carbs sync'ed, still runs poor

[Guest]

I was able to synch the carbs a lot easier after I found out that I left the airbox to carb clamps loose. Until I tightened these I was chasing synchronization. Now that the clamps are tight and leaks checked for with propane and the throttle synch'ed the bike is still running with a sputter when cruising. If I am accelerating it seems fine, but you can only accelerate for so long.

I have:
soaked the carbs in berrymans for 2-3 days
scrubbed with nylon brush
shot carb cleaner through all passages
replaced float valves
rejetted to factory
factory airbox
delkevic 4 into 1 exhaust (they say you don't have to rejet)
followed "CV Carburetor Rebuild Tutorial" by Nessism
followed "Adjusting Idle Mixture, Using the Highest RPM Method"
on setting the idle mix, #3 didn't do much when I screwed the mixture screw all the way in, but it did make a change when I got it to about 3.5 turns out (engine speed picked up and smoothed out).

[Nessism]

How's the foam on the factory air box end caps? Did you replace the carb boot O-rings? Does the idle hang suggesting a lean condition?

The midrange jetting is lean on many GS bikes so you may want to consider lifting the needle to counter that. Instructions on what to do in the carb rebuild tutorial.

[greg78gs750]

presumably you replaced all the carb orings?

[jdion81]

I guess, I left that out, I have put window foam on each end of the airbox and put foam sealing the rim of the air filter element to the top of the airbox. I have also replaced the intake boots between the head and carbs as well as new O'rings from cycle o rings. I have also installed new boots from airbox to carbs.

I'm not sure of idle hang, do you mean when the throttle is twisted and let go, do the rpms stay high instead of dropping to idle speed? If so, I'll have to recheck, but I was thinking that was not happening.

[jdion81]

I also replaced all carb o rings from cycle o rings.

[Gorminrider]

The bike should be running pretty well BEFORE you do a carb synch- carb synching is a "fine point" done after every other thing is known to be very close to "good". Bike should run pretty well with just a bench synch of throttle butterflies + valves checked+ carbs clean+ air mix set +ignition good.

#3 idle air mix is an indicator that that passage is not clean or that something is wrong at needle .
Fuel flow could also be the problem-floats
etc etc

A carb synch won't fix "issues". If you try to tune out issues with it, you will end up going in circles .

[jdion81]

The thing is it does run pretty well at an idle, in fact it's rideable the way it is just kind of a pain in the rear the way that it does run.

[jdion81]

https://youtu.be/YIWe367UJEA

[jdion81]

Woohoo, that did it. I pulled the slides and removed the plastic spacer and replaced it with (3) 3mm washers. Now it runs like a scalded dog. I may revisit the idle mix though.

I did find that 3 of the carbs were original set up wrong. Had been that way since I bought the bike. When cleaning and rebuilding the carburetors I decided not to dig into the slides since I didn't have a set of snap ring pliers that could reach into the retaining ring. I guess I should have done that. Hindsight is 20/20. Interesting though, the one that was set up correctly was the number 3 carburetor.

Thank you Nessism for the direction.