Engine prop shaft adapter

The Hayabusa engine normally has a toothed gear to transmit the power from the gearbox to the rear wheel of a motorbike. Wesfield in their cars mount a special adapter on the gearbox output shaft that adapts it to a split Sierra drive shaft. The adapter is normally made of mild steel and is rigidly attached to the gearbox shaft via a large M20 lock nut and a large washer. If you trawl the forums this nut comes undone with amazing regularity. Mine unwound at Croft on 7th June 2014. It was trailered back home as I had no chance of repairing it at the trackside. The mild steel adapter was badly damaged and I did not want the gearbox shaft to go the same way.

I took the advice of Andy at AB Racing. He has a special adapter made to his exacting requirements which is reported to solve the problem. It is designed to be loose fit on the gearbox shaft unlike the Westfield part and is made of hardened steel.

It is unfortunately about 10mm shorter than the original Westfield part so I had to make an alloy spacer in the lathe to make it all fit back together.

The M20 nut was also modified to make the adapter a loose fit on the shaft and I tightened it up such that it will not come off again. I used the permanent nut thread fluid to bond it up tight.

I have no idea if this will permanently solve the problem but is seams like a good approach. Time will tell.




Westfield adapter after failure

Gearbox splines

10mm custom spacer



Nut modified on right to remove some of the step



Reassembled

Update 11th Sept 2014

Kept a regular eye on this part of the car and it regularly gives an 1/8-1/2 turn between race events on the cap head screws no evidence of the 32mm nut loosening again. I decided to wire the bolts to ensure they don't come loose again. I drilled the cap heads in place using some carbide burrs (long job).

Wide carbon wings

I was having difficulty changing the tyres at the trackside with the standard Westfield wings. I was also having difficulty sourcing wider wings. Carbon Copies (Warren Sheridan) made me new ones in carbon. Unfortunately due to ill health he has had to give up his business. It took a long time to get these parts but he came good in the end with the help of his son. Top marks for commitment right to the end. The wings now match the headlights, see bottom image.



From front

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Dynamometer Test

The last open pit lane session at Knockhill with the Westfield club revealed some performance issues on the straight from Taylors up to Duffus. Every time I changed up the power was taking too long to build up again. I took the car to Sitech to find out what was going on. Simon revealed that in the lower (throttle openings) and high engine revs it was being over fuelled. The theory is that this was throttling the engine when lifting off to change gear. Simon completely remapped the Power Commander such that at all throttle openings and rev ranges the correct fuelling was being delivered. All I need now is a track day coming up soon to try it out. Simon did say tht the power sensor on his Dyno is playing up and could be 10-20% down in absolute numbers. I have pencilled in another session after Croft.

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