When I pulled the head and barrel off, the studs were rusted and gritty with general rubbish, which can fall down into the crank case when the barrel is removed.
The source of the rubbish is the gap between the top of the barrel fining and the underside of the head, as the head seals on the spigot of the sleeve, not the top of the barrel as such.
There is nothing to stop this rubbish getting in, as it stands, and I have a "cunning plan", which is the purpose of the question.
Have anybody tried fitting a thin silicon rubber (high temperature) o ring into this gap to stop the rubbish getting in there in the first place, carefully sized of coarse to just seal when the head is tight against the barrel spigot.
One problem I foresee already is if the head to barrel seal leaks slightly, the pressure will push the o ring out until the gas can vent, but as soon as the gas stops the o ring will seal back against the head to barrel joint again, which is the desired outcome after all
Top of barrel, before pulling barrel, you can see the rubbish around the studs.
After barrel pulled, lots of rubbish and rust.
Head, showing the stud and bolt holes outside the sealing surface.
Has anybody had this problem?
Has anybody tried my proposed fix?
Can anybody see a flaw in my reasoning and or fix?
