YZF 750 gearbox....

[Killerwhale]

....can it be fittet at all?? I think the over got that one eh?
But are there a lot of mods needed in that case??

Cheers

Well, there are a thunderpussy in the gear ratio program so....

Here we go:
TRX: 36/14, 37/20, 30/21, 27/23, 28/27 - 17/39 original
Pussy: 37/13, 37/14, 34/22, 28/21, 25/21, 29/27 - 15/47 original

What do you expert get out of this??
T-pussy and the 750 should be quite similar?!

[HansJ]

....can it be fittet at all?? I think the over got that one eh?
But are there a lot of mods needed in that case??

Cheers

I think You can fit it fairly easy, but questtion is why? I was thinking of it a long time ago, but decided it wasn't worth it. Reason as I recall it was that the gear ratios was not what I wanted, i.e. 6th was pretty much the same as our 5th, and the 1st should be shorter. But I am sure someone will fill in if I recall it wrong. If the 6th could have been more of an overdrive, then it would be more useful, giving the possibility to go up a couple of extra teeth on the rear

[Kevtrx849]

Yup you got it right Hans. Final drive remains the same, it's just the first couple of cogs that were lowered to get it off the line better.
CYA, Kev.

[Max]

I heard it requires a bit of machining in the cases, but I could be wrong (probably am...).

It could use an extra cog between 3rd and 4th (with 4th a bit closer to 5th..). That's the only place it was hurting on the track I raced at, especially with a tight right coming onto the straight with an uphill. I had to take it off the scale in third so 4th wouldn't 'bog' on the hill.

On the positive side, a five speed is more durable.

[Killerwhale]

....can it be fittet at all?? I think the over got that one eh?
But are there a lot of mods needed in that case??

Cheers

I think You can fit it fairly easy, but questtion is why? I was thinking of it a long time ago, but decided it wasn't worth it. Reason as I recall it was that the gear ratios was not what I wanted, i.e. 6th was pretty much the same as our 5th, and the 1st should be shorter. But I am sure someone will fill in if I recall it wrong. If the 6th could have been more of an overdrive, then it would be more useful, giving the possibility to go up a couple of extra teeth on the rear

Well, i think my bike would be quite OK in city traffic with 16/42 something...with a lower first i could use standard...
I also think the revs drop to much between 2 & 3 to then even out between 3 & 4 and dont drop at all between 4 & 5th
I dont think its as even as i want it, thats all!

...then it would be nice to get away from the CLUNK when going from 1 to 2nd.....

Also...was the YZF really geared 17/39??

[phuk72]

AFAIK ...

No, a YZF box doesn't fit straight in.

Over made their own 6 speed box - it wasn't a YZF box.

First 5 ratios on the YZF box are broadly similar to the TRX box so if the mod were to be made you could piss about with final drive gearing and use 6th as an overdrive.

[Max]

I don't know what OVER did, but I do know there were quite a few racers using the YZF transmission over here. Again, I think it required some case mods. Also, YEC made a CR cluster for the YZF.

[honkdawillydahonk]

AFAIK ...

No, a YZF box doesn't fit straight in.

Over made their own 6 speed box - it wasn't a YZF box.

First 5 ratios on the YZF box are broadly similar to the TRX box so if the mod were to be made you could piss about with final drive gearing and use 6th as an overdrive.

I thought 1st and 5th were equilvalent to 1st and 6th on the YZF (I will check though) so all you gain is closer ratios in between....

[phuk72]

I thought 1st and 5th were equilvalent to 1st and 6th on the YZF (I will check though) so all you gain is closer ratios in between....

That makes more sense (not that I'ms saying you're right you understand )

[wicky]

wasn't there a guy on here or the old site that modded a TRX motor by fitting 900 barrells/pistons and a YZF gearbox with TDM 900 ratios ?? twas fer sale on ebay a few weeks back.

[wicky]

ahhh heres the link, most of you folks prolly know the owner/builder so sorry if this has already been posted up here somewhere already. s'definately a 6 speeder too as i asked him a fair few questions bout it.


http://cgi.ebay.co.uk/YAMAHA-TRX-900-SP ... dZViewItem

[phuk72]

A YZF gearbox with TDM ratios - are you sure he had just used the bottom end of a TDM900?

[Killerwhale]

....can it be fittet at all?? I think the over got that one eh?
But are there a lot of mods needed in that case??

Over got the YZF 750 as i thought.....

http://www.motorcycle.com/mo/mctext/over.html

[wicky]

A YZF gearbox with TDM ratios - are you sure he had just used the bottom end of a TDM900?

dunno man, i did have some emails he sent me about what he did/used etc etc but me PC went tits up last week and i lost em all !! thing is it looks like a TRX/TDM 850 borrum end to me ??? read the questions at the bottom of his advert. Citroen54 from the old TRX site say's he had come across this seller on that site and seemed to know his onions in his opinion. just seems like alorra hassle fer 6 gears if ya ask me, then again it's prolly a hobby/goal fer the builder.


ps just looked at the pics again and im wrong, thats definately a 900 bottom end, looks like he has used an 850 casing on one side but if you look at the udder side you will see the engine finish looks the same on the barrels and the crank casing, so he must have done the gearbox mods he mentioned

[CULater]

That's not a 900 engine on those pictures.
So dunno what he's selling

This is how a 900 engine looks !