Backcut Transmission Gears

[latheboy]

After a few hours scouring thru old threads I must ask....

Where can I send out my transmission to get the gears undercut?

Anyone have an idea what this may cost?

This place does cycles, maybe they would do my R.

http://www.aperaceparts.com/transmissions.html

[morse250r]

dave moore racing

[86 Quad R]

Originally posted by morse250r
dave moore racing

X's 2

or contact Tim @ Titan Racing Inc :cool:

[gandgracing]

I went with WCR (Whitaker Custom Racing). Did a good job but customer service wasn't very good.

[atvmxr]

arent backcutting and undercutting 2 different things?

and why would you need this on a TRX, it already shifts so damn good. just wondering?

[latheboy]

I understand backcutting and undercutting to mean the same thing-- to undercut the dogs on the gears so when they are engaged with each other, the undercut angles hold the gears together. (see the photos in the link i originally posted) A friend of mine had this done to his 450r, and it is basically impossible to miss a shift. If 2 undercut dogs come together, they will engage.
I agree, my 250r does shift very nicley, but i plan on building a 60hp+ engine, and I would hate to unleash that kind of power on 2 gears that are not fully engaged with one another.

[Honda 250r 001]

What does this usually cost to get done? Do they do all gears? Looks like a nice mod to me im thinking about getting this done for just peace of mind.

[gandgracing]

At my first climb with the Puma I got to the top of the first breaker, let of the throttle and then stabbed it again and second gear came through the left case. When you let off the throttle the gears will seperate some and slam back together when you gas it. Undercutting holds them together in gear.

[Honda 250r 001]

Originally posted by gandgracing
At my first climb with the Puma I got to the top of the first breaker, let of the throttle and then stabbed it again and second gear came through the left case. When you let off the throttle the gears will seperate some and slam back together when you gas it. Undercutting holds them together in gear.

not only does it keep it it gear, the gear it selfs keeps its self in place, so the shift fork is not doing that job, so its not wearing on the fork as much, resulting in a longer lasting tranny.

[latheboy]

Just from riding a 450r with cut gears...there is no way to half shift it. It just seems to shift more postively. I would say its worth it if you have higher hp.

I am sure that you need to cut every gear in the transmission that dogs with another gear. For my application, I would need both sides of the dogs cut. This would make the angles effective for both upshifts and downshifts. I do downshift hard sometimes coming into the corner on the ice oval....

I am wondering what it will cost also.

[morse250r]

my dave moore racing tanny its an override but its backcut you could do it yourself all they do is put a 45 degree angle on the dog legs give him a call and ask him he will take your call and has all the time to talk to you

[atvmxr]

oh over-ride, thats the other mod I was thinking of. with an override dont you have to shift WFO all the time? its mainly just for straight line drag racing??

[1promodfan]

Originally posted by atvmxr
oh over-ride, thats the other mod I was thinking of. with an override dont you have to shift WFO all the time? its mainly just for straight line drag racing??

Yea, an override allows you to shift without pulling the clutch. It is mainly a drag setup. You can't unload the motor on the gears though, if you do, you can toast your whole tranny. When drag racing, after you get to the end of track you have to pull the clutch lever in and come to a stop before gearing down.

With the Banshees, they have a dune-able override that allows you do down shift and also you can let off the throttle at certain RPM's. I've heard of guys trying to do one for a 250R, but so far no luck.

[derby]

Originally posted by 1promodfan
Yea, an override allows you to shift without pulling the clutch. It is mainly a drag setup. You can't unload the motor on the gears though, if you do, you can toast your whole tranny. When drag racing, after you get to the end of track you have to pull the clutch lever in and come to a stop before gearing down.

With the Banshees, they have a dune-able override that allows you do down shift and also you can let off the throttle at certain RPM's. I've heard of guys trying to do one for a 250R, but so far no luck.


I had something similar happen to what gandgracing said. I ended up using WCR also and it was great. But I actually spoke to the guy who cuts the tranny's not his wife or sister whoever answers the phone. I just cut 1-4 and had the trans treated. Treating, cutting all 6 gears on both shafts will run you about $250 with shipping. My trans came back and it looked brand new. they cryo and did some type of heat treatment on trans , shift forks, drum, and both main and cs shaft. Most people would not need to have it done. But my puma ate the 1st set of yukons really fast. After destroying 5 gears(3 or which were yukons), 2 shift forks, and bending the counter shaft I had to try something else. Before when the motor was under load and lets say it got short shifted it would automatically try to drop to the lower gear. It does shift much smoother and requires less effort/skill to be consistent. I know of another shop that will cut all 6 gears and cryo for $450-$500 but the choice was clear to me. WCR only does trans and that is what they specialize in.

[250rPRIDE]

ya i have used override trannys on banshee's and a 450r they are a little scary at first, i didnt want to buy a new trans by backing out of it half track..:eek: but theres no other way to go with a drag bike.. but this under/backcutting the gears sounds interested..is it nessasery for a heavily modded stock cylinder 250? i would guess i am about 40-45 horse?
keep the reviews coming this is interesting!

[derby]

Originally posted by 250rPRIDE
ya i have used override trannys on banshee's and a 450r they are a little scary at first, i didnt want to buy a new trans by backing out of it half track..:eek: but theres no other way to go with a drag bike.. but this under/backcutting the gears sounds interested..is it nessasery for a heavily modded stock cylinder 250? i would guess i am about 40-45 horse?
keep the reviews coming this is interesting!

It is a problem if you are running a puma. I know of 5 different 431 puma's that have already been through a transmission. 4 of them were non-over rides set up for dune or hill climbing.

[rrguy]

These guys were recommended by Arlen from LED racing I think I got the right place.

R&D Motorsports in Florida

(727) 447-4552