'83 GPz750 Resto-Mod (pic heavy)


Been Around the Block
Hey all,

I been lurking for a while but I'm more into building streetfighters but thought I may post my newest project here.

I've been working in the garage off and on for about 3 weeks now. I'll cram all the pics in the first thread to bring everyone up to speed.

It's a '83 Gpz750 that I picked up cheap from a kid who needed money for a car. The bike didn't run, had a title issue, and was sitting outside in the rain when I picked it up.


When I picked up the bike I did a quick once over for what it needed. First thing was a front tire as it was dry-rotted and leaking, The next obvious items that needed replaced was the sprocket and chain. The rear sprocket was missing almost half of its teeth. :blink:

So I did what any normal person would do, I started browsing Craig's List and found this for a price I couldn't pass up.

After a few hours in the garage, I removed the stock swingarm and linkage. A little grinding and massaging to the VFR arm, I ended up with this.




Next up I made a jig to properly locate the suspension pick-up points from the VFR frame.

Then I started de-tabbing the frame of its original shock mounts and center stand brackets.





I made swingarm spacers and spent most of the time double, triple, and quadruple checking the fitment. I was able to get the chain lined up and get the swingarm snug between the frame rails. I just hope when I cinch down the pivot bolt it doesn't bind everything up.

I found a new, unused 5/8" offset sprocket which lined up the chain perfectly.

It seems counterproductive to then make and add back tabs to the lower crossmember, but the original lower suspension and center-stand mounts were in the wrong locations.



Then I tack welded the lower tabs on using my handy dandy jig I made.




I moved on to making an adjustable linkage setup. As far as I know, this has never been done before so I bought a set of used lowering links from a Hayabusa as they were about the shortest I could find and went from there.








I made a couple bungs for the upper shock bolt. Tubes will then be welded to the bungs and then to the original shock cross-member and another spot to be determined.





Some chromoly tubing and some notching and here is where I'm at so far.



And a nice parting shot...

Thanks for looking.

Later, Doug
Nice progress mr!
Tou had a title for that bike in your hand when you started i assume,so you dont do to much labour without getting it back?
i`m in anyways :)
Yeah. The title had a glitch but I got it cleared up and it's in my name. I made sure of that before spending a penny on it.

Later, Doug
Nice work. 8)

I almost shit myself when I saw the pic of that rear sprocket!!!!! I think you can get a few more seasons out of that thing!!! :eek:

Those GPZs can be cool when fightered properly. I have seen a few badass examples. I think the body work and the front end take some vision to pull off a good look. They are definately dorky looking in the stock configuration. I look forward to seeing what you do.
Sweeeeeet :D The single sided swinger looks wicked! The custom spacers and all...well, I just cant help but be jealous, wish I had that kind of fab ability.

What's your plan for the shock mount? Have a nice triangulated design in mind?
RedBullEnema said:
What's your plan for the shock mount? Have a nice triangulated design in mind?

I will have a lower right tube and then an upper left and right tube. I plan on having one more smaller tube between the upper two near the shock just to keep everything square and from shifting left to right.

Progress has been kinda slow since my garage is unheated and with the holiday coming up too. I plan to be back on the project next week. I got some parts in last week and I'm wanting to see how the play with the bike.

Later, Doug
Sounds good! I hear ya on the unheated garage, it's the main reason I havent touched my bike in weeks now. Instead of spending holiday cash on the bike, Im opting to spend it on garage door insulation and a heater ::)
skyler said:
Great work. I wish I had 1/100th the talent!

Thanks. I've only had a 10-week course in the basic use of a manual lathe and vertical mill, otherwise my skills are self-taught through trial and error. Trust me when I say not every little task or project goes according to plan. The key is to learn and adapt from your mistakes and overcome the challenges.

Later, Doug
I really haven't felt like dealing with notching the rest of the tubes at compound angles so I've been gathering and fitting parts over the last few weeks.

I got a '98 Vfr800 front rim, a set of Zrx1100 forks and a set of Zx11 triples with handlebars to start.

First thing was to buy some 25mm ID bearings for the Vfr rim to go from the 20mm stock axle to the 25mm Zx11 axle. But then I realized that the 20mm ID inner tube bearing spacer would be impossible to use so I took a chance and ordered a used Zx7 spacer hoping that it would be too long and I could trim it to size. It was so that was easy enough to shorten in the lathe.

Then I found out the Vfr inner hub has some extra casting material that needed to be filed down to let the bigger OD of the spacer tube pass through.


