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Help me with Carb tuning!!!

  • Thread starter Thread starter akreider
  • Start date Start date
Ok I got it running pretty good (no poppinp during decel) with #50 pilot fuel jets, 138 main jet, stock air jet, mixture screws at 1.5 turns and the eclip on the 5th groove of the needle. But now the bike only wants to idle at around 2000 rpm and I occassionally get little pop from the #4 carb. When I try to turn the idle adjuster down the bike will drop in rpms then die. I cant just turn it slowly to hit 1100 rpm. I made sure that the floats are set properly and that the throttle carble isnt hanging upl. Does anyone know how to solve this?


Adam
 
Did you try the 47.5 or go straight to the 50? Seems like quite a jump for pilot jets.
 
I tried the 47.5 but it was running way to lean. it was backfiring a lot on the decel.

Adam
 
I think that I will try them again because I adjusted the needles later to the 5th notch down. When I had the 47.5s in I had them on the 3 notch. Now that I think about it that backfiring would be attributed to the needle not the pilot fuel jets.

Adam
 
akreider said:
That is one thing I made sure not to do is to tighten them in, I only set them right when they touched.

Ok I have to admit my major lapse in thought while installing the jet kit, I didnt read the fine print that says to only change the air screws if it is running to rich. So I reinstalled the stock one earlier today and that solved the problem of the engine dying when twisting the throttle. The bike was just getting to much air. But I still have the problem of having to use the choke to keep the engine running. It will only run around 2000 rpm, I cannot back the choke off enough to get it to normal idle speed. I currently have the e-clips in the 2nd groove up or 5th from the top on the needle. I also have the 138 main jet installed.
Click to expand...
My 1981 GS 850 is having the same problem and seems to be getting worse. Won't run at all unless the choke is out. Runs great as RPM's increase while driving. Dies when I pull up to a stop sign. Hard to restart.
 
The problem that I found on my bike that caused the same symptoms was a small pilot fuel jet. But it was the wrong one because I had modified the intake and exhaust which leaned the engine out where the stock jets were useless. I solved the problem by switching in 47.5 pilot jets.

Have you done any modifications to the bike that would cause it to run lean? And can you idle the bike with the choke on?

Adam
 
I have to check one final thing tonight but it fires up right away when I press the starter button. And it runs great, but I did swap the 47.5s back in because it was idling way to high with the 50s. I will let you know how it goes.

Adam
 
It is running good now except for the higher idle. I will be getting new intake boots and exhaust gaskets soon. Hopefully that will fix the idling problem.

Adam
 
Sounds like synchronization. If one or more of the carbs shuts down 100% while the others are still at 99% because your sync is off, the bike will stall.
 
Ok I will try to get the carbs synced before I go ahead and buy those other parts. Thanks a lot for the help.

Adam
 
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