Not sure, but check out http://www.ram.mc. They have aftermarket swings arms for the full Ninja lineup. An email to them might get you info on whether or not an aftermarket swingarm is available for the ZR. My memory wants to say that one of the pics from a European bike on the ZR-7.com page showed a different swingarm on the ZR. Not sure though.
Know what gets me ? you go searching for suspention parts, @ Works performance, or @ hyperpro, and all the Ninja's are listed, but not the ZR-7. I know they sell an S load of Ninja's, but can't they come up with a cross refrence for our ZR ? Sometimes you'll catch one, but rarely.
I think a rear upgrade would work wonders, but those I've seen cost over 4 bills !!
I think the stock swingarm change would be really over the top. The front end really just needs the progressive springs, a measly 75 bucks. Guess I'll be doing my front end long before my rear.
Almost any set of forks will work as long as the steering stem from the ZR-7 is used. The donor forks will need to have the original steering stem cut/pressed out and then some welding or reaming to get the ZR-7 stem into the donor triple clamps may be in order. The biggest problem here is that the rake of the ZR-7 is higher than most of the sportbikes, thus the forks tubes on the ZR-7 are about an inch longer than the ZX-6/7/9 forks. You would lose precious ground clearance as a result. If you were to use these forks, you could have a custom top triple clamp made that would make up part of the difference. A better solution might be to find other slightly older sport models that have longer fork tubes, I really don't know which ones but I'd probably look at the mid-90's CBR900RR first.
Changing the swingarm is kind of a trial-and-error thing. You'll want to find something aluminum, beefy, that has a length, pivot axle diameter and pivot width very close to that of the ZR-7. You might try collecting a database by going to bike boneyards or pestering people on Ebay to measure their part-out bike swingarms. Luckily, 95% of junked bikes are smashed in the front and the rear is fine. I'd probably start looking at ZX-6R's first. Note that the shock mounting and suspension linkage will likely be different, necessitating changing to the donor bike's rear shock and possibly re-welding the top shock mount to match. There will probably also be some machining necessary to get the new swingarm pivot axle to fit into the ZR-7 frame and possibly some juggling with the pivot bearings.
In any case, it might end up being easier to use the handlebars, brake parts, wheels & wheel spacers from the donor bike on the modded ZR-7 rather than trying to use the original parts. No matter what you're talking big $$$. The final possible caveat will be the alignment of the rear wheel to the front, which could put the rear sproket out of alignment with the front sprocket. This could force you to do silly things like switch to a 520 chain and use spacers under either the front or rear sprockets, or even use custom-made engine mounts to move the engine a few mm in one direction or the other. Unless you are a qualified machinist with the right tools at your disposal, the work will be extremely expensive. In the end, unless you want to race the ZR-7, are wealthy with money to burn and/or are completely insane, selling it and buying a xxx-R bike is going to be much more cost-effective.
At 1455mm/57.25inch the ZR-7 wheelbase is in fact closer to the XR650 Honda trailee (1480mm/58.25), or about 2-3inches longer than say a TL1000S (55.7inch). Even allowing for increased trail I think a sports bike swingarm would be way to short for the ZR-7.
A company like JMC can build a swingarm for anything if you are keen though.
hmmm...$3K for a mag swing arm. Another $4K for mag wheels. Change the front end, say another grand. Big bore kit with GPz racing cams. Misc. other odds and ends plus the base price for the bike say $16K. While it would be a hot ZR-7 I think it's butt would still be getting kicked by that $10K R1.