1981 gs750 (gs750e) Retro Racer project

[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

 

[Guest]

Thanks for all the info
I have couple of questions though.. It was quite hard to get the measurements right.

I just measured my top clamp, and I used a straight piece of rod and did a lot of adding/subtracting. With the clamp installed and the fork tubes raised above it, I laid a piece of drill rod across the tubes and used calipers to measure from it to the start of the middle hole. Knowing the diameter of the fork tube, the drill rod, and the steering stem hole, you can determine the offset.

Heck, if that mill you used has a DRO, couldn't you just use that? That thing is sweet.

Excited to see where this build goes!

 

[LarsKroghStea]

I just measured my top clamp, and I used a straight piece of rod and did a lot of adding/subtracting. With the clamp installed and the fork tubes raised above it, I laid a piece of drill rod across the tubes and used calipers to measure from it to the start of the middle hole. Knowing the diameter of the fork tube, the drill rod, and the steering stem hole, you can determine the offset.

Heck, if that mill you used has a DRO, couldn't you just use that? That thing is sweet.

Excited to see where this build goes!

Will do it as you decribe the manual way. The drill is mainly used for making signs and do not have DRO.

-Lars

 

[Guest]

I should have my top clamp from Bullit Custom Cycles in a few days, so I'll let you know if my measurement method was at all accurate

 

[LarsKroghStea]

Took some tries to get the buck the way I wanted, but this is the final iteration:


20160529_194812_zpsc9rkobar by Lars Krogh-Stea, on Flickr


Hard to bend the metalplates by hand, but I'm not going for the perfect look anyway. The result is okay by my standard.


Bendingtool no 1:
20160525_174046_zpsq6sclfem by Lars Krogh-Stea, on Flickr


Bendingtool no 2:
20160525_174040_zpssrtje3v8 by Lars Krogh-Stea, on Flickr


Bendingtool no 3:
20160525_171654_zpsnjxyx8cd by Lars Krogh-Stea, on Flickr


Result ready for final adjustement. Taped a stencil on the top along the middle to so that I could flip it back and forth and get both sides equal:
20160529_155158_zpslwvsr8q0 by Lars Krogh-Stea, on Flickr

 

[LarsKroghStea]

Original rear wheel with new powdercoated rim by the side.

Snapchat-8854658473716042179_zpsjeazhfri by Lars Krogh-Stea, on Flickr

 

[Rensdw]

Man, how you are making that seat just gave me the confidence to go and make my own like that, thanks a lot!

 

[LarsKroghStea]

Man, how you are making that seat just gave me the confidence to go and make my own like that, thanks a lot!

Thanks Looking forward to the result. Will post a picure of mine when the welding is done.

 

[LarsKroghStea]

First try with the powdercoating equipment. Next up will be the spokes and nipples.


Snapchat-8548424895810138590_zpshz6x3crk by Lars Krogh-Stea, on Flickr


Snapchat-5750727464801896914_zps9h60mojs by Lars Krogh-Stea, on Flickr


Snapchat-3550012378084688016_zpshtswbcoz by Lars Krogh-Stea, on Flickr


Snapchat-207582542816693880_zpszzjh0kdu by Lars Krogh-Stea, on Flickr

 

[LarsKroghStea]

Had the time to powdercoat the spokes and nipples today. Covered half of the threads on the old spokes with masking tape and screwed the new nipples on them so the nipples would get completely covered in powder. Coated the new spokes by them selves. The finish was as smooth as the rim I ordered with professional powdercoating. The hub I did a couple of weeks ago didn't get quite as nice, and I understand now that it was because I didn't heat it enough before the baking. This causes the powder to not float properly.

Anyway, here are the pictures:

20160707_133821_zpsx0ns4jgx by Lars Krogh-Stea, on Flickr


20160707_145214_zpsppwflcp1 by Lars Krogh-Stea, on Flickr


20160707_212122_zpsp8rix6ty by Lars Krogh-Stea, on Flickr

 

[steve murdoch]

The quality of the work on this site never ceases to amaze.
Nice work, Lars.