Squish on Jawa 350

[stinkwheel]

I don't suppose anyone has a ballpark figure for the squish on my Jawa 350 do they? It's a bit (well, a lot) like a villiers twin if that's any use.

I'm throwing away the thin aluminium head gasket and lapping in the heads after seizing it (due to timing issues). Squish was never an issue before because I always used carbdoard base gaskets but I've got rolls of proper gasket paper now so I'm using that if only because it is easier to get exactly the right size. There is a surprisingly small gap between the ports and the outside world.

Nothing fancy like tuning it, I'd rather err on 'too big' than 'absolute minimum', just don't want stuff hitting the top.

If I find it needs a head gasket I have some copper sheeting here but if it doesn't need one, no point in making/fitting it.

If anyone has a rough idea of cylinder head torque (M10 odd pitch studs through an alloy, air cooled head), that would be handy too, otherwise I'll just get them the all the same and what feels like 'tight enough'.

[tatters]

[Pete.]

For a steel conrod you need to maintain 1mm of piston-head clearance as a general rule. For an aluminium conrod it's 1.5mm
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[stinkwheel]

That being the case we'll go for 1.5mm minimum, if it's under that it's either getting two base gaskets or a head gasket. It's a steel rod but they are cold-war era Czecoslovakian bearings.