1981 gs750 (gs750e) Retro Racer project

[LarsKroghStea]

Found a good rebuild tutorial online:

https://thexscafedotcom.files.wordpress.com/2014/06/mikuni_bs-cv_carburetor_rebuild_tutorial.pdf

2019-06-09_11-33-11 by Lars Krogh-Stea, on Flickr


2019-06-09_11-33-00 by Lars Krogh-Stea, on Flickr


Stupid as I am, I didn't bring the carbs home with me. I'll make some tube adaptors for the drainholes while I wait for my next wrenchday..

[LarsKroghStea]

I'm learning a few things about carburettors today..


The hoses I thought were overflow-circuits are really just for venting. The reason for connecting hoses to them is so gas will flow away from the engine in case of a crash where the bike is left lying on the side. Makes more sense since they're located so high up.


The leftmost hole on the intake side is the real vent and is where gas will overflow. I guess that points to the float/needle.


2019-06-10_12-50-50 by Lars Krogh-Stea, on Flickr

[LarsKroghStea]

I've also read page 4-5 and onwards in the workshop manual for an explanation on why gas flows from both holes, so I'm now confident I have it narrowed down to wrong float setting or some obstruction or similar problem connected to the needle not making a good enough seal to stop the gas from flowing.

[cowboyup3371]

Quit reading that one and get Nessism's CV rebuild tutorial from Basscliff's site. It is a much better written one.

http://members.dslextreme.com/users/bikecliff

[LarsKroghStea]

Quit reading that one and get Nessism's CV rebuild tutorial from Basscliff's site. It is a much better written one.

http://members.dslextreme.com/users/bikecliff

A million thanks yous! I've never scrolled past the manuals section of that page. I now see that it's a gold mine of information

EDIT: It's the same tutorial that I've got from somewhere else. But thanks for showing me the rest of the site

[LarsKroghStea]

This is a picture of how my bike was assembled. Some kind of thick radiator hose sits loosely over the intake boot and carb opening.


48036867868_135740661c_o by Lars Krogh-Stea, on Flickr


Next picture shows my brothers bike (same model and year). This is an airtight assembly:


riktig_muffe by Lars Krogh-Stea, on Flickr


My bike is sucking in lots of unfiltered air and at the same time the intake plenum is not alowed to do its job as it's supposed to. Next picture shows one of the intake boots. It's inside diameter is about 45mm and on the carb the outside diameter is about 53mm. Not an optimal solution..


feil_muffe by Lars Krogh-Stea, on Flickr


They don't make a particularly tight connection with the holes in the plenumbox. This is also why gas poured over my engine.. If everything was done correctly, excess fluid would flow out the boots and down the draintube in the bottom of the plenum. One less firehazard to worry about when this is corrected Guess the bike will run smoother as well.

[LarsKroghStea]

New carburetor boots. Ordered the original Suzuki ones and the rubber seems brand new 😊


2019-06-30_06-42-06 by Lars Krogh-Stea, on Flickr


I took apart the carbs and cleaned the float needle and filter. Now there's no leaks and the fuel level is correct when measured through the clear hose.


2019-06-30_06-44-39 by Lars Krogh-Stea, on Flickr


I also took the oppurtunity to change the rail bolts into unbrakos:


Untitled13 by Lars Krogh-Stea, on Flickr

[Buffalo Bill]

4 years and your bike ain't rideble yet???
I can't take your project as serious…

[LarsKroghStea]

4 years and your bike ain't rideble yet???
I can't take your project as serious…

Qurious to know the chain of thoughts leading up to that post.. I think I've explained this more than once..
Or are you just angry because you spent your time reading a few posts and now the ending isn't in plain sight?

[Buffalo Bill]

Qurious to know the chain of thoughts leading up to that post.. I think I've explained this more than once..
Or are you just angry because you spent your time reading a few posts and now the ending isn't in plain sight?

Maybe my bad. Right, I just read the last few posts and looks like you've never had the bike on the road.
You titled this thread retro racer, so are you racing the bike?

[Nessism]

Be sure to only use the type of fuel filter that flows with a gravity feed system. Many of the paper type filters cause a restriction. In the USA the gravity feed system filters are for lawn mowers and machines like that.

Keep going, you are doing a good job...

[LarsKroghStea]

Maybe my bad. Right, I just read the last few posts and looks like you've never had the bike on the road.
You titled this thread retro racer, so are you racing the bike?

No problem I bought this particular bike because my Brother has the same model.

My brother and I live about 3,5 hours apart and our father lives somewhere between. A little over an hour from my house.
The bikes are in his basement, and we meet up at his house once in a while to work on them. The bike was in OK running shape when i got it.
I rode it the first summer and the i picked it apart to rebuild it. The project, for me, is more about building than riding. Everytime I'm close to getting it on the road some new idea pops up. This summer, however I'm putting it back on the road as a friend of mine got his motorcycle license, and we're planning som daytrips around here.

If you read more posts you will find that much time is spent how the different parts will look and how I'm going to make them. The rearsets for example is CAD drawn and made by me on a CNC router. The pegs are made by me on a lathe. Both are stuff I had to learn while i was doing it. The seat is the first part that I've ever welded, and the seat I made on my wifes sewingmachine wile looking at a youtube wideo. My 13 year old daughter showed me how to thread the machine. I've also built the weels from OLD and new parts and powderdoated the parts with I kit I bought. I've recently bought an anodising kit, and when the top triple is finished I will anodise it and the rearset and write text on them with a laser engraver a friend of mine has. So you see, it's more about the process than the end for me.

But as I said, it will be on the road in a few weeks, so if you're interested, just follow the thread.

For the racing part, it's only inthe name. I thought it would be wrong to call it a cafe racer, so I came up with something similar that I think sounds cool

I also have a GSXR750 USD fork with Yamaha R1 brakes that I'll finish together with Cognito moto front wheel next winter.

[LarsKroghStea]

Be sure to only use the type of fuel filter that flows with a gravity feed system. Many of the paper type filters cause a restriction. In the USA the gravity feed system filters are for lawn mowers and machines like that.

Keep going, you are doing a good job...

Thank you And I'll keep in mind the info about the fuel filter.

[LarsKroghStea]

First test run on the road. Tank and seat are stowed away until all the wiring and cables are routed correctly. I'm quite happy with the seating position. Work done today is; 520 conversion, mounting brakes, throttle and clutch. Next time is carb tuning After that cable routing and finishing.

[LarsKroghStea]

Btw, I have a Kerker 4-1 exhaust on. Anyone knows what kind of gaskets I need for this?