Running in information after rebuildi

Hi paultz

Attached is part of the Villiers 2T Instruction Manual which covers 'Running In'.

There does appear to be a problem with bikes being rebored with insufficient piston skirt clearance. We have honed out quite a few barrels on bikes that have been rebored and then suffered with nipping up problems. I know the 325cc 3T engines fitted in Greeves were very susceptible to nipping up particularly when they were fitted with the 2 into 1 exhaust system. The alloy beam frame and 2 into 1 exhaust tended to shield the engine from cooling air and they ran hotter. To overcome the problem the barrels had to be honed out to the point where according to the manufactures information they were worn out. However the engine then ran without any problems.

As most of us do not ride many miles in a year, running in a rebuilt engine can be a frustrating process that can take all year or longer. If the engine suffers from nipping up during the running in process it can take forever and you risk the piston rings becoming trapped in their grooves.

It your engine suffers from nipping up problems get the barrels honed out to give 4 thou clearance at the bottom of the piston skirt. Hepolite recommended 1½ thou per inch of bore diameter for air cooled two stroke engines and the 2T is approximately 2½" bore, which would give 3¾ thou.

I hope that the attached information helps you.

Regards
Butty Bach