How much clearance ?

[380roost]

At high revs the crank flexes slightly, and the rod is a little longer, throw in a bit of bigend wear, and the squish clearance reduces,
what is a safe number.

 

[bclapham]

i go for around 0.7-1.0 mm on my 125 and 250 bikes. i had an odd sizedd gasket once and it was around 0.5mm and even with 110+octane fuel the deto fairy came for a visit!

for that bigger bike i would think 1.0-1.5mm is good, look at erics book maybe for specifics