Sample Virago Displacements

Redline is reckoned at a piston speed of 4000 feet per minute.   High-chrome valve springs, lighter valves, and other modifications can raise this to 5000fpm, no problem. Modern European twins exceed 5500 FPM; Formula One car engines pass 6500FPM.

To find the speed at which the pistons hit 4000fpm divide the stroke in millimeters into 609,600. For 5000fpm divide it into 731,520; for 5500fpm into 804,672; and so on.

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Warning: the smaller bikes have very little metal above the rod eye, where the piston pin resides. Going over 84mm (767cc) is not a good idea; the rod small-end could conceivably snap. If you want real displacement, install rods from the 920 on up XV line. Not XVS1100 rods. Then you can open the apertures in the cases as far as you like and run the appropriate pistons. Better yet, just buy a larger model or a more modern twin.