1981 gs750 (gs750e) Retro Racer project

[LarsKroghStea]

I've started a project, and as I have a lot of questions, I've decided to start my own thread. The bike has now been taken apart, and has only the whels and engine on. Will post pictures as I mount new parts back on.

First task is: gather the parts to convert to spoke wheels. The bike now has the original cast wheels. I have a set of '79 brake calipers on the way as I've read in another post that I need those to get the clearing needed on the inside. I've dicided to go with original forks for now, as I want to get the bike on the road by spring, and there is alot of other things to do. I've found a front wheel on ebay that I hope will be a direct replacement ( I will fit aftermarket outer rim and keep the spokes and hub) http://www.ebay.com/itm/181902877339?item=181902877339&viewitem=&vxp=mtr . I'm also looking for a rear wheel with spokes to replace the one I have. Is that a direct replacement? I know the brake rotor in these are bigger, but can I use the brake rotor I have on now and do i need something else to do the swap? I will fit a wider (4.25") outer rim on the rear wheel.

Update: It's now been 10 years. Some of you have commented on the progress, saying the bike will never be finished or roadworthy. I don't blame you, as I've been very on and off over the years.

But.. here we are, and I didn't give up. The bike is in it's final form, and I've been riding it around town and for trips up to 2-3 hours. Some things have come up, and I will still make changes, but the bike won't be off the road again unless something brakes.

I'm now keeping an index, below, where I list some of the major changes, problems and solutions.



INDEX:

[TABLE="align: left, border: 1, cellpadding: 1, width: 800"]
[TR]
[TD]Photoshop image of how I envisioned the final build[/TD]
[TD]Post #17, page 2[/TD]
[/TR]
[TR]
[TD]Making a wooden buck and bending the metal sheets for the seat[/TD]
[TD]Post #34, page 3[/TD]
[/TR]
[TR]
[TD]Laced and powdercoated rear wheel with 150/70-18 tyre[/TD]
[TD]Post #40, page 4[/TD]
[/TR]
[TR]
[TD]Welded seat[/TD]
[TD]Post #51, page 4[/TD]
[/TR]
[TR]
[TD]Seat padding and diamond-pattern cover[/TD]
[TD]Post #61, page 5[/TD]
[/TR]
[TR]
[TD]Making custom rearsets[/TD]
[TD]Post #84, page 6[/TD]
[/TR]
[TR]
[TD]520 conversion. Rear sprocket is for a Suzuki DR 750, front sprocket is for various 90's Kawasakis.[/TD]
[TD]Post #93, page 7[/TD]
[/TR]
[TR]
[TD]Making shortened exhaust[/TD]
[TD]Post #113, page 8[/TD]
[/TR]
[TR]
[TD]Custom wiring diagram for Motogadget mo.unit blue and Motoscope mini[/TD]
[TD]Post #120, page 8[/TD]
[/TR]
[TR]
[TD]First test ride[/TD]
[TD]Post #149, page 10[/TD]
[/TR]
[TR]
[TD]New choke lever[/TD]
[TD]Post #159, page 11[/TD]
[/TR]
[TR]
[TD]Left side cover[/TD]
[TD]Post #203, page 14[/TD]
[/TR]
[TR]
[TD]Designing and printing Left hand controls[/TD]
[TD]Post #283, page 19[/TD]
[/TR]
[TR]
[TD]Right hand controls with push-buttons[/TD]
[TD]Post #290, page 20[/TD]
[/TR]
[TR]
[TD]GSXR 750 front conversion[/TD]
[TD]Post #296, page 20[/TD]
[/TR]
[TR]
[TD]Hooking up Domino throttle and cable[/TD]
[TD]Post #341, page 23[/TD]
[/TR]
[TR]
[TD]Modefied left footpeg-mounting plate[/TD]
[TD]Post #389, page 26[/TD]
[/TR]
[TR]
[TD]Rear lights[/TD]
[TD]Post #390, page 26[/TD]
[/TR]
[TR]
[TD]Warning lights with LEDs, resistors and soldering board[/TD]
[TD]Post #391, page 27[/TD]
[/TR]
[TR]
[TD]Yamaha R1 caliper conversion - with milling job[/TD]
[TD]Post #396, page 27[/TD]
[/TR]
[TR]
[TD]Making front fender brackets and mounting fender[/TD]
[TD]Post #421, page 29[/TD]
[/TR]
[TR]
[TD]Making bracket for side mounted license plate[/TD]
[TD]Post #422, page 29[/TD]
[/TR]
[TR]
[TD]First real ride with GSX-r750 forks, R1 brakes and Cognito Moto 19" front wheel[/TD]
[TD]Post #423, page 29[/TD]
[/TR]
[/TABLE]

