Hi Bugs,

Been watching your thread as i'm also busy with a gearbox.

After much research i have yet to find a well documented post on what is possible to extend the life of the transmission, especially 5th gear. There are many threads but little specific, no part numbers and often the final solution to a thread is not posted!

No doubt Yamaha have a system that traces when and where changes take place and where they are applied, i've yet to find it. That the prefix is taken from the 1st bike to use the part is inconsistent and, what about all the non-prefixed numbers? :confused1:

I'll share what i've found, certainly not conclusive as this is my first XT, and from other posts and manuals, this is what it looks like:

Predominant troubles posted are short 5th gear life, oil pump damage from tooth debris leading to piston failure, lack of lubrication.

Early bikes had carry-over gears and oil pump from XT550, 5Y1 and 'splash' lubrication.

4 mods were done:
better gears
better lubrication
pressure fed lubrication
2nd upgrade to gears

1VJ got the 1st upgrade to some gears and a larger oil pump, 6mm. Also, maybe oil jets inside the case, fed from low pressure side of oil pump. These jets can be seen in both sides of the case fed from return line to tank via a gallery over the gears. My '87-'89 2kf has them.

Possibly the next change was an external oil pipe from the pressure side of the pump to oil jets over the gears. The oil pump was again enlarged, now to 8mm.

This was applied to 2nd version of 3AJ, 1989? There is evidence the black cases did not have the pipe and the silver cases did.

The next upgrade may have taken place after 3AJ. The 2JT 5th gears were used in the 600e, but are now what we should use. Ask for them or you may get 1VJ like i have.

In fact i believe one can order gears off the 3TB lists, the gears probably remain the same to the end of 600e. The output shaft is too long for a kick only bike but may fit an earlier e start. The output for early bikes (2 bolt) is obsolete but the 2kf one (fine spline, nut and lockwasher) should fit kick versions.

A final mod was made which i believe only happened on e bikes but may be able to be used: The ratio between enging output and clutch was changed to run the transmission at a higher speed thereby reducing torque load. Requires a lot of parts to change, including different sprocket ratio. Am not an engineer but not convinced this does any good.

Everything before it does.

I don't think 34L, 43F or 55w will have the jets cast in. Some fine engineering will need to be done if not.

It would be useful if those who have cases open to post your findings and model, or add your knowledge so we can build a good database once and for all.

My '88? 2kf does not have the external pipe but does have a cast 'knob' on the right hand case over the gallery mentioned earlier. I will be able to add the pipe by some careful drilling and tapping. The gallery will need to be blocked right at the clutch actuating shaft end to separate the 2 oil supplies.

It would be useful if those who have cases open to post your findings and model, or add your knowledge so we can build a good database once and for all.

I hope this does not sound too technical. I know a few pics would help. Prob is my smugmug learners has expired and i've yet to dicover the rules around a smug account and what happens if you stop paying?

I welcome all contributions, am happy to post the results to a popular forum.

Thanks,
p