Hayabusa Gearboxes

One area that has been found to be a weak point in modified Hayabusas is the stock transmission output shaft. Under extreme loads the stock shaft can break resulting in engine case damage. The Extreme Heavy Duty output shaft is machined from super high strength billet steel.
EXT-10011 Hayabusa Heavy Duty Output Shaft

A direct replacement for the standard six speed gear set. First and second gear ratio’s are as standard, but third gear is 8% higher than second to allow for changes in track conditions and help to establish the optimum overall gearing.

This has allowed us to incorporate many beneficial features in our three speed design.

The most important being to stop the engagement dogs from coming out of mesh under power. This is achieved by having the engagement faces dovetailed which effectively pulls the mating parts together under load. As only three gears are required the new gears are now wider for better durability. Gear changes are effected by the standard selector mechanism but using only the two selector forks acting on the output shaft. The input selector rod and fork should be removed as they are no longer required. Gear changes are made by two selector rings, thus cutting the inertia required to change with the standard gears. The standard input shaft is retained but new gears, spacers and retaining clips are supplied for use in the three speed gearbox.

The output shaft is supplied assembled and requires only the fitting of support bearings. To overcome the problem of output shafts breaking, adjacent to the sprocket, the shaft is manufactured with a larger diameter to take standard Honda sprockets. This will require the standard spacer to be bored to suite the new shaft.

The only other modification required is to stop the selector mechanism from changing past third gear. There are two ways of achieving this, either remove the “pawl pin” from the selector drum which will prevent the mechanism selecting fourth gear or a peg can be fitted in the selector drum to prevent rotation past third gear.

See instructions for modification to selector pawl pins.

If you are replacing a standard gear set which has continuously jumped out of second gear, we would strongly advise that you replace the selector drum and selector forks as a matter of course.

To prevent selection pass third gear remove the pin identified by the arrow.

The only two pins which are operative in the 3 speed gear box are the two coloured in White to the left of the arrow.

WARNING

Do not assemble crankcase using any form of silicone compound.

Only use 3 bond corporation of USA jointing compound, this is sold by Suzuki as Suzuki Bond No.4.
As does Yamaha as Yamaha Bond No 4.

Expensive, but the best.

EXT-00017 Hayabusa 3 Speed Autograss Gearbox

EXT-10022 Billet Selector Shafts Set