> how to increase cc on a motorcycle?

how to increase cc on a motorcycle?

Posted at: 2015-04-14 
cc is a measure of 'displacement', the swept volume of the piston in cylinder. That is determined by bore/diameter of piston/cylinder and the length piston travels from top to bottom of 'stroke' of crankshaft turning 180 degrees. Increase either bore or stroke and you increase 'displacement' Most common way for size increase in after market is a larger bore- meaning new cylinder and piston kits as was often done for 2 strokes or a ream out the cylinder and new piston/rings to match the machined out size. Machining tolerance varies- 1mm- 2mm on iron Harley's- is about it and some cylinders are NOT machinable practically- the Nykasil coated ones as example. A easy way to increase CC on the motorcycle? get another, larger engine of same engine case family if possible. New Crankshaft is another method- my old BSA chopper had a Root crank with increase stroke- engine with stock bore was a 710cc instead of 654cc. the large bore cylinders would take it to 850cc, a bore job on stock jugs would have been another 1mm-1.5mm and a 750 nominal engine. I did a 1mm bore on a Honda 100 trainer a few years back- cheap purchase with holed piston and taper of + .028/ 032 - so the convenient over bore was the second step up .040/1mm piston- turned it from 98cc to 112? Old Harley trick for the 74 to 80 incher was us a UL crankshaft in the early panhead case 1948 to 1952- direct fit with straight bearings 1953 and later meant the Timken Tapered bearings and newer shafts needed or a later conversion bearing kit. S&S flywheels started with a UL crank pattern for the later Timken tapered bearings and the next model step up made bigger engine of pan and shovelheads-- but needed case machining to fit. I've got a old UL crank setting on shelf yet- at least saw it last years cleaning so probably still there- leftover from the 1937 UL rebuild with the .030 over pistons.

The 1949 FLE 61 incher got a UL crank and ended up about 68 inchs..

For a car, you can take the engine block to a machine shop and they can bore it out (make the cylinders bigger). If that can be done for a can then I imagine it could be done for a motorcycle. The question is, would it be cost effective? I don't know that one.


200 might be optimistic.

Read the above article, note especially the paragraphs on Chinese kits.

Increase the bore or lengthen the stroke. Or both.

Bigger bore, longer stroke. Same effect with a turbo or super-charger.

buy a new bike