stage 4 cast barrel kit

[scootjohn777]

Hi all, I bought a stage 4 225 cast barrel kit complete with head and racetour piston.had a local dealer(who's a mate) to fit the kit to a new 200 casings using a g.p. 150 doner engine along with uprated clutch, sprockets,chain,revtour exhaust,and a 30 mil dellorto.But recently it's become a nightmare to start, taking up to 30 kicks to start!!! but once started seemed to run fine.Checked timing, adjusted jetting, it's only done 500 miles but the compression which was never very good seemed to be getting less and now I can push the kickstart down by hand, so I removed the top end today and the piston seems too small??? and the rings seem too small for the piston also??? with the barrell off the scoot I can insert the piston with the rings and the piston will literally fall out without any pressure at all, I'm amazed it even started in this state??
Could anyone give me an idea what the tollerances should be please? So I can check them when they send me a matched kit......just in case.

All the best and thanks
John

[shocky]

could be loads of things ;have you had your petrol tank sand blasted ? some barrels (spanish autisa ones) are very soft ,are the rings chrome ones they could be to hard for the bore,dirt/dust in the open mouthed carb wearing everything , were did the kit come from maybe ask them if they have had any probs with like for like kits

[camel]

0.0035" clearance for a cast cylinder

[J1MS]

3.5 to 4 thou piston to bore clearance (approximate), piston rings should be about 12 thou end gap new, at 30 thou they need replacing...thats for a cast iron cylinder...

[scootjohn777]

Thanks for the info folks, I have a new stainless tank on the scoot and it has been running with an air filter too, it must just be a mismatched kit I think? It's going back today for them to have a look at it.

all the best
John