New member, carb jetting

[Mark Crystal]

Hello all,

Had a couple questions. I bought this bike (my first) 1977 gs 750 I'm learning more an more as I read. I bought it for 350$ didn't run. I replaced points and gapped correctly. It has pod air filters and I'm unsure if they put a jetting kit on it. Got it running, cleaned the carbs. #3 cylinder exhaust is cooler then all the rest. And where does the vacuum to the petcock go? #3carb? Currently not connected. Won't go over 55 just bogs. What should the jets on the bottom be set at? 1 full turn? And I have the top air jets set at 1and a quarter. Any help would be greatly appreciated.

[Steve]

First of all,


You will need to verify that you have main jets that are a bit larger than stock, if you wish to retain your pods. I believe the stock main jets were 100s, you will want something in the vicinity of 110, but that is just a guess.

Having the pilot fuel screw (the one on the bottom) turned out one full turn is probably a good place to start. As a rule, you start with the air screws (the ones on the side) double the fuel screw setting, then adjust from there.

HOWEVER, you will probably be doing yourself a BIG favor if you do a proper freshening up of the carbs with a full "strip and dip" cleaning and replacing all the o-rings with a kit from cycleorings.com. You should also plan on changing the intake boot o-rings and the lousy screws that hold the boots to the head. The good news is that ALL of the o-rings and the replacement stainless bolts are less than $25. Do NOT get any carb rebuild kits. The parts in them are usually of inferior quality, and don't even contain everything that you will need to clean and rebuild the carbs. Your current brass pieces (all the jets) should clean up just fine, ready for re-use.

Our official greeter, BassCliff might be along shortly with his full "Welcome Package", but he usually notices new members quicker if you do an introduction in the GS Owners forum.

.

[ender22]

Vacuum to the petcock goes on carb #3.

Using an aftermarket petcock without the vacuum switch.

I synced the carbs the realized i had left it open, After re-attaching this is what the gauges showed:


And then corrected:


This would definitely be why #3 pipe isn't hot.

[Mark Crystal]

Thanks for the speedy reply. I have yet to make a manometer like the one in the photo. I have all the parts just need to put it together. Ill try what you suggested and see what happens. Thanks so much!