Yamaha TRX850 Enthusiasts Forum

I'm getting close to finishing my project bike now but need some help with the front sprocket.

I've fitted at YZF750 swingarm and wheel (180 rear tyre). I'm using a TRX850 rear sprocket and TRX chain, but it looks like I need a front sprocket that's offset by about 6mm to get it all to line up.

Questions:

1) does anyone know if is there a standard sprocket from another yamaha that has the necessary offset which will fit on the TRX output shaft?
2) is there a UK based engineering firm that can machine a special sprocket?
3) does anyone have any experience with fabricating an offset sprocket by welding the offset outer toothed part of the sprocket onto the splined inner part?

All advice gratefully recieved!

If you are using a standard trx rear sprocket with a 'dished' side to it, if you flip it over so the dished side is on the inside, this may move it over enough (4 or 5 mm) to line it up with the standard front sprocket in its standard position and the chain still miss the tyre (just). Worth a go.

Otherwise, get a few of the front sprocket washers and put them on the front shaft before putting the sprocket and nut on maybe??

trixynut wrote:If you are using a standard trx rear sprocket with a 'dished' side to it, if you flip it over so the dished side is on the inside, this may move it over enough (4 or 5 mm) to line it up with the standard front sprocket in its standard position and the chain still miss the tyre (just). Worth a go.

Otherwise, get a few of the front sprocket washers and put them on the front shaft before putting the sprocket and nut on maybe??

I wouldn't go down the latter route From memory, the nut is machined to both torqued up against the nut AND the end of the shaft

dandywarhol wrote:I wouldn't go down the latter route From memory, the nut is machined to both torqued up against the nut AND the end of the shaft

DW is right - I wouldn't do that either

You could just machine 6mm off the rear wheel

Terzikat wrote:I'm getting close to finishing my project bike now but need some help with the front sprocket.

I've fitted at YZF750 swingarm and wheel (180 rear tyre). I'm using a TRX850 rear sprocket and TRX chain, but it looks like I need a front sprocket that's offset by about 6mm to get it all to line up.

Questions:

1) does anyone know if is there a standard sprocket from another yamaha that has the necessary offset which will fit on the TRX output shaft?
2) is there a UK based engineering firm that can machine a special sprocket?
3) does anyone have any experience with fabricating an offset sprocket by welding the offset outer toothed part of the sprocket onto the splined inner part?

All advice gratefully recieved!

I used a Raptor 660 (quad) front sprocket with a 3mm spacer behind it to offset it enough to clear the chain. The Raptor sprocket isn't shouldered like the TRX one so can be moved out and still leave enough room to fit the locking washer. I did a 520 conversion though.

Or you can try contacting Talon Engineering- they do custom sprockets to order and should be able to make up a suitable sprocket pretty quickly as the spline pattern is common to loads of bikes.

Send them this-



and tell them how far you want the offset to be

But is the shoulder not there for the reason I mentioned above?

There's been instances of TDM sprockets coming loose and damaging the threads beyond repair by careless fitting and using the wrong parts - and relying on the locktab to do all the work!

dandywarhol wrote:But is the shoulder not there for the reason I mentioned above?

I don't know, but surely if the (total width of the Raptor sprocket + spacer) = (width of standard sprocket) then there is no issue?

Hmmmm, should be - as long as there's space for the locktab to fit just flush on the end of the splines...................

Thanks for the info

I don't fancy the idea of flipping the TRX rear sprocket around to move it further inboard as I want both sprockets and the chain to line up with the plastic chain guide that goes over the swingarm pivot. I might even need to pack the rear sprocket outboard a fraction as the TRX chain is a narrow gauge than the YZF one.

The raptor sprocket sounds good though - I'll have a look at that.

Cheers

I got a new sprocket in 520, and turned the teeth off my old sprocket. It was old and worn out anyway. Turned it right down so it was just a washer basically. Welded the 2 sprockets together. Then bored out one side a bit so the nut would tighten up properly. I also turned the rear sprocket around to get a few mm saving there.

I used to run a 190 tyre and it was the best way i could get it to fit.