1977 gs 750

[Guest]

I have put a new kit in carbys. Set adjuster screws at 1 1/2 out, sync all 4 ,carby is sparkling clean inside . With air box on or off idles with chock but as soon as i touch the throttle it dies and shuts down, it is not flooding . Any advise will help. Engine runs smooth at slow chock or fast chock but push the chock in and it also dies.

[hannibal]

Check out the VM carb rebuild guide found here: http://members.dslextreme.com/users/bikecliff/

Even if the carbs look clean, there could be a blockage in one of the passages. Because it runs on choke but dies without it, it sounds like the pilot circuit isn't working properly.

Also, most people om this recommend keeping the OEM jets and just cleaning the jets as described in the guide mentioned above. You should replace thr O rings which are available here: www.cycleorings.com.

A cool trick I learned was to feel each exhaust pipe as the bike is warming up. The cold pipe will point to the carb that has a problem. This should be done without choke, or with as little choke as you can that still keeps the motor idling.

[Steve]

OK, which "adjuster screws"?

You have TWO screws on each carb. You mention 'airbox', so I will assume that is still stock, how about the exhaust? No matter, it does not change the mixture much anyway.

Start with the FUEL screw (the one on the bottom) between 5/8 and 3/4 turn out from LIGHTLY seated. The rule of thumb is to have the AIR screw (the one on the side) set to double the fuel screw setting, but I like to go just a bit less to provide a slightly richer mixture for initial tuning. Set the AIR screw between 1 and 1 1/4 turn out from LIGHTLY seated.

You may not need as much "choke" to start, but it should start rather easily, assuming the carbs are properly clean, valves are adjusted and ignition is up to par. When the bike is warmed up a bit, you can tune the mixture by turning each air screw OUT very slowly, listening for a decrease in engine speed. When you hear that drop in speed, turn the screw back in about 1/8 turn, move to the next carb.

When you are done, a blip of the throttle should give you a crisp increase in engine speed, followed by a quick return to idle. If the idle drops below set speed then comes back up, it's still too rich. If the speed hangs and returns slowly, it's too lean.

.

[albert]

THANK YOU FOR ALL ADVISE. i wrote everything down . made myself a tiny screwdriver with calibration marks on it and started adjustments.after about 15mins. WAMMMMMMMMMMMOOOO my 750 was singing.........it was like that moment in the movie SHAWSHANK REDEMTION when the opera singer was being played and every one stopped and listened. it was in the moment..........I was in heaven. thank you for all the help and advise regards Albert

[chuck hahn]

See post 43 in this thread. Depending on ENGINE number, there are different recommended mixture screw settings.

http://www.thegsresources.com/_forum/showthread.php?73723-Carb-OEM-specs-as-per-factory-manuals/page2