1981 gs750 (gs750e) Retro Racer project

[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_zps zvctmdvf 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...e-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.

[Chuck78]

Best to double check individual tire manufacturers reccomendations per tire model for fitment.

I run a 140 & 150 on DID & Sun 3.50 rims. 140 has every bit as much contact patch and weighs less, as installed on a 3.50. 150/70 fits good, 140 fits best.

[LarsKroghStea]

Best to double check individual tire manufacturers reccomendations per tire model for fitment.

I run a 140 & 150 on DID & Sun 3.50 rims. 140 has every bit as much contact patch and weighs less, as installed on a 3.50. 150/70 fits good, 140 fits best.

Will do

[Chuck78]

You also need to take into consideration the ride height changes due to tire size changes. Overall, about 1" total combined steepening of rake over stock oem sizes is good for cornering. Going with a 110/80-18 or 100/90-18 over the stock 3.25(?)x19 will help quicken steering by dropping the front slightly. Then a 150/70-18 or 140/80-18 will raise the rear up a bit as well. Assuming you are using GS triple clamps still. I prefer a 140/70-18 and 110/80-18 and taller rear shocks than stock to get a good quick feel to the steering.

If swapping modern forks, try to stick with 41mm RSU tubes so you can run GS1100GK triples or Honda PC800 triples with the steering stops modified to work with a GS frame.

CBR600F4 forks are great in VMAX 1200 43mm (93 or 94+ models 43mm tubes) triples but may require slight milling the backsides of the calipers for more spoke to caliper clearance.

GS1000 dual disc fork legs are the easiest swap on most big gs's, Sonic Springs and Racetech Gold Valves or Ricor Intiminators and you're home free with the tire diameter and shock length changes. Much better steering, 37mm stiffer fork legs as well. I have pushed my 35mm 650 forks on a 750 to the limits as well. I noticed some flex at high speeds and aggressive cornering, but the bike handled wonderfully with fork spring and valving g upgrades, Tarozzi fork brace, piggyback shocks sprung and valved for the bike. Of course going to RF900R (shorter version of Bandit forks) cartridge forks may have me seeing what I didn't know I was missing out on, but the 35's modified did the job pretty well.

[Chuck78]

Sorry, failed to clear that up. Taller diameter rear tire and/or taller rear shocks combined with shorter front tire (18" swap) to give you a combined 5/8" to 1" change in ride pitch, adding together the extra height in the rear with the difference in lower height up front, for 1" total change, will give you GREAT quick nimble agile handling on these very stable GS's

[LarsKroghStea]

Thanks for all the info

Today I made a prototype for the top clamp:







I have couple of questions though.. It was quite hard to get the measurements right. Does anyone know the spacing between the big (35mm) holes and how much offset the small hole is from the two others? I also noticed that the center hole is drilled at an angle, anyone know what angle this is? The long hole is for fitting a Motogadget Motoscope Mini:



Here's also a video of the milling process:

[LarsKroghStea]

Today I had som extra time and sat down to make at 1:1 scale blueprint of the seat.


First I checked the proportions and measurements in Gimp:





When I had all the coordinates I drew the seat up in three planes:





Tomorrow I'll try to make the framework somehow. The plan was to cut it out in MDF-wood and glue/screw the pieces together, but I see people also weld together a wireframe first, then weld the sheet metal to the frame. I'll spend some time with Google and see what I come up with.

[LarsKroghStea]

I've started on the buck for the metalshaping of the seat, but I needed to visualize it on the computer before finishing it.

[LarsKroghStea]

A couple of images from the building process. This shows how I'm making the buck.

[rapidray]

HOLY CRAP!!! You have too much free time!!! LOL!!!
Ray.

[LarsKroghStea]

HOLY CRAP!!! You have too much free time!!! LOL!!!
Ray.

Haha Not really, just needed something to do on the computer while the wife was watching Sons of Anarchy The bikebuilding is as important as the riding and I like learning new stuff and new ways to do things