OK all, I;ll try to keep this as short as I can. 
(79 GS750EN)
Been experimenting with carb settings. It seems almost everyone
(self included) has at times had setups that made the bike hard to start, or required very long warm up times before the engine would accept throttle. There have been complaints of flat spots in the transition from idle to higher throttle settings. Other problems have been poor gas milage, fouled plugs, lean plugs, popping in the exhaust, preignition, overheating and the engine sounding like Buuuuuu when throttle is quickly turned in midrange. None of the books I have give a base setting for the pilot screw, and none of my books give a vacum value for the rpm they say the carbs should be balanced at.
When I rebuilt my carbs, the paint/seal on the pilot screw was unbroken. The pilot screws were set at 7/8th's of a turn out.
I have used many different combinations of settings and vacum that resulted in a smooth running engine, but I have not found settings that result in everything being perfect at the same time.
The objective is easy starting with minimal need of choke, minimal warm up time before the engine will accept throttle, smooth transitions throughout the throttle range, good power output throughout, clean burning plugs, reasonable gas milage, and a cool running engine. The jetting, mufflers/pipes and airbox are stock. Presently, I am using 1 turn out on the pilot screw, 1 3/8 turn on the air screw and am drawing 23 inches of vacum at 2000 rpm. with these settings, starting is instant with half choke/enrichener, warm up is about two minutes, throttle transition is very good, power is excellent throughout the throttle range with no flat spots. Bad news is plugs burn very dark (I know ...too rich) and gas milage is down from 50 to 46 mpg.
It would be helpful to know what everyone else is using for mixture and vacum settings and what characteristics those sett
ings result in. thanks....
Earl
(79 GS750EN)Been experimenting with carb settings. It seems almost everyone
(self included) has at times had setups that made the bike hard to start, or required very long warm up times before the engine would accept throttle. There have been complaints of flat spots in the transition from idle to higher throttle settings. Other problems have been poor gas milage, fouled plugs, lean plugs, popping in the exhaust, preignition, overheating and the engine sounding like Buuuuuu when throttle is quickly turned in midrange. None of the books I have give a base setting for the pilot screw, and none of my books give a vacum value for the rpm they say the carbs should be balanced at.
When I rebuilt my carbs, the paint/seal on the pilot screw was unbroken. The pilot screws were set at 7/8th's of a turn out.
I have used many different combinations of settings and vacum that resulted in a smooth running engine, but I have not found settings that result in everything being perfect at the same time.
The objective is easy starting with minimal need of choke, minimal warm up time before the engine will accept throttle, smooth transitions throughout the throttle range, good power output throughout, clean burning plugs, reasonable gas milage, and a cool running engine. The jetting, mufflers/pipes and airbox are stock. Presently, I am using 1 turn out on the pilot screw, 1 3/8 turn on the air screw and am drawing 23 inches of vacum at 2000 rpm. with these settings, starting is instant with half choke/enrichener, warm up is about two minutes, throttle transition is very good, power is excellent throughout the throttle range with no flat spots. Bad news is plugs burn very dark (I know ...too rich) and gas milage is down from 50 to 46 mpg.
It would be helpful to know what everyone else is using for mixture and vacum settings and what characteristics those sett
ings result in. thanks....
Earl
