Spigot length, 350cc Barrel for w/ng

[stevewhitt]

Hi
Im trying to chase down the reason why my head doesn't seat correctly on the top of the spigot. Measuring from the surface of the head into the step of the shoulder reads 3.86mm whereas the length of the spigot is only 3.26mm. Clearly, it is never going to mate! I am currently waiting for a copper gasket to solve the problem, but I am intrigued as to where the problem lies. I can only assume the spigot is not a long as it should be, but it does finish flush with the top of the piston, although the spigot could easily be 0.6mm longer and still appear so.

Does anyone have a head off at the moment who could measure their spigot protrusion?

I did read somewhere, although I am not sure it applies to my head that sometimes the liner slips down - is this possible?

Thanks

Steve

[Roger Gwynn]

The liner isn't a separate part unless your cylinder has been re-sleeved but then it is not likely to be as large a diameter as the spigot. The recess in the head should be 5/32 deep +/- .005 and the spigot on the cylinder should be 3/16 +/- .005 above the surface of the cylinder.

[stevewhitt]

Thanks Roger
That clears that up then, someone has ground down the spigot! Probably because they didn't understand the metal to metal mating surface principle of the Ariel.

My copper washer will address the problem.

Steve W

[nevhunter]

The GOOD, almost FOOLproof method of sealing a head joint. Make sure it doesn't have an overly thick sleeve in it. They are likely to break off the flange if that is done . The 350 is not the strongest of cylinders Perhaps KAROL could make some good ones. It's a simple enough pattern. Nev

[Bob.Murphy]

Steve, do you have an original barrel or is it an after-market item?

I ask because I had the same issue with an after-market alloy barrel on my VH. The previous owner had fitted a copper gasket to make up the difference.

Being me, I removed the barrel and milled the top of the barrel to give the liner the proper height (I think I left the liner 10 thou' long so the head could be lapped and pulled down evenly).

The compression is now much higher than it was, thanks in part to fitting a 7.5:1 piston. It shows-up the inadequacies in the silencer !

Bob.

Ooops, the pictures are sideways - hopefully they will straighten-up when clicked on.