How weak is the FZR transmission/can I improve it?

[drew6]

Hello all,

Finally starting to get my FZR build rolling... I have a bit of a concern about the transmission.

Just how weak is this thing? I read a lot about the second gear issues and the reason I'm rebuilding mine started because the transmission blew up.

What causes it? Bad design or is it because its between 15-20 years old? When they were newer were the transmission problems as common?

I'm concerned I'm going to be putting money into this just to come up with a weak product again...

Has there been anyway show to improve it? IE. will the YZF gear sets fit in?

Thanks

[reelrazor]

ALL bikes have second gear issues.

It is NOT FZR specific.

I'm talking ALL....HD sportsters/ BigTwins, Old BritBikes, all Jap UJMs, about the only ones you wont hear about are old BMW boxers (essentially a car tranny). Hell, troll any bike forum, search "second gear", it's second only to VR failure as a common fault.

THE problem lies in the rider for the most part. People try to 'speed shift' into second on all of them and so the gear dogs take the punishment when their timing is off. Complicating this is the jump over neutral that has to happen

On sportbikes, people try to drag race them from first and slam into second trying to get a gear before the revlimit hits and they they either disengage the clutch too soon, or they don't complete their foot movement so the dogs have to finish under load (or kick out).

It's less about the 15-20 year old design, and more about the 15-20 year old previous owner(s!)


If you are gonna drag, punish the clutch instead and launch in second. Any ground you lose, you will get back when the other guy is shifting 1-2. Clutches are dirt cheap compared to trans repairs.

WHAT? in your transmission 'blew up' ?? Outright trans failure often starts with-and is as simple as- overtightened final drive chains smoking the countershaft output bearing (which allows the shaft to run unaligned-which makes the gears mesh bad..on and on...)


Ohh, and yes, you can have your gears sent out for 'undercutting' of the dogs. The shops that do this will generally ONLY do it to brand new gear sets and you will end up with a much more aggressive transmission, that will be tougher to engage neutral with and will be more demanding of you especially downshifting under load.

[droccm]

^good info, educated me some thanks.

[drew6]

reelrazor,

Really appreciate the reply. I don't normally buy into all the talk you hear about things like this, however, I was being told by so many people about issues and just read too many posts about it that I figured I should ask the question. I figured it most likely had to do with the operator as just about every performance bike you hear about has some sort of major issue according to popular opinion. If you seek you shall find I suppose.

To answer your question: The roller bearing on on the main shaft (left side;chain side) blew up. It ground down the shaft pretty good and I ended up with lots of chunks on the bottom of the case. I did make it home however, but it was an interesting drive to say the lest. She is a tough old girl.

I was looking at sourcing a good used transmission and possibly getting only the second gear undercut. Even possibly getting the whole transmission cryo treated too.

Hopefully that would do it!

[reelrazor]

on the main shaft (left side;chain side) blew up

main shaft? or countershaft?

The one the sprocket is attached to? (counter)

The countershaft is exposed to lateral loading (too tight a chain) and it's output bearing failure is quite common. For the internal mainshaft bearing to fail is;
a) weird

and : b) generally would scream 'lack of adequate lubrication' or 'contaminated lubrication.

"b" should show effects throughout the engine.

[drew6]

Main shaft. I know, I thought it was very weird too... I bought the bike early in the summer knowing it had clutch issues and it had been off the road for a while. I found out the clutch push rod was a) welded to the ball bearing and b) broke about 1/8 of the way down. I also noted there was approx. 0.015-0.020 play in up and down movement on the main shaft while I had the clutch basket off. I replaced the clutch parts and it worked for a a couple months and then it completely failed.

I'll try to grab some pics tomorrow. Interesting stuff really, must have had a faulty bearing as the engine bearings showed no signs of oil starvation. Again, one of the reason I thought I would ask the above question.

[pnbell]

Just to further generalize/support 2nd gear issues: Its not just bikes, its all transmissions. Motorcycle, Cars and Trucks all tend to use 2nd gear more than any other gear; sports cars very commonly have 2nd gear issues.

Good Luck rebuilding. It would probably be cheaper/easier to just replace the whole engine/transmission... But rebuilding is a better learning experience i guess!