[brooksie]

I see here that alot of folks go from the stock 15T counter shaft sprocket to a 14T sprocket. I understand that this gives the bike more off the line grunt, slightly. I feel like, on my bike, first gear seems very short as it is. Is the use of this 14T sprocket more for the 2nd & 3rd ratios? Also, has anyone gone with a 16 or 17T sprocket? The bike just seems like it has plenty to handle one or two more teeth up front in first and second gear. What are your thoughts?

 

[MajorSoftie]

Are you sure you still have stock gearing?

You're right that the bike has plenty of power to handle the stock gearing, but most people find that low-speed operation (like parking lots) requires a lot of clutch slipping, and such operation is much easier with a little lower gearing. This would be WAY worse with higher gearing and very hard on your clutch.

I don't know that there is room for a 16T, and I'm pretty sure there's no way a 17T would fit in there. If you COULD run a 17T, these would be your 8500 rpm speeds in each gear:

1: 60 mph
2: 83.8 mph
3: 109.6 mph
4: 135.6 mph
5: 154.3 mph
6: 172.6 mph

So, your bike wouldn't even be able to pull 5th gear to redline, and 6th would be a pretty ridiculous overdrive going 103.5 mph at 5100 rpm. That gearing would be very close to what you would want for a bike with twice the HP of yours.

 

[brooksie]

Major-great info, thanks! I know when I put the 904 in my Bonnie I went from 17 to 19 and it pulled like a banchee in all gears. It just seemed so much easier on that bike to give the engine some extra time in first gear. The GT pulls as hard, actually harder, as that 904 but the revs are so quick and smooth it is deceptive to the seat of the pants. It gets to the ton in a hurry. I can see that it probably won't be a smart move to go up one tooth with your detailed info and help. Thanks a lot!!!

 

[MajorSoftie]

I should have included this:

This is where I got those numbers: http://www.gearingcommander.com/

You can plug in different bikes and then try all kinds of gearing changes and see what the results will be. I just tried your Bonnie, and changing from 17 to 19 only raised your top speed from 114.1 to 127.6. Obviously the Bonnie has a VERY different transmission from the GT.

 

[Bly]

I see here that alot of folks go from the stock 15T counter shaft sprocket to a 14T sprocket. I understand that this gives the bike more off the line grunt, slightly. I feel like, on my bike, first gear seems very short as it is. Is the use of this 14T sprocket more for the 2nd & 3rd ratios? Also, has anyone gone with a 16 or 17T sprocket? The bike just seems like it has plenty to handle one or two more teeth up front in first and second gear. What are your thoughts?

I ran stock gearing for 12 months or so as I was unconvinced of the need for lower gearing. The engine has so much torque it's not really a problem.
After reading people singing the praises of shortening the gearing I relented and am now a convert. I can actually cruise in 6th now, and rollon acceleration is improved right through the range. Wheelies better from the lights too.
Sure you row through the gears a bit more, but it's such a sweet gearbox I don't find that a problem at all.

 

[brooksie]

Major-thanks for the link. Cool stuff. Here I thought you were some sort of gearing savant!
Bly-sounds like something worth trying. Kinda sums up the results nicely. Gonna give it a go. Thanks!