CBR 954 Undercut Transmission - Honda Motorcycles - FireBlades.org
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post #1 of 17 Old 10-03-2014, 10:23 AM Thread Starter
 
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CBR 954 Undercut Transmission

I almost made it through this years drag racing season before my transmission finally let go. It got to the point where it would not shift into 2nd, 3rd or 4th gear at high rpms. Normal riding it would do ok. After removing the engine and splitting the cases I figured I would have to replace gears 1-4. While talking to my racing buddy he said my old gears could probably be undercut saving me the cost of buying new gears at $60-80 per gear. He called one of his sponsors who runs a machine shop and he said send it to him and he would check it out. Turns out even my old worn gears were still good enough to undercut. I got a great deal since my buddy knew the guy very well. Normal price for undercutting a transmission can range from $300-450. When you figure the price of new gears would be around $250-400 depending on how many need replaced why not just get your gears undercut instead of replacing them and hoping it does not wear out again. All the gears on both the input and output shafts were undercut but only for upshifting. If you do alot of track days then you may want both up and down undercutting.

Pics below are my stock gears before and after undercutting.
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post #2 of 17 Old 10-03-2014, 2:46 PM
 
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Re: CBR 954 Undercut Transmission

Undercut means cutting just the side that is affected when shifting up. Race cutting is when they are cut for shifting up and down. Mine are allso undercut and few of the gears are allso cut for downshifting. My bike never shifted better. Haven't missed a shift since and it was little bit hard to shift properly before the gearbox was repaired. Any other mods since you have splitted the casings?
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post #3 of 17 Old 10-03-2014, 3:07 PM Thread Starter
 
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Re: CBR 954 Undercut Transmission

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Originally Posted by mika_u View Post
Any other mods since you have splitted the casings?
No performance mods just some maintenance. I need to get it back together before next weekend so I don't miss the last few drag races for this year. I have to adjust the valves because all of them are very tight and below spec. This is the first time they have been checked at 34k miles and my valve clearances are .004 intake and exhaust .008 thousandths. Also going to install a new cam chain and tensioner while the camshafts are out.

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post #4 of 17 Old 10-03-2014, 3:11 PM
 
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Re: CBR 954 Undercut Transmission

Reading what mika wrote, I guess mine are race cut. Who did your work backdoc? I sent mine to R&D in Florida.

http://www.r-dmotorsports.com
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post #5 of 17 Old 10-03-2014, 3:24 PM Thread Starter
 
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Re: CBR 954 Undercut Transmission

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Originally Posted by Mikeo View Post
Reading what mika wrote, I guess mine are race cut. Who did your work backdoc? I sent mine to R&D in Florida.

Home - R&D Motorsports
I used Xtreme Motorsports in TN. They do great work and I had it back in 1 week. There was no need for me to spend the extra money on a race cut for drag racing plus I never had a problem with my bike jumping out of gear while downshifting.

Xtreme-Motorsports | Full Service High Perfomance Motorcycles Services

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post #6 of 17 Old 10-03-2014, 4:16 PM
 
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Re: CBR 954 Undercut Transmission

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Originally Posted by backdoc View Post
I used Xtreme Motorsports in TN. They do great work and I had it back in 1 week. There was no need for me to spend the extra money on a race cut for drag racing plus I never had a problem with my bike jumping out of gear while downshifting.

Xtreme-Motorsports | Full Service High Perfomance Motorcycles Services


Good deal! Now some forum members will at least have a choice and some contact info in case they are looking.
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post #7 of 17 Old 10-04-2014, 5:45 AM
 
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Re: CBR 954 Undercut Transmission

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Originally Posted by backdoc View Post
I used Xtreme Motorsports in TN. They do great work and I had it back in 1 week. There was no need for me to spend the extra money on a race cut for drag racing plus I never had a problem with my bike jumping out of gear while downshifting.

Xtreme-Motorsports | Full Service High Perfomance Motorcycles Services
Actually the jumping out of gear would happen when braking with the engine but for that the dog would have to very worn. There just isn't that much load for the gearbox to slip out when braking with the engine. But allso it would affect the how the gears engage when shifting down. Mine didn't engage properly with some of the higher gears when shifting down. It went to "neutral" before it was cut. But i'll get the rest of the gears cut for down shifting next time i have the casings apart. The feel is little clunky with gears 1 and 2. And it doesn't shift down nearly as good as up in all gears and i love the way it shift up so i would like it to shift down the same way.
I were in a little hurry to put the engine back together when the gearbox was cut so for the down shifting was cut only the gears that were absolutely necessary. Shouldn't never rush with these things. No i regret they weren't done last time
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post #8 of 17 Old 10-04-2014, 9:49 AM Thread Starter
 
