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anyone know offhand how many teeth on the OEM rear sprocket for the 1991 907s?

thanks

40 according to the FAQ here.

Mmmm...if I go to a 37 teeth, anyone done this mod?
You guys think it's worthwhile? How about top end?

The bike has Staintune cans, K&N a/f, and chip.

I'm actually happy with it's performance as is, just considering the sprocket swap.

Thanks!!

Mmmm...if I go to a 37 teeth,

Why, lower revs?

I bought mine w 15/39, felt weak to me.
Now w 14/39 I like it. 5th feels cool until 120km/h, 6 th still an overdrive.
14 is hard to get nowadays so I will probably go 15/41 or 42 next time.
Just my 2c.

I use 15 / 46(!!!) gearing and never go back to normal anymore. Fits much more better to my driving style...

Btw, near all modern Ducatis are geared from factory too low, to meet allkind of noise and emission, etc standarts... Same with original exhaust systems. Its quite rare to see, that someone drive his/her Ducati with normal gearing or with normal exhaust pipes... :laugh: :laugh: :laugh:

Posted: Fri Aug 17, 2007 2:28 pm Post subject:

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I use 15 / 46(!!!) gearing

Ever tried speedway? Think the gearing would work!

Many times...(but too expensive to me, cause after 3 hour driving good tires are ready to change ) and i like drive fastly in twisty roads. I like to use just ALL gears in twisties, where speed is not "so high", like in motorways, which are very boring to Ducaties.... Surely driving style is very important, if thinking gearing. If need to drive fastly in German motorways, then need surely lower gearing. I hate such roads, so thats why i use big rear sprocket.... Btw, 750 Paso gearing dont need so much changes, but 907 and ST4S needs totally different, than OEM sprockets. Sorry, i wanted to say, that ALL ST modells need!!!

Btw, that gearing depends very much about race track. If shorter track, then higher gearing and via versa...

I'm looking to lower the revs when doing 60+ mph so I guess a 42 would be my best bet?

What gearing have you had until now?
If you`ve had less than 42 rear it will rev more at 60 w it.

right now I have the stock, original gearing so I figure if I go with a 42 it should be LESS revs at 60mph for example. Correct?

No. Bigger rear = higher RMP at 60.
42 higher revs than 40.

Stock gearing for 907ie chain wheels is: 15/40

I'm running 14/42 on all my 907ies and prefer it. I went down one tooth in the front and up two in the back.

Since the front chain wheel is smaller, going down one tooth in the front has more impact on power delivery than going up one tooth in the rear. Going from 15 to 14 teeth reduces the circumference of the front chain wheel by almost 7%; increasing the rear chain wheel to 41 teeth only increases rear chain wheel circumference by 2.5%)

http://www.xs4all.nl/~ator0437/gc/

This link is to a gearing calculator.

As usual...great info and help!! much appreciated guys!

My 1992 907ie came with a 40 tooth rear and 15 tooth front, I believe. The 40 is nice easing along for long jaunts at 70 or 80, like intersate highways. But--- it will likely not pull top end speed with the 40 tooth rear. Theoretically gives you more top end speed with the 40, but if it can't attain it, what good is that? I use 42 tooth on both my 907s and it gives better power, easier clutch actuation at take-off, and will pull top end easier. I have used 41 tooth also, but not a lot better than 40.
I say use 42, even though rpm will be a little higher at a given speed. Better for mountain road running....

dp