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Are these marks on the piston signs that the cylinder needs a rebore or is there another issue I should be looking for.

The piston has been in the bike for around 200miles the piston and rings were new when installed along with the drive and magside bearings and seals (all good quality and care was taken installing them).

Also what are the tollerances for the conrod movenment (side to side)?

What is a decent make of piston to go fo, any recommendations? I was looking at the GOL ones but scooter restorations dont currently have stock of them. Due to the virus and restrictions I wouldnt have thought they will be getting stock anytime soon.

Any help would be much appreciated.

TIA

Do the marks correspond the stud holes ? What barrel is it ?

Assuming carb settings air/fuel/oil ratio/no air leaks/ timing correct etc? I'd suspect not enough clearance on piston to bore, you say its a new piston, did you check the clearance? although the piston size may correlate to the previous piston/bore quite often different makes of piston will measure up slightly different, also expansion rates etc The marks are slight nips, suggesting the bore clearance is not adequate, look for around 4" thou on (0.1mm), hope you get it sorted!

MickYork wrote:Do the marks correspond the stud holes ? What barrel is it ?

It's a standard barrel 150.

I'm sure it was 0.1mm when I put it in, I'll go out and check it all again tomorrow. Timing was set up at 21 BTDC. Leak test was good too, I'll double check everything again and see what has changed or failed.

retard the timing a little, 19 or 17ish

I couldn't get any further than 21, I'll have to elongate the slots in the stator to rotate it further. Thanks.