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Re: CBR 954 Undercut Transmission

Quote:
Originally Posted by mika_u View Post
Actually the jumping out of gear would happen when braking with the engine but for that the dog would have to very worn. There just isn't that much load for the gearbox to slip out when braking with the engine. But allso it would affect the how the gears engage when shifting down. Mine didn't engage properly with some of the higher gears when shifting down. It went to "neutral" before it was cut. But i'll get the rest of the gears cut for down shifting next time i have the casings apart. The feel is little clunky with gears 1 and 2. And it doesn't shift down nearly as good as up in all gears and i love the way it shift up so i would like it to shift down the same way.
I were in a little hurry to put the engine back together when the gearbox was cut so for the down shifting was cut only the gears that were absolutely necessary. Shouldn't never rush with these things. No i regret they weren't done last time
Do you have the Factory Pro Evo shift kit in your bike? It really changes the feel of the shifting from the stock clunky shifting to a more crisp shifting. In my opinion its one of the best upgrades for a 929/954.

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post #9 of 17 Old 10-04-2014, 1:38 PM
 
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Re: CBR 954 Undercut Transmission

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Originally Posted by backdoc View Post
Do you have the Factory Pro Evo shift kit in your bike? It really changes the feel of the shifting from the stock clunky shifting to a more crisp shifting. In my opinion its one of the best upgrades for a 929/954.
Yes i do. I allso have a solid billet shift shaft and barnett carbon fiber clutch kit with stiffer springs. Clutch basket and center are allso in pretty good shape. I got them from my friends low mileage spare motor when i built my motor. To bigger gear it shifts like a dream but few of the gears don't feel so good when shifting to other direction. Just too much wear on the dogs.

Last edited by mika_u; 10-06-2014 at 6:53 AM.
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post #10 of 17 Old 10-06-2014, 6:53 AM
 
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Re: CBR 954 Undercut Transmission

Have to correct little the terms. I remembered them wrong. Racecut is just fur up shifts and up and down cut is when they are cut allso for down shifting.

APE - Transmissions
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post #11 of 17 Old 10-07-2014, 8:17 PM
 
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Re: CBR 954 Undercut Transmission

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Originally Posted by mika_u View Post
Have to correct little the terms. I remembered them wrong. Racecut is just fur up shifts and up and down cut is when they are cut allso for down shifting.

APE - Transmissions
Eh, whatever the name, it's a good idea to do to a trackday or drag bike in my opinion. I am adding a quick shifter to my bike and having my tranny redone will at least give me peace of mind when beating up on the old girl... oh, and I also have the Factory Pro arm and star installed so I am about as bullet proof as I can get until I either find a slipper clutch or buy a billet basket.
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post #12 of 17 Old 06-25-2015, 10:46 AM
 
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Re: CBR 954 Undercut Transmission

I dont see the difference in the pictures.
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post #13 of 17 Old 06-26-2015, 12:21 AM Thread Starter
 
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Re: CBR 954 Undercut Transmission

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Originally Posted by 02CBR954AD View Post
I dont see the difference in the pictures.
The first 6 pics are of the stock transmission gears. When you undercut a transmission you cut angles on the inner/outer dogs that engage the gears together. The large outer part of each gear is not the part that gets worn and causes missed shifts. Compare the 2nd pic to the 7th & 8th pics and you will see the angle that is cut on the small gear dogs that mesh together you shift. With these slight angles once the two dogs meet they suck together locking the gears. Only way to disengage the gears is to lift off the throttle. The stock gear dogs have nearly flat sides compared to the angle of an undercut transmission.

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post #14 of 17 Old 06-26-2015, 10:56 AM
 
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Re: CBR 954 Undercut Transmission

How precise does the angle need to be, what I mean is, would this be possible for a competent d.i.y'er, or does it need done by a specialist only? Had never even heard of this before reading on the forum!
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post #15 of 17 Old 06-26-2015, 11:29 AM Thread Starter
 
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Re: CBR 954 Undercut Transmission

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Originally Posted by tahitian954 View Post
How precise does the angle need to be, what I mean is, would this be possible for a competent d.i.y'er, or does it need done by a specialist only? Had never even heard of this before reading on the forum!
I would not recommend trying to do this yourself. The angles need to be precise for everything to work correctly. Best to pay someone to do it right so you don't destroy the entire transmission. There are different cuts for the transmission. Undercut is only for upshifts where racecut cuts both sides for up and down shifts.

A transmission that has worn gear dogs can usually be saved with undercutting and feel better than new instead of buying new gears.

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