Yamaha TRX850 Enthusiasts Forum

I want upgrad Gearbox 5th to 6th how ?

My picture trx850 modify.

http://image.ohozaa.com/view2/wOa7BI3M8QBdZD4s

http://image.ohozaa.com/view2/wOa7suC2LMBIAaa3

How modify run speed to 260km/h ?

trx850 year 1996 spec Japan I want modify speed to 260km/h.

If my calculation is correct this equates to 163mph??

Have not heard of a TRX in any spec achieving this but I wish mine could manage it. No more R6's creaming past me on the straights.

No harm in trying though but it may take more than a 6 speed box...........which I doubt is an easy mod. Some info using search on the forum I recall. Uses some YZF750 parts.

Plenty people have looked at this, with no answer yet. I spoke with Qauntime, and he was strugling to nut anything together.
If he cant get it happening, I wouldnt try unless I seen the cluster come out of the cases myself.
I know it can be done, but havn't seen anyone here do it YET.
When you find out, let me know.
Good luck

My picture TRX850 in Thailand.

It`s been done, YZF750 internals and some machining I believe. Try contacting Over racing, how`s your Japanese?

BigAl-TC wrote:Plenty people have looked at this, with no answer yet. I spoke with Qauntime, and he was strugling to nut anything together.
If he cant get it happening, I wouldnt try unless I seen the cluster come out of the cases myself.
I know it can be done, but havn't seen anyone here do it YET.
When you find out, let me know.
Good luck

Bergwerkstatt (huby) who sold me the prog CDI has put in a R6er but it was a pain!!

Mincehead wrote:It`s been done, YZF750 internals and some machining I believe. Try contacting Over racing, how`s your Japanese?

Now I have got some spare crank cases on the bench I may have a look into this if I can find a dirt cheap complete YZF gearbox to play around with.

Ive been researching this from comments made over the years via the search of late and I read something about you may need to machine some new gear selector forks and machine out a part in the case somewhere...

They were in the delivery program of Overracing. In Holland there are now 3 guys with a 6-speed gearbox on there TRX . Tarwetijger has one off them.

cobbadiggabuddyblooo wrote:Ive been researching this from comments made over the years via the search of late and I read something about you may need to machine some new gear selector forks and machine out a part in the case somewhere...

I would have thought that if you do use YZF mainshaft and layshaft plus selector drum then the forks should all line up with the sprockets?

Maybe the difficult bit is squeezing that lot into the TRX upper crankcase. I doubt the casing internal width is the same but assume that the centre spacing of the two shafts is the same as the TRX. If not it sounds really tricky.

Needs a pile of bits to offer up and see what's possible.

Qn for Tarwetijger - is it worthwhile in terms of performance improvement?

Part numbers and more info: viewtopic.php?f=6&t=7872
Part codes with 4FM are YZF750R parts.

misterdimwiddy wrote: Qn for Tarwetijger - is it worthwhile in terms of performance improvement?

The gears are more close together, which is nice for track use. It is just... racier.
With the 5speed box the gears are quite wide.
I'm not so sure about top speed. Could be better, because of the different final ratio. On the other hand, for top speed you just need BHP (and change the sprockets).

Would be interesting to have a tdm and trx cluster on the bench side by side to see if a hybrid of the two is possible. Looking at the ratios, using trx first, tdm second,trx third , tdm fourth and trx fourth and fifth would yield a very nice close ratio six speeder. The tdm shift drum and selectors fit straight in and I am certain the shafts are identical apart from circlip positions and the first gear pinions machined on the layshaft and have the same centre distance. Some repositionung of circlip grooves and narrowing of the trx gears may be necessary, but nothing that couldn't be done on a home lathe. Without actually looking at them side by side I might be talking out my arse but if I seriously wanted a six speeder I would have a closer look.

Hmmm, good call Lenny, although saying that slimmer pinions and more power may shorten life.