2nd Gear slippage

[Martman]

So my project that I have not driven ( it came in parts) was stated to slip out of second gear by the previous owner. I have the engine and trans out and apart, can see no obvious signs of wear, rounding of edges, etc. I'd hate to put it all back together and have any issues, so can anyone volunteer some insight?
I have a copy of Martin Kietsch's manual and he refers to the 2nd and 6th gear mating surface as trouble areas. Any idea how little wear it takes to generate slipping? maybe old age but I'm not seeing any other than a slight brightening of the contact area.
Cheers,

Marten

[steveho]

I would inspect the shift drum and associated shift forks, as wear in these parts stops the 'dogs' from engaging fully, so can jump out again.

[gpaddict]

Look at the shift forks. That's the first spot that will show wear.

[Speed Freak]

Shift forks can also be bent - then you can`t see wear but the gearbox will not work properly.

But if the 2nd gear slips out under load you have to see wear between the 2 (i think it`s 2nd and 6th gear) gear wheels.




On the pictures a YZF600R gearbox with the same problem (as nearly all Yamaha from mid 80`s to ~2000)

[Martman]

Thanks, forks have almost no wear at all, not bent as far as I can tell-all 90 degrees to their shaft, and the gear mating surfaces have nothing like in the photos above - just a little brightening of the contact area contrasting against the original cast finish of the metal. That rounding is very obvious.

[2smoke]

Also check the shift shaft for damage. Its the shaft that runs thru the back of the engine and the shift pedal attaches to it. The opposite end is part of a ratchet system and they wear, crack etc..

[Speed Freak]

Then you can put the Gearbox back into the engine.

The R1 (RN04) has the same Yamaha problem with the 2nd gear and the gearbox doesn`t look like new in my race bike, but it works fine since i have a new clutch, deburred clutch basket and better oil.
The bike didn`t like the castrol oil, since I`m using the cheap "bike supermarket" brand everything works fine.
My opinion in this case - if you can`t see wear either you are blind or the problem is somewhere else (maybe sitting on the bike)

Here pictures form my R1 gearbox:




And here one sign for a bent shift fork:


Here how it looks when the 2nd gear is slipping out (again the YZF600R)


You say the bike came in parts.
Do you know some details about the problem?
Was it "the 2nd gear slipped out after shifting from 1st to 2nd" or was it more "2nd gear slipped out under high load"?
In first case it is mor a problem of clutch operation or the shifting mechanism (from shift pedal to the shifting drum), second case is typical for the damage you can see on the pictures.

[Martman]

Unfortunately the info from the previous owner was from 10 years ago, the last time the bike was ridden. I didn't get any more detail from him, and to him it was a problem. The wear on my gears is less than what depicted in your photos - thanks for posting that. I'm sure I'll get it sorted.