Scooterotica

nar it is 4.7 but is the piston new? they ware at the skirt much faster than the bore does. If the piston has been run I would put a new piston in it and thrash the life out of it as 4.5 thou is ok, it might rattle a bit when cold but once up to temp I'm sure it would be fine

OK so feeler gauge down one side pushes piston over and measures total clearance. I agree 4.7 (but still 2.35 either side.)
I take forever to measure pistons..Top bottom middle. ..rotate etc etc and I end up with a lot of numbers crossed out !

no its a used piston, kits done about 1500 miles I believe possibly 2000.

So, go for a standard rd350 piston? are there any particular makes to avoid, google seemed to prefer one by Pro X though have also seen wossner mentioned as good?

Aside from that, what about the piston ring issues?

chuck a new piston in and just run it.
you can get a new piston from Richard. they are cheap!

Think that's exactly what I will do

Easy tiger! I smell a rat.

You have measured a standard bore and standard piston. I will go and measure the same now and check the rings from new.

Here you go
Piston skirt dimension 63.91mm
Bore dimension (taken at top as the skirt can move) 64.00mm
Ring gap 0.45mm (18 thou)
Bore clearance 0.09mm (3.6 thou)

Ahh, so in fact mines within usable tolerances then after all richard?

yep, I don't often get asked about ring gaps. If you're worries about it send the rings back and I'll credit your account

Don't be daft man, I ride my scooter not van it, they're my service set for when these ones are worn out