HomeTechnical ReviewsHayabusa Engine Rebuild for the 2010 race season Part 2

Hayabusa Engine Rebuild for the 2010 race season Part 2

Hayabusa Engine Rebuild for the 2010 race season Part 2


CP Pistons bent over backwards getting me a set of custom 11.0:1 pistons made on late notice, although, when they came it only gave me three days before the AMA Dragbike opener at Valdosta to put the engine together, get it in the bike and put it on the dyno. Now I know a bunch of you reading this (Chad Otts) are thinking to yourself, “So what is the problem?” None for some of you, for me, I prefer to choose the path of least resistance, which was calling my brother, Michael Tlapa and asking if I could borrow his bike.

I have to thank Brock Davidson for generously offering me the use of his Brocks Performance Diary ZX-14 for the Valdosta race, but I had to decline mainly because he had run a 9.2 on it and I did not want to run a 10.4 foot shifting and riding wheelies down the track. Also, I have to thank Jim Walker for offering me his ZX-14 which I seriously considered using since it is stretched and has an air shifter, but ultimately refused because I could not bear to think of him loading it up in his truck after just having an ACL operation and wearing a bionic leg brace. Most of all, I was afraid I might actually like the ZX-14 more than the Hayabusa and all of the work I was doing on my bike would be a waste.

Bearing Sizing

Any of you who build Hayabusas for a living as opposed to a hobby already know what I am about to discuss, so bear with me.

The crankshaft and cases of the Hayabusa (I am sure on other engine manufacturers also) have codes which determine the bearings sizes to use when building the engine. In the service manual there is a matrix in which you match these codes from the crankshaft in one column and the codes from the case to another column and where they meet tells you which main bearing to use. This applies when matching the bearings for the rods also.

Even though this seems like an easy and surefire system to pick the right bearings, it is by no means a substitute for Plastigage. If your crankshaft has been polished or machined in any form or fashion or the rods are aftermarket you can bet the bearings will have to be sized.

There seems to be a wide consensus as to what clearances should be adhered to when building an engine. Most of it is based on the application the bike is to be used in. For street riding, the clearances specified by the manufacturer will suffice. For racing in a Supersport class some builders told me they like to run the rod bearings at what would be considered the “maximum wear” point specified in the service manual. In other drag racing applications some builders use the thinnest available bearing for the rods which would cause them to be as loose as possible and try to keep the main bearing oil clearance towards the middle of the “standard tolerance” as mentioned in the factory service manual. The danger is when all the bearings are too loose oil pressure will suffer. It is all about staying on the edge without going over.

It took me 8 hours to size my bearings and 3 packs of Plastigage before I was satisfied with the bearing clearances. When doing this process it is extremely important that the crankshaft or the rods do not move at all or your readings will be incorrect. It is also important that you follow the complete torque sequences and torque values for the rod bolts and main bearing bolts as specified by the manufacturer or the aftermarket parts supplier. Not doing so will result in poor readings.

Care should be taken to keep the bearing surface clean when using Plastigage and make sure it is completely wiped off when finished. Using a soft cotton cloth with brake cleaner and lightly wiping off the bearing only where the Plastigage is works well. Try not to wipe the dull finish off the bearing.

And if you do not want to waste all that time you spent sizing your bearings once your engine is together and running be sure to change your oil frequently…

To the Dyno…

Brian wanted me to break the motor in on his dyno as it is a good place to monitor what is going on, plus it is always exciting to watch a motor blow up in person. For me, the dyno room is always nerve racking, it just sounds strange listening to your engine screaming in a small room while the bike is stationary. At the same time it is very interesting to watch the numbers after each pull.

There was nothing done to this engine any different than last year other than the head Race Machine had put the skulls in and changing from R-Tech V110 fuel back to VP C-16.

Also the dyno room temperature was different from last year’s session at the end of the season, it was 78 degrees then and 89 – 93 degrees for this test.

Last year at 6 lbs of boost we had 234 HP this year 242 HP. Last year at 10 lbs of boost 270 HP this year 283 HP. (We actually had 295 HP at 10.5 lbs boost but I took out a half pound.)

The amazing thing is the fan on the bike never came on the whole time on the dyno. The temperature gauge always sat right in the middle. Last time the bike was on the dyno we had to shut it down every 40 minutes or so to let it cool down, not this time, Brian just kept running until he was finished with the map. And the room was 20 degrees hotter! My only regret is not having a prior EGT and a post rebuild EGT reading.

At first I attributed the low temperature to going back to the C-16 fuel, but I had run C-16 in 2007 on the dyno and we still had to turn the bike off to let it cool in between runs. In 2008 the R-110 fuel also had to have intervals to cool.

I thought it might also be because of the Motul MoCool, which does make the bike run much cooler, but it was in the bike on the pulls I made last year also.

I have to attribute the temp drop to the AMPCO 45 skulls in the head.

The Track…

The Elmer Trett Nationals would be the testing grounds. Being that I like to ET race I was not at all interested in how fast the bike would do the quarter mile. I am mainly interested in trying to repeat the same thing every time, but I would be lying to you if I said I did not want to make an 8 second pass at some point. I mean come on, it is a turbo Hayabusa, are there any out there that do not run 8’s?

Yes, mine.

The best pass I made was a 9.16 at 155 on my first pass Sunday morning. It is the quickest I have ever had the bike so far.

Maybe in Michigan…

See ya at the track!


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