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Jetts

  • Thread starter Thread starter javamotorsports
  • Start date Start date
J

javamotorsports

Guest
Hello,

So I have a question, I bought a GS850L last year and had to rebuild the carbs. I dipped them and rebuilt them using the same size jet that came out of the carbs but I have always had a little stumble at about 1/4 throttle and sometimes at cruzing speeds you can slow down a little or power through it and it does fine. My question is the kit came with 180 and 190 jet. I currently have the 180 in should I swap them and do you think that will solve my problem? I am running stock everything on the bike. I love the old reto look.


Thanks for the help
 
So this is a 1980 gs850 with CV carbs? What brand carb kit did you use? stock main jet was likely 115 mikuni wise. 1/4 throttle is the tricky transition zone- have you tried fiddling with idle/air mixture screws?
 
Yes, I did try air metering adjustment but not much difference in performance. I also synced the carbs a couple of times. The jet I am talking about are the ones in the back of the carb at the inlet where the airbox hooks up. And it is 1980 GS850L with CV carbs
 
Sounds like it needs more gas. This is my cheap trick for CV carbs; Try running with your fuel cock in PRI, (The PRI position bypasses the diaphragm and supplies full fuel to the carbs without the need of vacume, I have found this position to be helpful also when cold starting a GS after the bike has sat for a day or more.) You may also while you have the tank off, if needed, disassemble and inspect your vacume assisted fuel cock, to eliminate the possibility of your vacume operated petcock not functioning properly and starving your carbs of fuel. With all that out of the way, Try going up one size on your slow jets this will help from idle to 1/4 throttle, smoother idle and easier starting also, if it still stumbles disassemble your slide, relocate the nylon washer from your needle jet from the top of the eclip and put it on the bottom of the eclip between the spring washer and the eclip, Reassemble the slide, then turn the needle with your fingers until you feel the detent from the top nylon part drop between the open ends of the clip so the needle is straight, this will give you more fuel in the mid range 1/4 to 3/4 throttle. you could also try drilling some holes in your air box to increase air flow but be careful about doing nonreversible changes, but you can always put the holes in an area where you can make a plate to cover it back up or even partially cover to experiment with different opening size.
I did the needle trick on two of my gs 650 gl bikes and it was a good improvement with no part purchase required, one of them I installed 1 size up on slow jets and the other I kept the stock slow jets, the difference is the one I sized up on slow jets will start easier with less choke, and idle lower and smoother than the one with the stock slow jets.
I also adjusted the factory set air fuel mixture screws.
I hope this helps, Good luck.
 
Those 180 and 190 jets are the PILOT AIR JETS, not the main jets. They control the pilot mixture, the 180 will give you a slightly richer mixture, so leave that one in there.

Your stumble could also be from not having enough of that mixture at low-throttle or it could be that the needles need to be raised a bit. Not much, for a stock bike, but they did come from the factory a bit lean.

.
 
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