Yamaha xj900f Project

[GRW]

Yes yes, no.
I’m not going there! It’s not like the Kawasaki, where the bevel bit is a bolt on. I know two bevel drives are inefficient, but compared to faffing about with sprockets and chain, give me a shaft any day.
I am interested to read how the handling is affected by various things though - tyre size, wheel inline offset etc.
The decision is made on wheels, it’s tyre that needs pinning down, and I expect to buy one, fit it, measure up, remove if from the wheel for machining, then refit.

The bike I've owned for the last (cor!) 14.5 years... is a shaftie, so I'm with you there (my Rockster runs a 180 rear tyre) - I also had a Kwak GT750 many moons ago for quite a while.
I suspect that the innate difficulties of altering much (due to the shaft drive run and alignment) the drive system is going to dictate your max tyre size - end of.
The issue I think, is that you're not really going to be sure if an oversize tyre will clear the swinger - until you actually fit it and inflate it?
Even then, if its very close, then when you ride the bike any tyre deformation might kibosh what looks great stationary.
Sounds like it'll be a "suck it and see" job.

 

[dobbslc]

But what about getting the better tyres 18 inch isn’t exactly performance category? Whereas 17 inch radials?

This was on a 1984 RD125 back in 1989! I'm not sure they had invented radial tyres back then

 

[minimutly]

I had a look, the wheel is a j17xMT4, the tyre is a 150/70/17, and it overhangs the wheel by quite a bit -albeit it’s a little deflated.so if the wheel is 4 inch or 100mm give or take, could the tyre not be a 130?
So if I go to a 140, that means roughly 5mm per side less overhang - or does it also depend on carcas shape from the manufacturer? 5mm less might just be enough, I would like more, but the issue is always going to be the tyre side rubbing the shaft side if the swingarm, unless I space the wheel the other way, and really butcher the swingarm to move it across even more, which of course means moving the whole engine across to match.

 

[GRW]

I had a look, the wheel is a j17xMT4, the tyre is a 150/70/17, and it overhangs the wheel by quite a bit -albeit it’s a little deflated.so if the wheel is 4 inch or 100mm give or take, could the tyre not be a 130?

No. If its a 150 on the sidewall then it's a 150. But that is mitigated in terms of actual width by the construction, shape and the sidewall of the tyre (as well as the tyre rim - e.g. a narrower rim tends to make a tyre "balloon" shape a bit more than a wider rim where the sidewall is more vertical).
You could fit 2 different designs of 150 tyre, and one might clear while the other didn't.

 

[GRW]

Google "motorcycle tyre measurements explained"
(For some reason I can't paste in a linky)

 

[Fastdruid]

A 130 is too narrow for a 4in rim. 140 is the narrowest you should fit.

 

[minimutly]

No. If its a 150 on the sidewall then it's a 150. But that is mitigated in terms of actual width by the construction, shape and the sidewall of the tyre (as well as the tyre rim - e.g. a narrower rim tends to make a tyre "balloon" shape a bit more than a wider rim where the sidewall is more vertical).
You could fit 2 different designs of 150 tyre, and one might clear while the other didn't.

Bad grammar on my part - what I meant was if the wheel is 100mm could I not fit a 130 tyre? I’ll have a google, thanks.

 

[Fastdruid]

Bad grammar on my part - what I meant was if the wheel is 100mm could I not fit a 130 tyre? I’ll have a google, thanks.

At the risk of repeating myself. No. The narrowest on that rim should be a 140.

 

[minimutly]

Bah, that told me nothing, other than you should only fit the width of tyre the wheel is designed for....
Yeah, but what is that?
I have learnt something though, I know now why my old xj650 with narrow wheels (especially front) is so unstable.
More googling needed...

 

[minimutly]

At the risk of repeating myself. No. The narrowest on that rim should be a 140.

Ok, I hear you, but where did you get that from? Is this experience, or lord help us, is there a chart from the manufacturers, because I can’t find one with 4 inch rims on it?

 

[GRW]

Bah, that told me nothing, other than you should only fit the width of tyre the wheel is designed for....
Yeah, but what is that?
I have learnt something though, I know now why my old xj650 with narrow wheels (especially front) is so unstable.
More googling needed...

I've only ridden an XJ650 once - and it was a bit of an old shonker (think it was an '82 bike some 20-years on).
I didn't find it unstable (it's quite a long bike)... OK it wasn't super-stable at 3-figures, but I put that down to its tired chassis.
Biggest shocker was just how flat and gutless it felt for a 650 - and how peaky and lacking in mid-range for a middleweight it was.
I lusted after one as a teen - it kinda blew my bubble.
I guess it highlighted the quantum leap bikes made in just a few short years, as my 87 FZ750 was vastly better (mind you, my 83 GT750 was rather better also).

 

[minimutly]

Mmmm, they’re not known for being gutless - on a par with other two valve engines of that era I would say. My maxim is 30,000km, jap import, and as tight as when it was made engine wise. Low speed I would say it feels “light” if that makes sense? It’s nice to poodle about on a sunny day, but a performance bike it never was.

 

[Fastdruid]

Ok, I hear you, but where did you get that from? Is this experience, or lord help us, is there a chart from the manufacturers, because I can’t find one with 4 inch rims on it?

