I've heard this can be done to get a close ratio gearbox in the NC29. Anyone out there done this? Is it a straight swap of all gears? or some gears?

Does it make any real difference?

I'm going to start putting my tired engine together, and was wondering if while I had it apart, it might be worth putting the NC30 gearbox in?

Without meaning to sound like a dick , why the hell would you try to do that sort of conversion unless the original box was totally stuffed. ??

The engine needs to come apart for a freshen up anyway.

And....Why not?

Half the reason I race is to tinker with engines.

Do you have the std nc29 gearbox ratios Greg? Some of the upper ratios might be the same as the nc30, but the lower few (at least) will be different.

The nc30 close ratios are a ripper on the track, much better than the rvf one I currently use. The rvf hrc setup recommends using an nc30 gearbox.

I have a spare nc30 gearbox in a box that says '5th gear gone' if you're interested in one to muck around with.

Yeah i'd be keen, PM sent.

Sounds good - I'd be interested in the results if you have a go at it. A nice tall 1st gear always appeals. I have my old NC30 engine with a duff top end in my dads garage......... hmmmmmmmmmmm............

I now have half the answer to my question, thanks to Stickshift.

The primary reduction ratio on the VFR and CBR is identical, as are the gear ratios for 4th, 5th and 6th.

The ratios for 1st 2nd and 3rd are taller on the VFR. So far it's promising, but I won't be 100% till I have Stickshifts old gearbox and my dismantled engine in my hands.

I just love tinkering.

Oh and the reason the VFR is nicer on track than the RVF? The RVF HAS THE SAME ratios as the NC29 from 1 to 6. Further evidence these puppies are probably interchangeable. (I'm sure there are some of you out there who are treating this as old news...)

your almost right, you can't change 1st gear on most gearbox as its part of the shaft. only 2nd and 3rd gear you can change as the rest are the same ratio. the cbr has a shorter 1st gear so it'll be better for take offs, the only downside is that it makes a bit of a jump from 1st to 2nd but the only time that happens is off the line. you can't use the vfr shaft in the cbr as its a different length due to the extra depth of the slipper clutch.

Dan dan dan dan dan. Where were you earlier.

Just discovered this when comparing the dissassembled VFR and CBR gearbox's

lol, i just went through all this a few months back. we got to a stage that we were going to fit the whole slipper clutch which is a fairly major job as the actuator is on the other side of the engine, ie pushes out rather then in. but it was going to be a lot of effort for not much reward as i dont get compression lock ups so we diced not to.