2in too small??

[Milktown]

When I got my 78gs 750 a while back It didn't have a chain cover. I neglected to get until a couple days ago. As I wet to put it on I found out the rear tire is too wide to allow a chain guard without have to cut out a large section. At first I thought I had the wrong guard but then I looked at the tire size...130/90-16?! Everywhere I've looked says it should have a narrower 18in in the rear. The front has the right tire and both rims look stock can I just throw on some different rubber or will I need a new rim?

..also any good suggestions on chain/sprocket brands?

[TheCafeKid]

Unless someone has invented a elliptical rubber stretcher, I'm gonna say someone stuck a 16" "L" model rear rim on your bike. 130 is pretty much what everyone runs on the rear with cast wheels, a 120 is probably closer to "correct" but the actual size is in between and isn't really made anymore.
Your bike SHOULD have an 18" rear rim, though a 17" from a later E model would be fine too. You can continue to run the 16" wheel but as you can see it's not supposed to be on there.
All of the cast wheels have the same pattern from 78-81. In 82 the G models changed

[Milktown]

Unless someone has invented a elliptical rubber stretcher, I'm gonna say someone stuck a 16" "L" model rear rim on your bike. 130 is pretty much what everyone runs on the rear with cast wheels, a 120 is probably closer to "correct" but the actual size is in between and isn't really made anymore.
Your bike SHOULD have an 18" rear rim, though a 17" from a later E model would be fine too. You can continue to run the 16" wheel but as you can see it's not supposed to be on there.
All of the cast wheels have the same pattern from 78-81. In 82 the G models changed

Yeh I was thinking about just slappin some new rubber on the 16 and running with that rather then finding a new the original size...which brings me to why I mentioned sprockets in my first post. Im in desperate need of new ones, old ones starting to look like saw blades. Thinkink about possibly changing the number of teeth to make up for the 2 less inches in the rear tire. Any suggestions?

[TheCafeKid]

Well. In reality, the wheel size isn't quite two inches smaller. Iirc the 18 or 17 run a 130/80 maybe? So you make some size up in sidewall height.

Anyway, I would suggest swapping to a 530 chain and sprocket set up. 630s are hard to come by if you drop a chain or need a new masterlink in the middle of BFE. But alot of bikes run 530 now so they are available everywhere.
It's also less rotating mass on the wheel and motor, makes for a slight HP increase (less drive line loss). Www.z1enterprises.com can hook you up with sprockets chain spacer (you may need one behind the counter sprocket) and masterlinks. If you call them they can also recommend a good gearing ratio. I'd suggest 17F 50R but that's just me. Closest to stock ratio, and the stock ratio is pretty darn good for acceleration and decent highway rpm.