Undercutting the transmission

[renobruce]

It's been suggested that I undercut my tranny gears since I plan on hopping up my motor on my Beast project GS1000. Do I really need to? I'm not going to be drag racing the bike, just an occasional romp on it. Plus it's $264 per side :shock:

I checked at the APE website to get some info on it. They show a pic of what they do to the gears..... angle cut the notches so they stay engaged. http://gszone.biz/trans.html

I took a closer look at my tranny, and it looks to me that the notches are already undercut. But I'm not sure because I have nothing to compare it to. Mine don't look much if any different to me. Here's some pics. Are they already undercut?

click to enlarge:

[sharpy]

gears

Cant really see and i would like to say. Take it to your local expert and ask them Also welding 2nd gear so it doesnt spin is a option. I had all that done on my andit goes thru countless upshifts when its on the back wheel. only missed gears where my lazy foot.

[BadBillyB]

Bruce, yes they are factory undercut. Inspect carefully the center gear on the output shaft. This is 3rd gear. It will be the most worn. My 78 GS1000 that I ride on the street will ocassionally jump from 3rd to 2nd out of the blue and it can really unsettle you when it does this. Sometimes it will go from 3rd to 2nd and then back to 3rd....The motor has 30K miles on it. Knowing it needs work, I pulled out a spare that I have had for 15 years. Careful inspection of the engagement dogs shows that 3rd gear is seriously rounded off....I have been thinking of having just the gears that need re-undercutting done to save on costs.....My spare also showed some wear on 5th gear also....Prices on this type service has doubled over the past 25 years......Hope this helps you......BadBillyB

[BadBillyB]

Bruce, I was kind of suprised by the $264 per side that you mentioned. I was thinking per shaft when you said this. You only need one side done. No need to undercut the "braking" side of the dogs. You will not find any wear there....I am sure APE will do you a fine job. There is a place here in Fla that does excellent work. Give them a call.....There price will be better too......BadBillyB

R&D Motorsports
1632 North Hercules Avenue
Clearwater, FL (Florida) 33765-1936
Phone: (727) 447-4552

[80GS1000]

Up and down cut is good for roadracing where downshifts at high RPMs happen frequently. Up cut is more than sufficient for street bikes. Have you ever had your bike slip out of gear when accelerating at full throttle?

[scotty]

Definitely only one side for drag racing and the like.:-D

[renobruce]

Have you ever had your bike slip out of gear when accelerating at full throttle?

No, never. The 1150 has never popped out of gear. I've only put about 1000 miles on my Skunk since I got it... it hasn't popped out either. That's why I'm wondering if I really need this mod. I'm no drag racer, nor will I be riding balls to the wall all the time. Just an occasional blast when I need an adrenaline rush \\/

[RacingJake]

No need to fix it when it's not broke

If it's not popping out of gear I'd just leave it alone.

[massakins]

I've been drag racing GS1000 streetbikes and both carbed and turbo'd dragbikes since 1983 and have never used a backcut a transmission. Bikes that ran 11s, 10s, 9s and almost 8s. Both foot shift and air shift (air over air and electric over air both). No missed shifts, no problems of any kind.

As Jake says, if its shifting now, enjoy it!