Back Into Bikes, '77 GS750 Project

[Zerospirit]

The favorite front springs are Sonic Springs, a straight rate setup that aren’t bad while Hagon is still a good choice for the rear.

Thanks! I'll look into that once I get this thing running.


I dropped the frame over the engine. Is there a better way to do this? Frame got a little scratched but it can be touched up.


Got most everything put together.


I kind of just realized it but this is a really good looking bike compared to most of todays offerings.



OK, so I tried to start it. Good news, starter motor works. Bad news, it doesn't run. I had it running for like 5 secs but I had to spray fluid through the carb intake. I also noticed only #1 and #4 exhaust pipes were hot. #2 and #3 were ice cold. I tried starting it with the airbox on and that didn't help.

Hmm... OK, checked spark and they are all sparking. Removed the float bowl drains and there is fuel in there. Yes, I did use new fuel. I know I set timing correctly. Triple checked it.

Next up is compression test. The numbers I got were:
#1 60 psi
#2 55 psi
#3 30 psi
#4 30 psi

Seems really low and not even. I also noticed that when I put my hand over each carb intake, 1-3 has a strong sucking while number 4 barely sucked.

Any ideas? Also another thing to note, it sounds very healthy when cranking over. Maybe I should double check valve clearance?

[Grimly]

Did you lift the barrels and hone the cylinders? A new set of rings might have been nice, too.

[oldGSfan]

I use a 1 ton chain hoist and straps, makes suspension and tire work easier too. I put the engine on its side on a cheap furniture dolly with a moving blanket on it.

I dropped the frame over the engine. Is there a better way to do this? Frame got a little scratched but it can be touched up.

[roeme]

(...)

Next up is compression test. The numbers I got were:
#1 60 psi
#2 55 psi
#3 30 psi
#4 30 psi

Seems really low and not even. I also noticed that when I put my hand over each carb intake, 1-3 has a strong sucking while number 4 barely sucked.

Any ideas? Also another thing to note, it sounds very healthy when cranking over. Maybe I should double check valve clearance?

That's way too low. IIRC, those should read between 120-180 psi, lower limit being 100, and maximum difference between the cylinders around 28 psi.

[Zerospirit]

I am a dum dum. Timing is off. Crank is set to T and this is how the cams look. Intake (left) is pointing up and exhaust is pointing down. They should pointing right at each other. With 20 pin links in between. Got that fixed and maybe it will run now. I didn't try to start it yet.


Started rebuilding the brakes. Here's the front caliper. Brand new OEM rebuild kit. Even came with a piston although the old one is still good. New EBC pads.


Rear caliper. Couldn't find an OEM kit. But I hear good things about K&L. New EBC pads.


Rear master cylinder. Holy moly! Thats all the gunk that came out of it. This one also got the OEM rebuild kit.


Front master cylinder, I just got a brand new universal one. I'll have to wire in the front brake light switch as it is a little different. I am still waiting for my new stainless steel brake lines from the UK. I should have just made my own...


And with the permission of the forum admin, I made a few stickers.


For scale.

[Zerospirit]

Rolled it outside again.


And it does run! Fixed timing and adjusted the points.

https://www.youtube.com/watch?v=RpL509hmtaw

Huge progress for me there. I was really starting to question if this project was worth it. But hearing it start up like that, it is. Yes, I will install the OEM airbox.


Now this next part... Yeah, I got more. I didn't plan on getting more bikes. But this was too good a deal to pass up.






This blue one is very nice. Everything works and runs/rides great.


Video of the blue bike.

https://www.youtube.com/watch?v=VPUJSysc_4A

Funny thing is, I actually owned that red bike like 8 years ago. The build thread might still on this forum.

The blue bike only needs cosmetics and probably new rubbers. Runs and rides great.

The red one needs work. A bit stumbly so probably needs a carb cleaning. But the gearbox is hard to use. Hard to find neutral. Also needs paint.

As if I needed more projects haha

[steve murdoch]

Congrats on the new bikes.
The GS addiction is strong!
The stock exhaust on the blue looks great.

[bobgroger]

The new bikes have not been ridden enough lately. Glad to see they went to a good home. I still have the Banditized '80 1260
Allen, the carbs on the red bike were off the 1260 when I put the RS carbs on so probably jetted way wrong. I can give you the 34mm carbs back if you want to clean them....

[Zerospirit]

The new bikes have not been ridden enough lately. Glad to see they went to a good home. I still have the Banditized '80 1260
Allen, the carbs on the red bike were off the 1260 when I put the RS carbs on so probably jetted way wrong. I can give you the 34mm carbs back if you want to clean them....

I’ve had these Mikuni RS34 laying around. Wonder how well these would work on the red 1100. I’ll try these first.


I only rode the blue one around the block when I got them to the shop last night. I’ll ride it more today.

Super excited to get started on these. Gonna be painting this winter. I'd love to take these 1100 on a good tour.

[GZ3]

Yes there's an easier way to install the motors just pick em up and put em in.

Great job getting it back together