HomeTechnical ReviewsRepairing the Hayabusa Transmission - Part 2

Repairing the Hayabusa Transmission – Part 2

If you haven’t already, read Repairing the Hayabusa Transmission – Part 1

I was told when I received the transmission it would look so good I would not want to put it in back in my engine. That was an understatement. This thing is a mechanical piece of art when compared to the way it looked when I sent it to R-D Motorsports. As good as it does look; it will be hard to race with it sitting on my mantle.

What was done…
The first thing R-D Motorsports did was logged in the fact they received my transmission, then proceeded to disassemble it and mark all the parts with my initials to keep them from ending up in someone else’s transmission. Next a magnaflux bath was in order to find those pesky cracks which go unseen by the naked eye. Most of these cracks show up around the oil holes on the input shaft and sometimes the output shaft.

Next my output shaft run out was indicated to make sure it was straight and the clearances were checked. Mark does not like to let anything go that is out more than a couple of thousandths. At this time a few tricks are done to accommodate better circlips to keep the gears where they are supposed to be. The factory circlips have a tendency to jump out of their slots under the heavy loads seen in drag racing.

At this point if any problems are found you will receive a phone call as to what they are along with the cost of replacement and the estimate on total repairs. If any parts are needed R-D Motorsports has a majority of the popular parts for most transmissions in stock.

The next phase involves undercutting, deburring, heat treating, cryo freezing, glass-beading and coating the transmission parts. Then the parts are cleaned and taken to the clean room for assembly. During this process my input shaft was given the optional cryo deep freeze to squeeze those atoms into a tighter matrix, strengthening the input shaft considerably.

How it works in the bike
When you look at the transmission you can obviously see the detail in the workmanship that was done to the machined surfaces. The dogs were polished and tapered to aid in faster engagement. The backcuts had perfect mating surfaces. But would I be able to feel it once in the bike?

Amazing is the word I would use when describing how it actually works at the track. You can definitely tell the difference in feel. The bike does not so much feel as if it is changing gears when going down the track but feels more like it is just constantly accelerating. Each time you hit the airshifter there is no delay or bang but just a seamless shift. It truly is incredible.

The first thing I did was turn my MPS kill box down after the first run. It was set in the middle and now it is about a ¼ turn less. If I was guessing I would say somewhere in the 30 millisecond range. The one thing that stuck out each time I went down the track was how smooth it was. No chain slap or bucking or anything.
Just smooth.

More information on a potential problem
Jay Eschbach from APE sent me an e-mail in response to the first part of this article outlining another issue he has seen in regards to the Hayabusa shift fork shafts.
Apparently, if the shift forks are flexed too often from hard shifting in race applications or 2nd gear popping in and out it causes the factory shift fork shafts to bend. When this happen the holes the shift fork shafts go through in the cases start to elongate rendering the crankcases useless.

This is why APE as well as Brock’s Performance offer aftermarket shift fork shafts. The APE shafts are solid tool steel while the Brock’s are of billet construction. Both are made for race applications and designed to stop the problem Jay mentioned.

What does it all mean?
Peace of mind mostly. Mark told me to forget about the transmission now and worry about racing. After all you are only as good as your equipment. It is hard to be consistent when the bike is not; all of us who race know that.

Lower kill times make up hundredths in the ¼. Smoother shifts are easier on engine internals, sprockets and chains. Combined it is a win win situation for you and the bike.
So if you drag race and start feeling 2nd gear clunking, think about saving money in the long term by having the complete transmission done right. You will not regret it.

See ya at the track!

Paul Cavanaugh

www.hayabusazone.com (APE)

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