xt 600 gearbox

[petertriumph]

hello. Just bought a gearbox for my 1vj . I don't know the origins of the new box, apart thats its in great condition! It has 2KF on the selector drum, and 4PT on each of the selector forks. Its identical to the 1vj to look at, has the same amount of teeth on the cogs,the same shaft diameters and lengths. I've slotted it in the cases and it seem to function fine. Would be grateful for any ideas.
Thanks,
Peter

[aukeboss]

Then you have a good gearbox! The 4PT would indicate to me that it is from a later model XT600 - which is good because it has the latest version of cogs in Yamaha's neverending quest to solve the gearboxproblem with the XTs.

Ride ...

[kenymact]

As long as there is no pitting on the gear teeth it will be fine,the later xt s suffered from fifth gear failure.....

[aukeboss]

@ kenymact:
It's the earlier XTs that suffer most from the pitting issue.
Yamaha has taken several measures over the years to at least reduce the problem:
- Shorter final drive; on the Teneres the final drive went from 15-40 to 15-45, for example
- Additional oil line direct from filter to gearbox, feeding colder oil to the gb
- Modified cogs

So, if you are looking for less gb problems, the newer your model the better.

A

[petertriumph]

Thats good news ! Thanks. But will it fit into my bike? It looks identical - but I've heard rumours that they aren't compatible.
The fith gear has very faint signs of pitting. Is it worth changing now its apart, and if so must I change both fith gears - the other one looks perfect!

[aukeboss]

If it fits in physically, the shafts have no excessive play and it changes and turns well in all the gears, it will work well.
It might be that the rumour you refer to is caused by the fact that the later XT6s had a 17" rear wheel, and the primary transmission (gears on crankshaft and clutch) was changed for that.
You say the number of teeth on all the gears are identical to those on the 1VJ gb, so the transmission ratios are the same if you keep using the 1VJ crankshaft cog and clutch.

Change fifth gear: I'd advise to do that, only change the damaged cog.

A

[petertriumph]

More good news!
Thanks for the advise Auke.
Peter.

[kenymact]

My 2002 5th gear went and I would recommend changing them as a pair, the 5th gear problem is highlighted by ex rental bikes ,fully loaded sometimes with a passenger the rental guy would change gear at too low an rpm and it would hammer the gear causing the pitting...