By Jakub
New purchase, beginning of the learning curve. I’ve notice oil on the finned exhaust nut. Dismantled exhaust today. There was quite a bit of oil in the muffler, also in and around valve guide and valve steam in the exhaust channel. I would suspect worn out valve guide but since I am not familiar with the design perhaps there might be something else.
There is no blue smoke so it’s rather not oil form within pistons and there is no leak from valve rockerbox cover.

It’s happening only on right cylinder, left seems fine. Compression is exactly same on both cold and hot.

Please share your ideas.

Best regards
By Jakub
Thanks guys. The thing is I have just removed the head, put it vertically, filled exhaust up to the brim with kerosene expecting seeing some seeping into the rocker room. Nope. Nothing. Not a drop.
I have also tried somehow seal exhaust port, pump the compressed air and use leak checking compound on the other side to find possible cracks in the head itself. None found.
Mystery continues.
By Daiwiskers
It would hold up to a liquid test if the guide or valve stem is worn

To be honest I would look into replacing both valve seats and guides on both sides

Good luck with it Dai
By Jakub
Daiwiskers wrote:
Mon Jan 24, 2022 5:28 pm
It would hold up to a liquid test if the guide or valve stem is worn

I very much hope you are right, taking the head to the machine shop tomorrow, hope their diagnostic capabilities will yield results,

BTW, would you advise taking both heads or follow “ if it ain’t broken don’t fix it” rule
By Daiwiskers
The problem is it is broke just on one side but it's broke
I would take both check for hardened valve seats and measure up the valve stems and guides

If anything is not up to spec get it done now if you just do one side chances are the other will let go within a short time of rebuilding it

Once it's done it's done and is not going to bite you in the backside at a later date

Cheers Dai
User avatar
By Wheaters
Filling the combustion chamber with liquid is only checking the valve and seat are doing their jobs and doesn't really check if the valve guide/stem clearance is allowing oil leakage.
User avatar
By Haggis
I think he was filling the exhaust port and not the combustion chamber.
Filling the port would test both valve stem seals and the valve face seal.
By Daiwiskers
The reason I would have the valve seats done is so it will be able to run on unleaded
The valve guide to stem clearance may well be tight enough when cold and not moving but when hot and moving it may well be working as a pump


Shop for accessories at Hitchcocks Motorcycles