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Discussion Starter · #1 ·
Hi everyone, not been on for a while but I have lost 4th gear on my 954 and as I am going to have to split the engine to replace gears I am going to do another engine rebuild while I am in that far.
I have some questions with gears, has anyone had their gears cryogenic treated (or similar) for extra strength, I was hoping to get them race-cut to cope better with abuse and because of the work involved with fixing a bad gear, but I cannot find anywhere in the U.K to do it and I am thinking cryogenic treatment will surely be available here. Another gripe I have is the first gear is too short compared to second and would like to put a taller first in while doing the work, it is not a huge issue on the road although still annoying, but on track when dropping into first going into a tight corner I have to manually slip the clutch to stop the rear wheel chattering (no slipper clutch fitted as yet) so has anyone here installed a taller first?
Thanks for any input, I will upload pics of the build as I go.
 

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Discussion Starter · #4 ·
How did you find the gearchanges after the dogs were cut backdoc, and did you keep the bike long after that? I was speaking to a road racer today about undercutting and he advised against it for longevity, his opinion was that cutting through the case hardening shortens the lifespan even if they are re-hardened again, would be interesting to hear other opinions on this from those who have tried it for a good amount of time, this was also a concern I had about getting my camshafts re-ground for longer duration, longevity being my worry.
 

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Owned my 954 for another 3-4 years and only used it for drag racing. Never had another missed shift. The factory pro evo shift kit was very helpful too over the stock shift star and spring. As you can see in my thread my gears had lots of wear on the dogs of each gear but were still able to be undercut saving the cost of new gears. There is no need to have them re-hardened afterwards and they will last as long as you have it. Racecut is cutting both sides of each gear to prevent missed downshifts too but I never had any problems when downshifting.

Doing other motor work on a 954 is crazy expensive for very small gains. I had a 50 shot of nitrous on mine which really made a big difference and was much cheaper than cams, oversize pistons and headwork. Its why I built a Hayabusa for drag racing and eventually sold the 954.
 

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Discussion Starter · #6 ·
It's nice to hear that it lasted backdoc, I don't have problems on downshifts either apart from rear wheel chatter going into first gear corners (1st gear being so much lower ratio than 2nd), I have to manually slip the clutch to prevent it as I have never got around to fitting a slipper clutch. I also have the factory pro shift kit on mine and have to say it is better quality than the stock Honda items and makes the gear changes feel more definite. I added the Gilles shaft support at the same time to eliminate as much chance of miss shifts as I could, neither of these cured the fourth gear problem but was worth doing regardless of that as they will help when I have sorted the problem gear dogs out.
I bought the cylinder head for mine from a guy in the states, Gary Medley (formerly involved with these bikes in Formula Extreme) did the work on it, it made a significant change to the induction sound of the bike, went from a gentle bark to a nice growl is the best way I can explain it. Apart from that power wise I went for a full Akrapovic race system, decked the head, B.M.C. race filter, power commander and rev extend mod then rolling road tune, it made 150bhp at the wheel, maybe 165 - 170 at the crank, I altered the airbox too but doubt any gains would be made there. Other mods were cosmetic/weight saving, I have also lost a good chunk of weight so it all helps increase the bhp per kg.
I will be looking at pistons and cylinders when I split the casings to get the transmission out, if they look bad I am considering the 1mm overbore and 980 forged pistons and I agree that it's crazy expensive for not a lot of gain, but it won't be a lot more than new standard pistons and bore, my concern there is going another 1mm on an already thin wall and whether the alusil/nikasil coating will hold up. Plenty to keep me busy anyway, rebuilding my boys YZFR125, a serious case of oil starvation to the point it wore through the rings. :censored:
 

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My 954 completely stock engine with full Hindle high mount exhaust system/bmc race filter made 145hp on 87 octane pump gas. I had a set of Factory Pro velocity stacks and they made less power on dyno so I went back to stock stacks and sold them. The 1mm over pistons in a 954 make the bike run hot and not good for street riding. As for the cylinders every 929/954 made will have scoring from the short piston skirts but this does not affect performance.
 

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Discussion Starter · #8 ·
I believe the later models also suffered with the cylinder scoring, it is annoying to say the least, but is very strange how they keep good compression with the scoring, first time I tore mine down I couldn't believe how badly scored the cylinders were, yet the bike didn't burn oil or suffer from bad compression.
I will be fitting a fan switch to mine for track use as the heat creeps up fast when going into the pits, also changing the radiator as this issue only started after I put an aftermarket rad on the bike, a manual fan switch is also a good backup incase the factory fan switch fails which has happened to me before.
 

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I had a manual fan switch on mine. Think the company that made them went out of business. It required no cutting of wires and tapped onto the fan relay on the right side of subframe. Allowed fan to work normal when switch was off. Worked good for hot days.
 

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Another gripe I have is the first gear is too short compared to second and would like to put a taller first in while doing the work, it is not a huge issue on the road although still annoying, but on track when dropping into first going into a tight corner I have to manually slip the clutch to stop the rear wheel chattering (no slipper clutch fitted as yet) so has anyone here installed a taller first?
 
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