Need help from someone with a set of mags

[bradshaw106]

I'm trying to figure sprocket spacing on my tracker project.. Im using a different swing arm and wheel. So what I need is for someone with a set of mags to take a measurement from the casting mark on the wheel to the back side of the sprocket or the back side of the chain.
Any help would be great.

 

[bradshaw106]

Some one with a set of mags must be able to grab a quick measurement.....

 

[RFLIVES]

I have the omars kit on a 19" mag wheel. But from the inside of the sprocket to a "spoke" on the wheel in 56mm

 

[Q Tip]

My disc rear mag is off my bike but from the face of the rubber seal on the sprocket side to the face of the rubber seal on the rotor side is right at 6 inches. From the face of the seal on the rotor side to the furthest (outside) edge of the cast wheel hub (no sprocket in place) is right at 6 and 1/4".

ok if i am figuring this right you need the measurement from the spoke flat (where it is cast "suitable for tubless tires") to the inside edge of the sprocket? That is 3 and a fat 1/8th on my wheel. That is measured to the flats where the sprocket mounts.

 

[bradshaw106]

What I'm not sure about is whether the brake rotor and sprocket are the same distance from center? On a cb750 the sprocket is much further out then the rotor. So I don't think we can take that measurement and split in half?..

 

[Q Tip]

ok from the web of the spoke casting (where the "suitable for tubeless tires" and similar stampings are) to the sprocket seats on the hub is 3 and 3/16ths. From the web of the casting on the ROTOR side to the rotor seats on the hub is 2 and 1/2. the thickness of the web on the spokes seems to vary from between .240 to .300 depending on where/how you measure.

So they appear to be offset with the sprocket side distance about 7/16ths wider.

 

[bradshaw106]

That's what I'm looking for. What do you mean by sprocket seats?

 

[1974jh5]

On the SR500 wheel I used on my bike, the sprocket side projects further from center than the rotor side. Sorry, I don't know exactly how much.

I centered the rear wheel in the bike by putting the frame on a stand and making sure it was level side to side, Harbor Freight sells a digital level for ~$30 that was invaluable in getting that part done. I then tied a string to the steering neck, making sure it had a 'V' in the loop so it would self center and ran it to the rear of the bike, draping it over the fender hoop. I put a plumb bob on that end to keep it taut. I then used a very long 6mm thread bolt in the rear fuel tank mount which was maybe 1/8" under my string and moved the string until it was centered over that bolt. That gave me the frame centerline. I measured the rim width and marked it with a center punch so I'd know the exact centerline, put the wheel on the axle, then put it under the plumb bob and slid it side to side till it was centered, then took my measurements. I had to turn .400 (almost exactly 7/16") off of the sprocket side spacer and then make a similar spacer for the rotor side to keep things centered (basically scooted the wheel .400 to the left). Once the wheel was centered, the sprockets lined up perfectly.

 

[Q Tip]

That's what I'm looking for. What do you mean by sprocket seats?

the part of the hub casting where the sprocket bolts onto. Or, on the other side, where the rotor is bolted on. The flat surfaces of the mounting pads, or seats.

Don't know what the real term is.

Basically it equals the backside or inner side of the rotor or sprocket.

All measurements were made with a tape measure and eyecrometers

 

[bradshaw106]

The problem I'm having is that I'm using a swing arm from a gs1000, which is wider and a rear wheel from a cb 750. Im using a laser to center the wheel so that is no problem. I have a lathe so I can machine spacers. What I'm trying to do is line up my sprockets.... The cb750 wheel has a Cush drive so I'm planning on machining that down to get my sprocket where I want it. I just don't know how to go about it??? I figure if I can get a rough measurement from center line to inside face of sprocket and transfer that to my new wheel then everything should line up in theory...

 

[hmusket]

Maybe you can center your rear wheel and put the flat of a yard stick on the face of the front sprocket, and extend it back to the rear sprocket to measure any difference.