Need help with GS550es wheel swap

[Guest]

I've had this bike for years and I'm finally getting to finishing it. I'm having a problem figuring out how to get the rear wheel centered. I'm using early 90's gs500e wheels and forks. The front end is done. I thought the rear end would be easier but I can't figure out what to measure to. The swingarm is asymmetric I guess for sprocket and chain clearance. I have a lathe and don't have a problem making new spacers but I have no idea what I need. I can't seem to find a point on the bike to measure to. If I knew the offset of the swingarm it would be easy. Any help is much appreciated, thanks

[kingofvenus]

I stretched a string on each side. From the front of the front wheel to the rear of the rear. Lazer level stuck to the side of the rear sprocket aimed forward to the countershaft sprocket.

[amartina75]

Thanks for your suggestion but with the bike being fully assembled and not having a way to plumb it and hold it straight I thought that would be difficult and prone to too much error. I think I have it sorted out. I put the factory wheel back on and took some careful measurements. With a straight edge held on the outside of the swingarm I measured; left side, 4 1/16" to edge of rim, 2" to center of sprocket. Right side 3 21/32" from edge of rim. That's a factory offset of 13/32" or .403"
with the gs500 wheel on the bike (and a 1/8" spacer between the calliper bracket and wheel spacer, because that's what it needed to center the rotor and make the overall axle width the same between the two wheels at 8 3/8") I measured;
3 9/32" on the left side to the rim and 1 13/16" to center of the sprocket. 3 5/64" on the right side to the rim. That's a difference of 13/64" or .203"
so the gs500 wheel needs to go towards the right .203" to match the factory offset. I did that by milling the brake caliper mount by .203 on the outside edge and putting a .203" spacer on the sprocket side.
Once done and reinstalled my offset matches the factory setup exactly and the sprocket is exactly 2" to the center.
Of course I am assuming that the wheel was right before, but I have no reason to think it wasn't. The bike was all original and no evidence of any damage or abuse anywhere, and I've ridden it up to 110mph or so more then once.
hope this helps someone in the future,