1981 gs750 (gs750e) Retro Racer project

[Grimly]

Excellent. I'll be fitting a replacement petcock shortly and haven't been too impressed by the size of the outlets of the ones I've seen.
That, and filters. I've always had a filter, but they've been car-sized ones, as I've got plenty of room to fit them, having the single carb. Even so, it pays to check fuel flow every so often just to make sure they're delivering what they should.

[LarsKroghStea]

Excellent. I'll be fitting a replacement petcock shortly and haven't been too impressed by the size of the outlets of the ones I've seen.
That, and filters. I've always had a filter, but they've been car-sized ones, as I've got plenty of room to fit them, having the single carb. Even so, it pays to check fuel flow every so often just to make sure they're delivering what they should.

Maybe I'll install an empty glass filter, just so I can visually inspect the flow..

[LarsKroghStea]

Did a short test run yesterday, and the bike pulls good through the gears. Didnt' get the engine fully warm I think, because there was a "scoffing" sound in the front wheel. Couldn't se anything, so it might be brakes, but I'm leaning towards bearings. I think I ordered an Allballs set a couple of years ago, but I can't remember if did the switch..

Next task anyway, is to make make fastners for the seat.

[Buffalo Bill]

Well, I learned a few things this week. Very useful info about fuel flow.
I like your side cover work too.

[LarsKroghStea]

Well, I learned a few things this week. Very useful info about fuel flow.
I like your side cover work too.

Thanks man And I really like this forum for all the helpful people and all the good ideas I've picked up.

[LarsKroghStea]

Today I'll also throw in a picture of a great deal. I have and old (2007) Shark carbon Composite helmet. It fits me perfectly and I haven't found any other helmet I'd rather use. It was quite expensive, but I got a good deal on it as I bought it, and a full Goretex outfit plus boots and gloves, together with a used Kawasaki ZX7R. Okay, I'll post a picture of that too:
1909837_22450845914_8814_n by Lars Krogh-Stea, on Flickr


At the time I thought that was the coolest bike you could have. Much cooler than the new ZX10R. It was large, pretty heavy for what it was (about 200kg) with about 120 hp. But the sound was like a racing car, and everything was making rattling or metal noises. That was when I realised that I'm never going to buy a new fuelinjected smooth riding bike. I wanted the rawness. But, I digress.. The point is, that I only had the black visor for my helmet. Someone (that's an even longer story) scratched up the clear one. The black visor is not road legal and impossible to see through at night or in tunnels. A new original visor costs about a 100$. Yesterday I found that a chainstore nearby sold some low cost helmets from a manufacturer that had copied the snap-on visor attachment that Shark uses. And they were selling out the rest of the spare visors. I bought two clear ones and two gold/mirror for about 10$. Both are awesome. The gold mirror gives good visibility, but it's impossible to see in through the visor. They look like this:
Snapchat-1984076064 by Lars Krogh-Stea, on Flickr

Next part of the project is to buy a set of car hood latches and use them to make a fastening mechanism for the rear seat:
Panserlås by Lars Krogh-Stea, on Flickr

[LarsKroghStea]

Spendt most of the day gardening and working on my home gym.. both me and my sons miss going to the gym in these Corona-times. Did get the time to buy the hood-locks though. Here are some pictures of how i envision the fastening device for the rear seat. I'm putting some rubber between the seat and the frame to prevent vibration and to put the hood-lock under tension so it won't rattle. I will also have to test which position is best.. I'll either drill and tap the square tubing or drill two metal pieces to clamp over the square tubing. We'll see.


Setefeste by Lars Krogh-Stea, on Flickr


Setefeste by Lars Krogh-Stea, on Flickr

[LarsKroghStea]

I guess it's when you start riding that the errors you've done come back to bite you.. I thought the ride was extremely harsh, and when I went out yesterday to bounce the shocks.. this happened.

I thought the hash ride was because of the thick oil and the cold weather, but I could just as well ridden with steel rods for shocks
I feared the worst..

that I had to buy new ones.


I took them apart to see what was wrong. Apparently the vibrations from running with thick cold oil rattled loose the end screw (1m) from the rod (3). Don't mind the arrows. That made the whole valve sink to the bottom and the spring pulled the rod through part 1c, wich is what it bottoms out on when I bounce the bike. 1c rests on 2a and that tube rests on the shim 2c on the bottom of the shock body. The only part with som visible damage was on 2c on one of the shocks. Some markings and it's bendt, but very little. I'm reusing it as it doesn't have much valving function.


Dempere by Lars Krogh-Stea, on Flickr


The internals, washed and end screw torqued to spec with a dab of blue locktite. Filled up the shock with new SAE 5 oil.