Tire/Wheel Fitment

Use this table to determine the tire size that can fit your rim. Front Wheel 16" Tire Size Rim (inch) 110/90-16 2.15 - 3.00 120/80-16 2.50 - 3.00 130/70-16 3.50 - 4.00 130/90-16 2.50 - 3.50 150/80-16 3.00 - 4.00 17" Tire Size Rim (inch) 110/70-17 3.00 - 3.50 110/80-17 2.15 - 3.00 120/60-17 3.50...

ridewrightwheels.com

 

[GRW]

Mmmm, they’re not known for being gutless - on a par with other two valve engines of that era I would say. My maxim is 30,000km, jap import, and as tight as when it was made engine wise. Low speed I would say it feels “light” if that makes sense? It’s nice to poodle about on a sunny day, but a performance bike it never was.View attachment 336969View attachment 336970

Whdn a new model they were praised for many positive traits, but even then I recall testers stating that the motor was very lacking in midrange and the need to rev the thing to make progress.... sort of a 650 with a powerband like a 250 stroker.
That's exactly how the one I rode (admittedly old) - it needed revving hard to make progress, and letting the revs drop made it breathless and stodgy, and in need of a lot of gear lever tap dancing for a 650. Maybe the aftermarket 4-1 pipe exacerbated it on the one I rode, but I found the motor very under-whelming - like Yamaha had sacrificed way too much drivability in the quest for a peak bhp figure.
I think ridden as you say - pootling on - it's probably a nice ride. I suppose with all the bikes I've owned post the FZ750 being 1100, 1300 & 1150cc, the big mid-range hole and lack of torque of the XJ650 just didn't suit me.

 

[minimutly]

Tire/Wheel Fitment

Use this table to determine the tire size that can fit your rim. Front Wheel 16" Tire Size Rim (inch) 110/90-16 2.15 - 3.00 120/80-16 2.50 - 3.00 130/70-16 3.50 - 4.00 130/90-16 2.50 - 3.50 150/80-16 3.00 - 4.00 17" Tire Size Rim (inch) 110/70-17 3.00 - 3.50 110/80-17 2.15 - 3.00 120/60-17 3.50...

ridewrightwheels.com

Thanks, I looked hard for something as comprehensive as that.

 

[minimutly]

Whdn a new model they were praised for many positive traits, but even then I recall testers stating that the motor was very lacking in midrange and the need to rev the thing to make progress.... sort of a 650 with a powerband like a 250 stroker.
That's exactly how the one I rode (admittedly old) - it needed revving hard to make progress, and letting the revs drop made it breathless and stodgy, and in need of a lot of gear lever tap dancing for a 650. Maybe the aftermarket 4-1 pipe exacerbated it on the one I rode, but I found the motor very under-whelming - like Yamaha had sacrificed way too much drivability in the quest for a peak bhp figure.
I think ridden as you say - pootling on - it's probably a nice ride. I suppose with all the bikes I've owned post the FZ750 being 1100, 1300 & 1150cc, the big mid-range hole and lack of torque of the XJ650 just didn't suit me.

Hopefully the 900, built in the seca style, with bigger engine and stickier tyres will be an improvement. I have some Ikon adjustables for the rear and expect to fit some cartridge inserts in the front tubes. Whatever, it’s a time consuming but cheap project, maybe...
I’m at a bit of a disadvantage because of my limited bike experience - the vmax is a bit of a monster, but it has 3 wheels.

 

[GRW]

Hopefully the 900, built in the seca style, with bigger engine and stickier tyres will be an improvement. I have some Ikon adjustables for the rear and expect to fit some cartridge inserts in the front tubes. Whatever, it’s a time consuming but cheap project, maybe...
I’m at a bit of a disadvantage because of my limited bike experience - the vmax is a bit of a monster, but it has 3 wheels.

For sure I think the 900, tuned as a usable roadster/tourer/workhorse, should be a far nicer engine to use on the road, with much better torque, midrange and the delivery where you need it to be.
I've ridden a 2-wheel V-Max - and it's actually a nice engine and very usable - people focused on the 145bhp number, but it's pretty docile unless you're a ham-fisted maniac.
I had an X11 Honda that in real terms would annihilate a V-Max, but again it was only a hairy-arsed thing if you were aggressive with it.
On the road, mostly you want a usable, progressive bottom & mid-range that let's you lug a decent gear but responds neatly when you ask for it (IMO). A large capacity, sensibly-tuned motor fits the bill. I can see the XJ9 doing the job without being intimidating

 

[magicgrotto]

Pics would be nice so I can get my head around wot your trying to do LOL & IF the pics that have been put up are the bike ? then a xs1100 wheel will NOT fit

 

[minimutly]

Pics would be nice so I can get my head around wot your trying to do LOL & IF the pics that have been put up are the bike ? then a xs1100 wheel will NOT fit

No, the pics above are of my two 650xj's. The 900f is a beefier frame, similar suspension etc.
So I'm using a seca tank, making seca copy sidepanels to fit the frame, 900s wheels and brakes. So it will look like the 650 seca (the one with the blue tank), but should go, stop and handle much better.
Can't do pics - its buried under stuff.