Taller Gears

[babyblueblade]

Hi All,
I'm pretty new to the race bike scene and have just bought a CBR 400 NC29 1990. I have the feeling that the gears are very close together and by that I mean there doesn't seem to be a great deal of difference between the gears and I sometimes wonder whether I have changed gear at all (but know that I have either by opening it up fully and when changing down)! Could someone advise me to how many teeth there should be on the sprockets and whether if by changing the amount of teeth the gears would become taller? Sorry if this all sounds a bit dumb!
Regards Rano.

[justmartyn]

From what you're describing it sounds very like the bike has a small front/large rear sprocket combination going on, which will give good acceleration but crap top end. This will make you feel the gear ratios are close together.
From memory I think you should be looking around the 14/42 teeth mark as a fairly standard set up.
Another rule of thumb for your own reference is to divide the amount of rear teeth by the number of front teeth, which gives your final drive ratio. 1:3 (or 3:1 if you prefer) in the case of the 14/42 sprockets. The higher the number the better the aceleration and less top speed.
Could be wrong about 14/42 being standard but its my default setting on my race bike when I havent a clue what I need for a specific track, then I adjust from there.
Hope that helps.

[jetblack]

If you decrease the size of the front sprocket the bike will acclerate quicker but run out of steam quicker- the same is true of going bigger on the rear sprocket.

The reverse causes,well, the reverse!

I beleive your bike came as standard with a 15 tooth front sprocket and a 39 tooth rear so go and have a look at what you've got on there at the mo.

[justmartyn]

There you go then, 15/39 as standard, I stand corrected, giving you 1:2.6. My guess is if its a track bike someone has been swapping them around. Let us know what you find.

[babyblueblade]

Hi again, thanks for your responses. I have only been able to count the rear sprocket which seems to have 40 teeth. I'm not sure what is entailed with the removal of the front sprocket casing as I believe the speedo cable enters through it?. I intend to get a hayes manual real soon and will let you know just as soon as I get some idea of what I'm doing. Sorry if my inexperience is annoying!!

[tanuki]

There are 2 Allan bolts on the speedo drive (the black thing the cable sticks out of) remove that then remove the plastic cover (3 bolts iirc) then give the sprocket a wipe with some wd40 and a rag and you should be able to see stamped into it the amount of teeth, the rear is the same btw it's stamped onto the sprocket.

[babyblueblade]

Hi, firstly thanks for all you comments thus far interesting and informative!! I have checked the front sprocket and found it to be 15T and I am pretty sure the rear is 40T. I would appreciate any further info/suggestions but am aware that there may not be a lot that can be done and it might just be a case of getting used to a new gearing set up as I haven't had the bike that long! Thanks.