Hitchcocks Forum

A rebore to +60 might be needed for my bike. Could anyone supply me with the appropriate measurement/s so that I can pass them to the engineering shop I will use. The manual for the Indian bikes says the standard bore size is 69.875 mm or 2.751 in; is it the same for Redditch models? I know I could buy a workshop manual and probably will eventually but if anyone could supply me with the information it would be greatly appreciated. A copy of the relevant page from the manual would be excellent if possible but any assistance would be appreciated. Many thanks in anticipation.

According to Pete Hartley and Roy Bacon.

Both 250 and 350 have a standard bore of 70mm.

Rebore 0.020" (0.508mm)

Piston ring gap 0.011"- 0.015" (0.257-0.381mm)

Your engineering shop will measure your new piston and rebore with the appropriate clearance.

Modern engines use far less piston bore clearance, you need an old school machine shop who understand old bikes if they are to measure the piston.