hi,
currently i'm trying to re-shim the head clearance from 25% to 16% nitro, however i've noticed something 'weird'...

the sleeve is sitting below the engine casing, maybe about 0.3mm below. is it possible and normal?

initially the head shims were 0.4mm, now when i tried to use 0.3mm, the buttonhead doesn't really fit totally into the sleeve as it is prevented from fitting totally into the sleeve by the engine case!

something wrong? seems to me that the minimum head shims got to be 0.4mm or more...

p.s. engine concerned is the nosram rs12speed (aka lrp spec3?).