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VM26mm Carb Question 78 GS1000E (Mystery problem)

  • Thread starter Thread starter vintagemcycleguy
  • Start date Start date
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vintagemcycleguy

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I rebuilt the carbs on my 78 GS1000E last summer. I orinally had a problem with the idle flucuating and the bike boging down when getting on the throttle so I suspected an air leak somewhere, I relaced the intake boots and installed new o-rings, and than made sure the air box boots were in good shape and installed on the carbs correctly. I still have the same problem with the idle. I also sprayed a liquid on the boots to look for leaks and found none. Now the air screws on the side and also the fuel pilot jet screws underneath adjust or turn very easily. I checked to make sure all the o-rings on both sets of jets were there and they are. Is it possible that the o-rings are bad to the point where they allow air into the system to cause my problem either through the air screws or the fuel screws. What'll ya'all think, thanks.
 
Re: VM26mm Carb Question 78 GS1000E (Mystery problem)

Assuming you have stock airbox/filter element, carb jetting and exhaust system.........................

On the fuel inlet valve in each float bowl......The insert the inlet needle fits into is removable and a press fit. Underneath that insert are "O" rings. Did you replace those? If they are leaking, and if they are original, .............they will be leaking, :-) fuel will seep even when the needles are in the closed position causing a too high level in the float bowls and boggy running.

Where did you get the replacement "O" rings. The sizes needed are precise and auto store look alikes will not work. I have used my share of the "O" ring kits from Robert Barr and I have to say, they are perfect. :-)

Did you soak the carb bodies in carb cleaner overnight? Spray cans are useless for anything more than blowing out passageways after the carbs have been cleaned/dipped.

Did you set the float heights to specs?

Did you synch the carbs with vacum guages/carb stix?

Earl




vintagemcycleguy said:
I rebuilt the carbs on my 78 GS1000E last summer. I orinally had a problem with the idle flucuating and the bike boging down when getting on the throttle so I suspected an air leak somewhere, I relaced the intake boots and installed new o-rings, and than made sure the air box boots were in good shape and installed on the carbs correctly. I still have the same problem with the idle. I also sprayed a liquid on the boots to look for leaks and found none. Now the air screws on the side and also the fuel pilot jet screws underneath adjust or turn very easily. I checked to make sure all the o-rings on both sets of jets were there and they are. Is it possible that the o-rings are bad to the point where they allow air into the system to cause my problem either through the air screws or the fuel screws. What'll ya'all think, thanks.
Click to expand...
 
You could also make sure that you did not break the point off the mixture needles, (botom side)
 
Where are the pilot fuel screws set? Stock bike should be about 1 turn out. That may still need fine tuning but if about 1 turn out then that's not the cause of a fluctuating idle.
Have you set the side air screws for highest rpm and re-set to about 1,000 rpm?
Are the two floatbowl vent lines clear, routed under the seat area and for sure not kinked?
Timing advance mechanism lubed and operating freely? If you have one of those old Martek ignitions, is the set screw tight on the magnet/collar? If the set screw backs off, the collar will spin and the rpm's will hang and do funny things.
 
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