Scooterotica

Hi all!

I got two barrels in from a customer to have rebored, one for a GS160(VSB1, second over) and a P200E(first over). I also have photocopies of the original manuals for both. The wording is a bit different than lambretta and I want to make sure I've got it correct....

VSB1 clearance on assembly= 0.12mm or 0.0047"

P200 clearance on assembly= 0.215mm or 0.0085".....!!, really? That can't be right, can it? That's two thou over the wear limit on a lambretta. Also, it only gives the assembly clearance, but no wear limit. How do you know when it's too worn for use? I've got to be missing something, which is why I'm asking here. I would think with that clearance the P200 would have piston slap right from the beginning. Can anyone clarify? Thanks!

ive had loadsa P200 barrels re-bored, and always get 4 thou clearance (ive used Frontline motorcycles in middlesborough for tha last 10 years , and before that Armstrongs on westgate road in Newcastle) never had a problem , and I usually just take it easy for 3 tanks of petrol, and leave them on high tickover when I can to help running in. 8 and a half thou sounds excessive though.

Agree with Goldeneye 4 thou all the time for me

3.5 if i could be arsed to run in !

had genuine barrel/pistons and pattern done to this at Frontline and AF

just had a genuine barrel bored to match a thin ring 210 with 4 thou

however Harry Barlow states 5 to 5.5 thou on his pistons in cast barrel

had a look at the red Haynes Manual, and that says 8 thou and the old (blue) manual says the service limit it 0.25mm, whats that? 9 and a half thou-ish, for a Rally 200, same barrel as P200. maybe they just gave this info out to be on the safe side. I would still go 4 or maybe 5 thou at the reborers .

It was ralph saxelby who told me 4 thou and its always worked for me

when i was at AF to get a bore done on a vespa barrel Ben asked what clearance and I told him 4 thou - he agreed - it was that worn when he measured it he just managed it with the first oversize piston and commented if had been any more he would have suggested going second oversize.

Thanks guys! I'll shoot for 0.004-0.0045" then. I knew 8 thou seemed way big!