard said:
For a 1966 bike you are lucky if that is the only thing wrong with it, as annoying as it is-you have no choice to get the cylinder head off and get it alloy welded from the inside.
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Really?

How does one weld the inside of a bolt hole??

A proper fix would be to sleeve the bolt hole.

Personally, I’d try cleaning it up on the outside and smear a decent fillet of JB weld / Devcon etc over it. Remove the bolt, lightly oil it and re fit first, so you don’t glue the bolt in place.
 
This is the fun part of purchasing a vintage machine from someone who did half-assed upkeep or none at all. I do have another head to put on it. I’ll do that in the upcoming weeks and send the original in to see if it can be overhauled. Which includes new stud inserts.

From what I read, it is possible to remove the head with the engine in the frame. It doesn’t sound real fun, but it’s do-able.
 
Re; " I put my hand down on the right side, towards the rear of the bike and sure enough, there was air coming from the head."

You can only be 100 % sure it’s not coming from the combustion chamber if you do a compression check- if it definitely not from there, you may be able to do a temporary repair if you remove the bolt clean hole up with a Dremel and small cutting tool to clean all the oil up as well as roughing it out, leaving no trace of oil, the patch it with one of the alloy pastes on the market. But it might not be heat resistance.
 
those bolts are 5/16 or may be the PO drilled the hole and put 3/8 for a Cdo later barrel ? if not enough meat to drill a bit larger hole ( to make sure it's clean and no other cracks creeping across!) and either fit a loctited brub screw or JB weld
 
Paul W. said:
This is the fun part of purchasing a vintage machine from someone who did half-assed upkeep or none at all. I do have another head to put on it. I’ll do that in the upcoming weeks and send the original in to see if it can be overhauled. Which includes new stud inserts.

From what I read, it is possible to remove the head with the engine in the frame. It doesn’t sound real fun, but it’s do-able.
Click to expand...

It's a while ago I took the head off my N15 but I seem to remember taking out the rockers and pulling the exhaust pushrods before I could get the head off, a bit of a sweat
 
I talked to a mechanic yesterday at a vintage bike show, and he said he had one apart at his shop doing the same thing. There were no holes into the combustion chamber. They were thinking a porous casting and that it was cranckcase pressure leaking out through the threads.
 
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