 

[Chuck78]

Rear disc wheels are harder to find in spokes, but if you shop around here with a WTB ad you can likely find a set of alloy rim GS1000 wire spoke wheels. I got 3 different members messaging with GS1000 alloy rim spoked wheels in various conditions, after a few weeks of looking for wire spoke wheel hubs with a GS Parts section Wanted ad.

Also just look for a set of GS850/1000 straight leg forks for the easiest swap, as they are 37 mm diameter and much stiffer, and you can get cartridge emulators and springs from racetech that will make the dampening substantially better and make it a more performance-oriented ride. Then you can get the aluminum lower and upper triple off of a straight leg fork GS1100E, you'll have to look at the model year pictures to determine which year had the straight leg forks and which years have the leading axle. The triples look different, the leading axle ones that you do not want, they have a lower triple that looks more like a big rectangle, the ones we want are aluminum lower and have more offset and kick forward more at angles.

you can also do the popular twin pot brake mod, search for salty_monk's thread on that "twinpot mid for 78 skunk." This will be by far the best bang for your buck in terms of a substantial fork/brake upgrade. Running 94 through 97 VFR 750 non-abs forks is the best thing you can do in a cartridge fork swap (41mm legs) if you want to retain wire spokes without much hassle with clearance to the spokes from the brake calipers.

 

[Chuck78]

Most of the modern cartridge forks will require lots of researching wheel diameters and corresponding speedo drives in the axle size you need for the modern fork (&swapping to larger i.d. bearings and custom machined spacers. Or the easy route, bush down the fork with a spacer to the GS axle size with help from a machinist. The 37mm GS forks and an all balls needle bearing conversion is the easiest by far. Cartridge emulators, springs, & a Tarozzi fork brace make it a great handling vintage setup that is almost a bolt on.

 

[LarsKroghStea]

Rear disc wheels are harder to find in spokes, but if you shop around here with a WTB ad you can likely find a set of alloy rim GS1000 wire spoke wheels. I got 3 different members messaging with GS1000 alloy rim spoked wheels in various conditions, after a few weeks of looking for wire spoke wheel hubs with a GS Parts section Wanted ad.

Also just look for a set of GS850/1000 straight leg forks for the easiest swap, as they are 37 mm diameter and much stiffer, and you can get cartridge emulators and springs from racetech that will make the dampening substantially better and make it a more performance-oriented ride. Then you can get the aluminum lower and upper triple off of a straight leg fork GS1100E, you'll have to look at the model year pictures to determine which year had the straight leg forks and which years have the leading axle. The triples look different, the leading axle ones that you do not want, they have a lower triple that looks more like a big rectangle, the ones we want are aluminum lower and have more offset and kick forward more at angles.

you can also do the popular twin pot brake mod, search for salty_monk's thread on that "twinpot mid for 78 skunk." This will be by far the best bang for your buck in terms of a substantial fork/brake upgrade. Running 94 through 97 VFR 750 non-abs forks is the best thing you can do in a cartridge fork swap (41mm legs) if you want to retain wire spokes without much hassle with clearance to the spokes from the brake calipers.

Thanks for all the good info. Read through your build thread and you're doing great stuff with your bike! I'm not going to do a full fork switch right now. I just want the easyest route to wire spokes front and back plus a wider rear wheel. Do you know if the ebay-wheel I linked to will fit? You mentiion the gs1000 rear wheel, but isn't the gs750 rear wheel an option if I'm not using the outer rim anyway? http://www.motorcyclespecs.co.za/model/suzu/suzuki_gs750 76.htm (link to gs750 with wirespkes and disc brake) Or is it those wheels that are hard to find..? Also the speedo issue isn't really an issue, because I'm gonna buy a motogadget mini digital speedo with wheel sensor.

