Hey guys, and gals,
I have a 1998 Honda CBR900RR, and I just got it a month or so back. I absolutely love it. I promised myself that I will never be without a bike ever again, its just too much fun, everything about riding, I love it. Now, to my question. My buddy put a different sprocket on it, for more low end , wheelies, racing ,etc. I really like the acceleration, but I want more top end. It gets up to redline in 6th so fast, and I want to be able to do 190 or 200mph lol. I dont know if that is realistic, but I think it has the power easy. So, how can I find a sprocket that will give me that rpm in 6th that I need. Also, one more reason is that I want to be at a lower rpm when just riding on the highway. At around 90 or so on the speedo I am pushing close to 6,000 and I would like to get that down for mileage and stuff. So, any ideas on info would be much appreciated. I know someone will ask how many teeth are on the sprocket I have, but I havent counted so I dont know. Even a little more would be good, and getting back 1-2,000 rpm in 6th while cruising would be great. Thanks in advance and I am so glad I found this forum. L8R

 

the teeth count is written on the sprocket - generally

going back to stock is a good idea - and don't worry about 200mph

 

well, I did a little research. its supposed to be 16 front and 43 back stock. It looks like it says 45 on the rear sprocket and I am assuming the front was left stock. I was thinking of going with a 17 front and a 40 rear. What do you guys think, will I lose much that it will be noticeable? I want to lower my hwy rpms at 75-80 since that is my usual cruising speed. But, like any other guy, I want to be able to haul *** when its time. I ride with a 00 rc51 and a 750 katana (I can blow the katana out of the water) and want to be able to hold my own. Just wondering if that will be a huge difference in how the bike pulls at full open throttle. Thanks in advance!

 

The math is pretty simple -- divide front by the rear to get the ratio of each setup --- then get the ratio of pair 1 vs 2

quick example with easy numbers:

SETUP A: front 2 rear 4 === 0.5

SETUP B: front 4 rear 4 === 1


0.5 / 1 = .5 whihc is the same thing as 50% --- the first one would have a 50% less speed than the second one.

A is shorter than B

so you have now: 17 / 45 = 0.3778

you want 17 / 40 = .425

= .425 / .3778 ==== 1.125 --- a gain of 12.5 %

Where gears are around 1500 rpm apart -- 12.5% is about gaining another gear...

The next question is - does that setup physically work on the bike.

 

Well, I did a little looking and wrote some people, and they do sell a 17 for the front and a 40 for the back. I of course would need a new chain too probably. Based of your math and another site where you can punch in numbers and figure it all out, I think it would be a good set up for highway cruising. I just dont want it to be a dog in first gear, even though I doubt it will. Thats really my only concern, will it really affect the performance.

 

I went up 2 teeth on the rear on my 99, It has a little more acceleration. My top speed is still the same at 187 MPH, Of course you must take into account speedometer error
My final drive ratio is .355 I am running 16/45

 

With the stock gearing the bikes max top speed is around 160 at best.

Gearing it for 190+ , if it would even get up there (prob not) , would make it a serious dog around town IMO. And theres where it's most fun.

I'd put it back to stock and see how you like that and then fine tune from there.

 

IMO it would be a total dog with the 17/40 gearing. It wouldn't have the torque to pull to a higher mph with that gearing. I'm with whoever suggested going back to stock and see how you like it. Then make subtle changes til it suits your needs.

 

If you go to the Gearing Commander website and load your bike's stock values from the drop-down menu you can play with the numbers for different gear combinations. It defaults to kph so be sure and change it to mph if that's what you want.

Anyway, you're correct. It says that the stock setup is 16/43, with a top speed of 167.6 mph in 6th gear at 10,500 rpm. If you were to go 17/40, as you are talking about doing, the top speed in the same gear at the same rpm would be 191.5 mph, assuming it had the hp to push it that fast.

Let me put it another way. You said that you wanted lower rpm on the highway. With the stock setup of 16/43 you're doing 4384 rpm at 70 mph. With the 17/40 setup you'd be doing 3838 rpm at the same speed.

Hope that helps.