So with the correct bearings, everything played well together until I had to figure out the wheel spacers. Because the Zx/Zrx11 uses a mechanical speedo drive the left axle clamp is offset to get the needed room. This meant that I could not simply make two identical spacers. But here's what I came up with...the left spacer being about 4mm longer than the right.




Everything together and ready for me to figure out brake fitment and spacing

Which lead me to my next headache: finding a set of 310mm rotors that have the correct offset and bolt pattern for a Vfr800 rim in a set of Zrx1100 forks held in place by Zx11 triple clamps. I've looked and they don't exist. So I did a lot of research and found that I could possible use a set of Cbr600RR rotors or certain models of Gsxr rotors with the right adapter/spacer. I found a set of used aftermarket Cbr600RR rotors for a good price and bought them just so I'd have a starting point.

I also bought some 5" OD x 1.00" thick 6061 round bar stock from eBay.

All was right with the world as I had drawn up some sketches of the spacer/adapter until I placed the rotor on the wheel to see what actual offset I needed.

It turns out that I failed to take into account a small lip to hold the rotor concentric to the space. So now I'm pretty sure that the fastener that will hold the spacer to the rim will also try to take up the same space as the concentric lip. And that's where it's been sitting for the last week or so.

Any thoughts besides buying more aluminum and different rotors?

Later, Doug
Floegstad said:
Do tou have a pic ofyour gsxr?

It's in the "if I crash it, so what" stage. I'm thinking of selling it but if I decide to keep it, I'd like to do some sort of smaller tail section.



Later, Doug
I have some nsr/rgv 250 singleseat units and a xr 750 mold to make tracker asses somewhere,but i think the shipping costs more than what theparts are worth.
Thanks Floegstad. If you were in the States, I'd take you up on a RGV seat unit.

I forged ahead today on the brake rotor adapters/spacers. Let me just say that working with 5" OD stock on a 7" swing lathe takes some out of the box thinking but I think I got most of the problems solved except the spacer-to-rim mounting bolts being so close to the lip. Using socket headed bolts and thinning the lip a small amount will hopefully completely solve the issue.

First I drilled a hole in the center and used an expanding arbor to hold the workpiece so I could form the lip that keeps the rotor concentric. Once that was done I drilled and tapped two holes and used those to mount the piece to a faceplate where I could bore the ID to fit over the rim's hub.



Then with some careful positioning I used a transfer punch to mark two of the holes for the spacer-to-rim bolts.


I still need to finalize the thickness, drill the other 8 holes, plus clean it up a little to reduce some weight, but here it is in a temporary state.

At least I made progress, as I've been brainstorming about this for a week or so now.

Later, Doug
I finalized one side today. I was able thin the lip and get enough clearance to use socket headed screws just fine. The spacer/adapter actually ended up thinner than I thought but still plenty of material for strength.




How it looks all bolted up.

Just about as centered as I think I can get it.

Later, Doug
Since the holiday is done and life is back to normal, I made my way back to the garage and made the third version of the right lower shock mount tube.


But I'm not sure if I want to keep a similar design for the upper tubes or go parallel with them..


Later, Doug
Soooo........the Vfr800 rim I bought turns out to be a 16" Cbr900RR front rim. I didn't notice it until I went to mount the 17" mock-up tire I have and the tire practically fell over the 16" rim. So now I'm back to looking for a 17" Vfr rim plus trying to resell the 900RR rim since it's been more than 2 weeks and the seller won't take a return.

I'm hoping that when I do get a proper 17" rim my axle spacers and brake adapters will still work but I doubt it.

Later, Doug
I'm in a holding pattern for a front rim, so I forced myself to finish up the rest of the tubing for the shock mount. I cut a small thin sheet metal brace off the frame and replaced it with a cross-tube a bit lower. I assume the stock piece was to keep the frame loops from spreading which mine will also do. Then I tackled the top right tube and then finally the top left tube. I'm going to have to find a professional welder to finish welding everything together as I've read chromoly needs to be TIG'd to mild steel to reduce stress and cracks.

From the back

From the top

From the side

Also the seat/tank hold down bracket bolts had been replaced with 6mm bolts that look like they were welded on by a 6 year old kid with a stick welder. I cut off the yucky stuff and drilled 8mm holes in the correct location. I then machined down the head some short 8mm flange bolts and welded them on. I think they look much better and fit the 8mm holes in the bracket better than the smaller studs.




Later, Doug
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