XS650 wire wheel question

Gary,
Yes they are able to be fitted with a little work.

Aaargh, did it again...

The front I've never fitted, but I understand it more or less goes straight on...axle size may vary, I'm not sure.

The rear wheel however is able to be fitted with slight modification. The 650 axle is 20mm while the SR's is 17mm. There are a couple of options:

Have the swing arm slots widened to 20mm...evenly of course.

Sleeve the 20mm bearings down to 17mm with 'top hat' style spacers. You need to remove one bearing to do this. You then make (or have made) top hat sleeves to go inside the wheel bearing, inner races, of each bearing that are 17mm ID. Then you have to remove the bearing spacer from between the bearings and make one that is 17mm ID and shorter than the original one by the total of the top hat part of each of the spacers.

This is getting complicated, do you understand my meaning? If you like I can try to do a drawing and send it to you.

Can't remember the axle spacer sizes, however you need to have the wheel in the centre and the countershaft and rear sprockets lined up. A straightedge will assist there. Then measure the gaps and make spacers to suit. This is just a matter of spacing as I recal. On some bikes you need to space the wheel to the centre and then space the rear sprocket out as well. (....the TZ rear wheel in my DCM for example, needed to have the sprocket spaced out 12.5mm...).

The brake arm can be steel or decent aluminium, and if you have a drum brake model then the job is easy. Otherwise you'll need to weld a front anchor point to the bottom of the swing arm.

The drum rear brake is not able to modified to take a disc at all.

There are RD ('76 model) wheel around if you can get them, that have a rear disc as standard. You could fit an alloy rim to one of those. If I remember correctly my mate did this years ago and he had to space out the rear sprocket a bit to line the whole thing up.

I guess that this sounds a bit complicated possibly...howver, I reckon that it is worth the effort to sort out the top hat spacer stuff. You end up with the lighter SR rear axle and no mofification of the swing arm slots...

Hope I haven't confused you too much...

SR

I have never done a direct SR/650 weight comparison, might be interesting, but I think that you are right. Certainly the SR axles are lighter...

In term of a comparison of effectivness, the drums in my mind have always appeared to have been better at braking as well...one in good condition that is. You could always come up with a modern twin piston caliper set up that may be better...I personally like drums better anyway.

I am currently building a retro cafe SR that has 2 Yam R6 4 piston front calipers and wire wheels, and will have a twin piston caliper with a small disc on the rear...that's still in the process however.

I have used a TX750 drum (well whole wheel actually) on my current cafe racer...larger drum for looks, but quite heavy. There's a pic of that one on this site somewhere. There's also an article on it on the Thumper Page.

I have seen people use the upper caliper anchor point for the drums, but it places the backing plate upside down and doesn't look good to me. It is better to weld one on the lower side. You could always try to get a drum brake swing arm...an SR one or maybe another model Yam one would fit as well. I haven't tried that yet. Get an old swing arm, saw off the anchor point clean it up and then weld it straight onto you arm. Saves fabrication. Leave the disc one on in case you change it back some day...

I use a cable actuation on the drums. Easier to route and not hard to make. I weld a cable end-fitting attachment into the backing plate and position a fitting somwhere at the other end to attach to. I have just done this again on my DCM SOS racer using a TZ rear drum.. nice looking unit.

SR

Hi,
Not so sure about the cuch drive on the XS...I know the TX750 rear I have on the CR doesn't have one. There is a benefit to them as a shock absorber for the drive train.

As someone said on the thumper page, the 650 and certainly other bikes that don't have cush drives often have a shock absorbing clutch instead. The SR doesn't have this however. As for long term effects it may increase wear on the gears etc...but to what extent I don't know. It doesn't seem to effect the CR and I have just fitted another non-cush drive rear wheel on the DCM as I said before. I guess to do what I normally do anyway will alleviate any real problems, like moving off down the drive in neutral before I engage the gears when first starting off from cold. You have the clutch for normal riding. Perhaps over a long time transmission/drive train snatch may increase wear....

I'll ask my mate in Adelaide and see what he comes up with. He builds his own classic racing bikes from scratch, engines, suspension and all...and his bikes have won Aus championships. His SR has the same rear wheel as mine. Doesn't bother his, so it doesn't bother me.

Interestingly I have a rear wheel from my DCM that was supposed to be from a 650 Yam...it definitely does have a cush drive. It may be model dependent. I haven't researched that one yet. But I will.

The hub castings have Yamaha written on them, so if it's not from and XS I'll find out what it is from in the long run. It has a electric connector on it for detecting brake cam movement, thus brake wear I guess. I'll get back to you on that one. Not sure what an RD rear drum is like...maybe???

The XT rear wheel is more or less what is fitted to the wire wheeled SR's from the factory. I'm sure I've talked to Devon on the net over the years.

The XT rear wheel should go straight on...details like spacers etc. permitting of course. Axle size is right as I recall. I almost fitted one to mine. Tyre/rim sizes should match for sure. Again not exactly sure of the rim size, but it is easy to find out. The SR rear rim is not very wide anyway, I have fitted 120'S to some of mine, but 110 size is better for handling..try Bridgestone BT45's...excellent grip wet or dry.

I've owned several XT's in my life, I always had large size knobbies on them, at least 4.00, probably larger...

Hope I have helped you. I love these bikes, and have owned 4 of them. I still have 3...fun to ride and to play with..they are almost like a kit bike in my mind...I'd be happy if they sold them new, with no tank, seat, guards, bars etc. Just fit your own...

SR

Great information Stew and a big thank you! A very nice XS650 front is on its way to me, and I've got my eye on an XT rear. I actually like the black rear drum, as my plan was to black out a few odd parts here and there anyway. Thanks again!
Gary
Hopwheels