 

[Chuck78]

Yes 750& 1000 rear hubs are the same. Not sure if you could ever get the wire spoke wheel 550 with a rear disc, but they did make mag wheel 550's with rear disc.

 

[Chuck78]

Only the 77, the rear disc was larger @ 295mm, same as single disc fronts. The 78+ were 275mm rears, same rotor as the dual disc fronts (front right dual disc rotor if it has a drilled venting pattern in the friction surface)

 

[John Kat]

It's perfectly possible to fit a GS 750/1000 laced wheel in a modern fork.
Here's how I did it.
http://www.thegsresources.com/_foru...rk-upgrade-for-17-18-and-19-quot-wheels/page3

 

[Chuck78]

I figured as much, and have seen others doing that, but that requires custom machine work, and that is why I said that it's not terribly easy. it would be for me as I have machinist friends, but not everyone has that connection.good read on the link you posted. I prefer the Honda forks because the rotors and brakes are much more adaptable to GS hubs/wheels without much custom machine work. good to know that there are more options for proper height of forks however. Thank you for the knowledge.

 

[LarsKroghStea]

It's perfectly possible to fit a GS 750/1000 laced wheel in a modern fork.
Here's how I did it.
http://www.thegsresources.com/_foru...rk-upgrade-for-17-18-and-19-quot-wheels/page3

Thanks for the link I have access to a lathe and a manual mill in my fathers garage and a cnc router that handles aluminum at a friends. I have some mecanic experience with old VW Beetles, but this i my first venture into modifying motorcycles. Winters here in Norway are long, so there's plenty of time to trial and error before spring. I'm also grateful to see that there's so many of you that is willing to give of your time and knowldge. It's just like the beetle community

 

[Chuck78]

I can't wait until I finish rehabbing my old house and get it sold the spring, I definitely plan on buying at least a Harbor Freight milling machine and a used lathe...and a decent small or medium bandsaw. that will enable me to do all of these fork conversions and other various axle adapters, custom rearset work, custom rear brake hangers & rotor adapters, etc...

Glad to offer advice, hit me up any time! What running condition is that 750 in? Most are in dire need of a good carb cleaning, all new carb o-rings, top& bottom gaskets, & sometimes a new matched needle & seat set.

Great sticky tires for excellent cornering? Pirelli Sport Demons are #1, Shinko 230 TourMaster & Shinko SR741 (for larger 130/70 & 140/70 rears) are the best for the money, Bridgestone Battleax BT45's are same grip but more sizes available than Shinko but more money, tread pattern looks more fitting on a vintage bike. Then There's the old standby Avon AM26 RoadRider if you are doing long distance trips or riding lots of flat straight roads where you need a longer tread life but still want good cornering.

Last thing I should drop on you is that you need to ditch the stock regulator-rectifier IMMEDIATELY, they fry stators eventually. Replace it with the Compufire 3 phase series regulator rectifier or a used unit from a Polaris RZR 800 (or Can am or SeaDoo), the Polaris OEM # you need to search eBay for is 4012941. It is made by Shindengen, model SH775, but the Polaris OEM # is what you will find it under.
Go through the entire wiring harness and use DeOxit contact cleaner on all connectors, replace all brittle or bad connections/connectors, lube all with silo cone dielectric grease, crimp any loose bullet or spade connectors for a tighter fit, check and clean/dielectric grease all grounds.... clean the insides of the kill switch, ignition switch, headlight switch. If yours has a head light that switches on & off, there is one leg of the stator output run through the lighting switch to disable it if lights are off. Abandon this when swapping to the SH775, as it is a series circuitry r-r, it us more advanced and regulates the voltage by rapid cycling the stator wires open & closed, vs most others of the standard shunt style, which regulate by rapid cycling short circuiting all the excess voltage straight to ground, which makes the stator run very hit at full load continuously. The series style gives the stator a break until that extra full output is needed. Much better.

Good luck!

 

[LarsKroghStea]

Glad to offer advice, hit me up any time! What running condition is that 750 in? Most are in dire need of a good carb cleaning, all new carb o-rings, top& bottom gaskets, & sometimes a new matched needle & seat set.

Good luck!

