My GS500x1.5(divided by .5 cylinders)/older thing...

[makenzie71]

In case the title was confusing, I don't have a GS "twin"...I have a GS "quad"

(1981 GS750E, by the way)

To compliment my FZR600 front end...I do a YZF600 rear.  Wheel matches and it's 5X17.  I can finally run a 160 again...110/160 being my favorite combination, and something I think is perfect for the bike's wheelbase and power.

Anyway, I'm running Yamaha FZR600 forks, triples, brakes, wheel, etc up front...as I've discussed before, it's almost a straight bolt-on, with the only major thing needed is a 5mm shim under the lower bearing.

I have been running a 3.5X17 GS500 wheel in the back, but the 130 just isn't offering the traction and stability I want in a machine...it might be more because the tire is about as bald as can be, but I can't even change lanes without the bike getting fishy when it rolls across the lane divider paint.  But, I digress...

The FZR has an 3.5X18 rear wheel.  If you swap out the bearings for 20mm pieces instead of the 17mm ID it comes with you can run it in the 750, but you need the YZF600R caliper hanger, caliper, and axle spacers to make it work properly.  You're still limited to, at most, a 150mm tire...and 18" wheels are getting scarce, which means that the good tires cost more.

I opted to do a YZF600R rear wheel instead.  The bare minimum you need here are the wheel, YZF axle spacers, YZF caliper hanger, sprocket carrier, and cush.  Clearance is TIGHT, though, and you WILL have to shave a lot of the caliper hanger off to get everything to fit.  It's too tight for this swingarm, really.

So I widened mine by 1.25".  It's a little wider than the stock YZF600R swingarm, but if I ever get to do the engine swap I want to do I'll end up needing a 6" rear wheel and more room.

What I did was cut the stock swingarm twice...first to separate the spars from the pivot, and second to split the spars.  The first cut needs to be done by a professional.  I have access to proper machines and measuring gadgets to get it done...but to keep the project simple YOU HAVE TO HAVE THAT FIRST CUT 100% TRUE!  If your cut is even a few degrees off from parallel to the pivot, everything will get more complicated.

The second cut you can do with your eyes closed in the dark with a machete.

Have your machinist mark your center and mark where your limbs will be relocated to for the welder.  In my case, everything got moved .75" off center.  From here I tacked everything back together, then placed a few cuts along the parts of the spars that protruded so that it could be bent back in easily.  With luck your gaps should be fairly small...unless you went WIDE...and you won't have much to reinforce.  If you go any wider than I did you'll need to do a lot of reinforcing.

After I got it all tacked up I built a brace...very simple "U" with some flipped ends connected to the pivot by two legs.  As some of you will undoubtedly be able to tell, that is EMT tubing I made the brace from.  I feel that it's strong enough...however, this is my first jaunt at doing this and it took me six attempts to get the horseshoe right.  Now I have a good jig and established measurements...I will be making another soon using iconel tubing.  I may actually try my hand at doing the FULL swingarm.

Anyway...









Ignore the mess in the background.

My caliper hanger may bolt to the subframe, I think...it was an idea I had after I had it all together, but I really didn't design the subframe with it in mind and am unsure if it's up to the task.

Upper shock mounts will have to be extended by half an inch and the rear brake master will have to be relocated.

That's all I can think to say right now.  I go to have that gap in the middle and the joints properly welded this weekend.  Hopefully I'll have a carrier in this coming week and can install it next weekend.

[crazyfish]

Looks sweet but you might want to fill in the gap you left in the middle of the arc before too much road gunk and water gets in there and the rust gremlins get to work.... 

[makenzie71]

That's all I can think to say right now.  I go to have that gap in the middle and the joints properly welded this weekend.  Hopefully I'll have a carrier in this coming week and can install it next weekend.

[makenzie71]

Yay and I just scored the axle!  I can probably get this setup and going by late next week.

[makenzie71]

A while back I ditched the stock wheel and slapped in a 1992 Suzuki GS500E rear wheel.









I didn't so much like the tire width, though...not enough meat on the ground.  Plus, I just wanted a wider rear wheel...and I wanted something that matched the front wheel.

So I built this:









Widened 1.5" (give or take a few mm...).  Trued it up and welded the thing solid...and yeah, I had that gap in the middle filled (my guy did a fantastic job...looks like it was always this way).

I had a YZF600R rear wheel so I based most of my build off of that.

I had a HUGE problem with sprockets...the YZF600R came with 47-tooth sprockets...plus or minus a few...and that just doesn't fly with the GS750.  I ended up having to go to the Wera forum and someone happened to notice that WR250F sprockets had similar dimensions....SCORE!  I had to take a WR250F sprocket and drill the bolt holes out to 10.5mm and it slipped right on!



A gentleman on yzf600r.com (nu600rider) hooked me up with a great deal on the carrier above as well as an axle, caliper, caliper carrier, all the spacers, cush, brembo master, brake line...even the brake pedal.  In the end I was able to put this all together:



I should have got a good before pic because I put it all together backwards the first time.

Slipped that bad boy in there...



...then I had to pull it all back apart because I forgot to put the caps on the end of the swingarm pivot...then again because I forgot to put the bearings in there...argg.

In the end this is what I ended up with:





















My chain is about 2mm off...I'm having a spacer cut for it today...just have to keep my ride time tame until then.

I did have to put some shims behind the upper strut bolts, but they're long enough to be more than accommodating with my shocks.  I also had to bend the push rod on my master cylinder a bit to get it to clear my swingarm, also had to shim my muffler out about 1/4".  Only real frustrating thing was a brace for the brake caliper.  I ended up drilling and pressing a stud through the swingarm main spar and I tweaked a dogbone from an FZR600 to fit...haven't tried it out.  I'm going to go beat on the rear brake here in a bit and see how it holds/stops...I'm probably going to have to do something different, but I guess we'll see.

[makenzie71]

Next...a seat...and doing something about my battery...

[JAY W]

Kawa Z900 seat & tail would suit,set of renthals,twin lights?