Forum

[Himself]

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.

[Gwilly]

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)

[Haggis]

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

[Revband]

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.