I recently picked up a 2000 CBR600F4 which is plagued with the "popping out of second gear" issue.

I pulled the engine and split the case to confirm, and sure enough, the dogs are shredded on the two engaging gears on the countershaft for second gear.

These gears are:
GEAR, COUNTERSHAFT SECOND (33T): 23441-MBW-000
GEAR, COUNTERSHAFT SIXTH (26T): 23521-MBW-000

I look these gears up, and they're NLA from anywhere I can find them listed on the web.

Then I look at the F4i's gears, and I see that the equivalent 33T gear is: 23441-MBW-J20, but I can't find any information on whether it fits the F4. I was working under the assumption that it would be close enough, but then noticed that the 26T gear is listed as a 27T gear (23521-MBW-J20) for the F4i. So now I think I need the mating gear to this on the mainshaft as well, but I see zero information on this anywhere on the internet.

This seems to be a very common problem on these bikes but there's no information on how people fix this?
Is there a source for gears I don't know about?
Will a full F4i transmission (or even 600RR transmission - I have an engine I could take them out of) fit the F4, or are there other differences that will stop me?

Thanks


Pics:

33T:


26T:

 

You may want to have second gear back cut before you rebuild the trans. It shouldn't be much but it will likely keep second from blowing again.

 

My current plan is to buy a full F4i transmission from ebay and swap the whole thing if it fits. Waiting on some closeup pics before I pull the trigger.
Some gears/washers/mainshaft/etc are common between F4 and F4i, so I'm hoping the overall dimensions are the same.

If the 2nd gear dogs are bad on that set, I can at least order the two F4i gears (if I did this now, I'm almost sure I'd need to buy the F4i mainshaft 6th gear also, maybe more.)
If it doesn't fit


I've looked into back cutting them, kind of undecided. I could try to get a ~5 degree back cut done, but haven't bothered to ask to see if anyone's willing to do it yet.
Downside is that I may lose a gear if something goes wrong, and I'll potentially be removing whatever surface hardening is on the gears.

 

Back cutting will only insure the trans doesn't disengage a gear and go into a false neutral. I've had this done on many of my bikes with no I'll effects. Good luck but don't scimp on the trans since you have to remove the engine and split the case every time it needs service.

 

I'm still looking at how hard it will be to do them in-house, but the first set of gears apparently lasted 70k, so a new set shouldn't have issues for a while even if I don't

I also still have no source for new gears, so this hinges on me finding a good used F4 pair of gears, or finding a good full F4i gear set.

 

If you are in the states Falacon does great work. I have used them with great results.

 

I can confirm that CBR600RR gears do not work in a CBR600F4.

The spacing between mainshaft and countershaft changed somewhere between F4 and RR. Gears physically fit on the shafts (except 1st gear), but they don't fit back in the case.

Next option is to try F4i gears since they still have gears available.

 

I'm not in the US either, so for sending gears away to get cut, its x1.4 the price, +$100 for me.

 

Perhaps you can find a way to get them hardened? Don't forget new syncros.

 

I received the F4i gearset today. On first glance it looked like it would fit, but it definitely does not.

I still plan to pull the whole gearset apart to clean/oil and get a good look at everything, and I might need to use the F4 mainshaft because the clutch is apparently different between F4 and F4i - otherwise I should be good.

I found some new "Purple" clutches in a bin of RR stuff. Part number is different, but they seem identical after a few quick measurements.
Odd: The F4 doesn't seem to use the thinner "Green" clutch discs as the first and last discs, and has one less plate+disc than the F4i manual shows.