Thanks! The bike is running pretty well. Previous owner has changed a lot of bearings and seals. He also put on a new set of (used) carbs, but as I'm going to paint them and have the shiny pieces galvanized (I think is the right word) in silver finish, I'll tear them apart and check everything. If someone has a link to a good thread about carb service it would be great As I'm running a Kercher 4-1 and will replace airfilter with a single K&N filter (not pods, I'm keeping the plenum) I'm also thinkin of getting a stage 3 kit. I did that for my old Kawasaki ZX7R and it worked great.

 

[LarsKroghStea]

Well, I have a new question. Seems like someone damaged the threads to one of the exhaust bolts. What's the best way to fix this?

 

[Chuck78]

Threads in the head? Helicoil repair kit. Get the longest one you can find in that size, probably from ebay. For $15-25 you can get a basic kit from an auto parts store but you may have to use two inserts stacked on each other. You drill the hole larger, run a special tap in that is one size or so bigger but same thread pitch, and then thread the coiled stainless inserts in.

There is also the TimeSert insert type that is basically a full sleeve with threads on the inside and outside, requires the holeto be drilled much more oversized.

Always use good antisieze lube on exhaust bolts, and use caution when removing them when they've been in there firever. Hot engine, lots of penetrating oil days and weeks before, spray bottle CO2 or touch an ice cube to the bolt head after engine has been warmed up. Then remove. So.Rome likely broke a bolt off in the past and drilled it out crooked, messing up the threads.

A 550 head I have here just simply has 2 or 3 of the holes tapped one diameter larger and oversized bolts installed on those. Use stainless fasteners and split spring type stainless steel lockwashers on reinstall, and antisieze the threads.

 

[LarsKroghStea]

I've found the hubs now and I have another question. I've read somewhere that some spoke wheels are Japanese indexed and some are European indexed. What are the differences and does anyone know how the Suzuki wheels are indexed?

 

[Chuck78]

What is the difference? Indexed? The way the spoke holes are drilled???? I've never heard of this.

I did run into a Campagnolo bicycle hub once that had the holes drilled in line with each other on both hub flanges, which makes lacing them very difficult as it requires every other spoke to be shorter/longer. They should be offset 1/2 hole from one flange to the next. Is this what you are referencing?

 

[LarsKroghStea]

What is the difference? Indexed? The way the spoke holes are drilled???? I've never heard of this.

I did run into a Campagnolo bicycle hub once that had the holes drilled in line with each other on both hub flanges, which makes lacing them very difficult as it requires every other spoke to be shorter/longer. They should be offset 1/2 hole from one flange to the next. Is this what you are referencing?

I don't actually know. Guess I'll send an E-mail to Excel rims about it.

 

[LarsKroghStea]

The Noise_bike_mad_skills_zpsvjqtjnqk by Lars Krogh-Stea, on Flickr

This, I believe, is the final color scheme. I'm aware that I've used a CB750 as base here, but I'm getting tired of Photoshop and wanted a quick mockup. I'm gonna use another bigger headlight and black exhaustwrapping together with a shorty style muffler i think. I'm also going to keep the intake plenum.

 

[LarsKroghStea]

After a lot of research this is what I've concluded with: I've bought laced wheels from a 1979 gs750. The front wheel is good and I will use it as it is. I've moved the brakes over from the original wheel.

20160218_132839_zpsgwncswkx_edit_1455805074944_zpszvctmdvf by Lars Krogh-Stea, on Flickr


The rear wheel:

20160218_150912_zpslqcfb0av by Lars Krogh-Stea, on Flickr

Here I'm going to keep the spoke hub which fits perfect with the original disc brakes and sprocket carrier. I want a 150/17-18 rear tyre on it so I'll order a 4.25x18 aluminum rim and 6mm shorter spokes from Central wheels in the UK. When that's fitted I will have to research what to do to keep the chain from hitting the tyre sidewall.

 

[steve murdoch]

You can use a 3.5" rim with a 150 tire.
http://www.thegsresources.com/_forum/showthread.php?152914-Can-I-run-a-150-tire-on-a-3-5-rim

 

[LarsKroghStea]

You can use a 3.5" rim with a 150 tire.
http://www.thegsresources.com/_forum/showthread.php?152914-Can-I-run-a-150-tire-on-a-3-5-rim

Yes, I probably could. But I dont think it would be the best solution..
The current rim is 2.15", so I'll have to change it anyway.