9.14. 800cc Virago cylinder liners

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The title isn't completely correct as you use XV750 Yamaha cylinder liners and pistons (750cc V-twin 'cruiser' style bike)

The original conversion would have used Honda Hurricane 82mm pistons but the compression ration would be unacceptable low (I know because I 'invented' it)

Pistons and liners have to be modified to convert the XS650 into an 800cc motor.

The bottom of liner needs to be shortened to 14mm less than stock 447 type liner, from 140mm to 126mm 

The top flange has to be reduced in diameter from 100mm to 91mm~92mm

Its a pretty involved process which requires the use of Honda CR500 (two stoke motocross bike) connecting rods.

This means you have to also do a full engine strip down, remove, dismantle and re-build the crankshaft. The CR500 rods are 144mm length with is 14mm more than the stock 447(US market) connecting rod. and 4 mm more than the Europe only rods

The rods need bushings in the small end to reduce them to same diameter as piston pins (reduce from 25mm to 20mm)

Anecdotal 'evidence' leads me to believe Yamaha use 144mm rods in Kenny Roberts 750cc Flat track racers which purportedly produced in excess of 100bhp but suffered reliability problems at high rpm (over 10,000rpm) Link to discussion and list of pistons for use with CR500 rods [1] PJ


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