Dempere by Lars Krogh-Stea, on Flickr


The cool thing about having built a home gym, is that I've apparently also built a pretty safe and easy way to compress springs


Dempere by Lars Krogh-Stea, on Flickr


Dempere by Lars Krogh-Stea, on Flickr

[LarsKroghStea]

The shocks are back in working order Next up is safetywiring of the rotors and rear sprocket. Some of the safety tabs are in bad shape and one of the screws in the front disc came loose. Before i do anymore testdriving I'll have to go over the whole bike and refit the screws with with correct torque and loctite per manual. There's been too much jumping back and forth over several years and I have clearly forgot where i've test-fitted parts and where I've done them up correctly. Safety first (from now on)!

[LarsKroghStea]

Not much wrenching today, but I've been at my dad's and picked up the rest of the parts and some tools. He also handed me down an old pillar drill:
IMG_20200506_213845 by Lars Krogh-Stea, on Flickr


I'll use that to drill holes for the safetywire.
IMG_20200506_220255 by Lars Krogh-Stea, on Flickr


I also got my safetywire pliars:
IMG_20200506_220245 by Lars Krogh-Stea, on Flickr


And my smaller torquwrenches:
IMG_20200506_220303 by Lars Krogh-Stea, on Flickr

[LarsKroghStea]

While I was there, I also got some parts.
New BTR UK made brakelines:
IMG_20200506_220338 by Lars Krogh-Stea, on Flickr


New Domino throttle control with teflon cablesleeves. These are for push/pull applications, but I'll only use one wire and keep the other for spare. The controls come with three different ratio cams (stock photo, didn't want to unpack them):
domino-xm2-quick-throttle-control by Lars Krogh-Stea, on Flickr


I've also bought Ruffian roadracing grips:
IMG_20200506_220349 by Lars Krogh-Stea, on Flickr


I did bring my 2005 GSX-R 750 USD forks, complete with radial mounted calipers and disks, although I probably won't use them just yet. I've had a plan for a while, to use the Cognitomoto comversion hub, but as this is a 1000$ solution I'm researching the possibility to use offset rotors on the original GS spoked wheel that I run now. I know ducato rotors from the bikes that came with Øhlins forks are available in both 10 and 15mm offset versions. This is a thought that came to me just the other day, and I'm not shure if it's even a possibility. Here's a picture of the forks:
IMG_20200506_220458 by Lars Krogh-Stea, on Flickr

[LarsKroghStea]

https://www.ebay.com/itm/2001-2002-748R-Genuine-BREMBO-Front-Disc-Rotor-Set-15mm-Off-Set-998R-uuu/264709961036?hash=item3da1f1754c:g:47IAAOSwaTJeooN-


These cost the same as the Cognitomoto hub, but then I would have some bad ass 320mm brembo rotors that would fit the original wheel. I'll do the measurments tomorrow

[LarsKroghStea]

Another option would of course be to try to source some narrower triples. Let me know if you have som info on this.

[LarsKroghStea]

Well.. I've done som research one the fork-swap and ordered a set of new rotors (discs). I'm not going to make the swap until everything else is in order, but it doesn't hurt to start collecting parts early. I have the original GSXR-discs, and I'll sell those as i'm not using them anymore. These are the rotors I bought, they are from a 1993-95 Honda CBR900RR.


s-l1600 (1) by Lars Krogh-Stea, on Flickr


They have the same PCD (78mm) as the original disks. That way I know I can drill and tap for them. The discs are offset 17.2mm. The original discs are offset 22mm, wich is a lot. I was hoping they were flatter, but I think I have aluminum slabs that are thick enough to make the spacers. Spacers would need to be about 1/2 inch thick, good news is that the lip that the disc rests on is protruding about 12-13 mm from the mating surface on the hub. that will create a solid base for the spacers. I'll countersink holes in the spacers for the original screws. Then I'll drill between the screws and tap the holes to fit the original honda screws (or, as I don't have the original bolts, I'll maybe buy cross drilled titanuim bolts) I have those for the Suzuki discs, but I'll sell those too. Next photo shuws the original hub. Should be easy to make spacers for this one:


2020-05-08_12-07-10 by Lars Krogh-Stea, on Flickr


I've also measured the original front axle and it is about four millimeters longer than the GSXRs. It is of course thinner, but I'll make new spacers and bushings in the lathe.


I'll paint the GSXR forks all black. I dont like gold forks on cafe racers like this:
cognito-fork-swap-5 by Lars Krogh-Stea, on Flickr


I want them to be like this:
honda-cb900-origin8or-10 by Lars Krogh-Stea, on Flickr


Of course there are also GSXR1000 forks with black inner tubes as well. They are awesome, but much harder to come by. I like the chrome inner tubes almost as much

[John Kat]

Be aware that the modern inverted forks are typically shorter than the oem resulting in less ground clearance.
On top of that the triples have less offset resulting in more trail made worse if you keep the 19" wheels.