Restoring a '75 GT750!

Photos and progress of your restorations, even bikes you had but no longer own.

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Toast
On the street
Posts: 22
Joined: Sun Oct 14, 2012 8:28 pm
Country: United States
Suzuki 2-Strokes: '01 Dr650, '75 GT750

Re: Restoring a '75 GT750!

Post by Toast »

Hey guys, I haven't posted on here a while... I'll have to catch up sometime. Anyways, I've got the bike running again but I'm having difficulty syncing the carbs (again its a 1975 "M" model). I tried the method of disabling 2 of the cylinders while getting the one to idle @ 1000rpm and so on. Correct me if I'm wrong, but you do this with the Idle stop screw (big knob) for the right carb and the little idle stop screws for the center and left. My problem is that once I get all three idling individually @ 1000 and hook all three leads back on, the bike idles @ around 2500rpm. To solve this I turn down the big knob (which undoes the adjustment for my right carb) and it screws up the sync. I can tell that right cylinder runs poorly and I have lots of vibration between 1500rpm and 2000rpm. Maybe I'm missing something painfully obvious but is there a way to adjust that right carb without touching the big knob?
pearljam724
AMA Superbike
Posts: 1681
Joined: Tue Jul 24, 2012 11:45 pm
Country: U.S.
Suzuki 2-Strokes: 75- GT 550 / 76- GT 750
Location: SW PA

Re: Restoring a '75 GT750!

Post by pearljam724 »

Did you adjust the butterfly valves ? They need to open and close in synch with one another. If that's not right, everything will be out of wack.
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RING_DING
To the on ramp
Posts: 447
Joined: Thu Apr 21, 2011 5:32 am
Country: USA
Suzuki 2-Strokes: 1974 GT750 B-4 (JDM), 1975 GT750M
Location: North Carolina

Re: Restoring a '75 GT750!

Post by RING_DING »

Toast,
The large adjustment screw on the right carb controls all three together so it won't "de-synch" your carbs if you turn it. After you've adjusted and set each carb using it's individual adjuster, then use the large adjustment screw to back it all down to 1000/1200 RPM. I've used this method several times and I've found it to be pretty accurate. I hook up a vacuum gauge after all this just to check. If your bike is still running poorly after you've done all this then I suspect it is something else.
1973 Suzuki GT750K with Sidecar - Bonneville 2020
Toast
On the street
Posts: 22
Joined: Sun Oct 14, 2012 8:28 pm
Country: United States
Suzuki 2-Strokes: '01 Dr650, '75 GT750

Re: Restoring a '75 GT750!

Post by Toast »

Ring-ding, yeah, I see what your saying. So I guess I'm hunting another issue. I'll check throttle plates. I also have the newtronic ignition but can't find a good description of how to time it. Anybody have a link for that?
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