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More Carb Trouble - Pilot (Fuel) Screws

  • Thread starter Thread starter justanother54321
  • Start date Start date
J

justanother54321

Guest
I have been told in another posting, that all the pilot (fuel) screws on the mikuni vm26ss (GS850 77-79) are the same . The rebuild kit that can be bought for the carbs has only one pilot screw size. However, on my carbs, the new pilot screws only fit 2 of my carbs. There other two carbs need shorter needles.

I tried to put the new needles in but they would only thread
About 1.25 turns before they were all the way in and poking up through the carb body?

Does anybody know why this is the case?

Are there other carbs out there that were on slightly different GS models that could have been put on my motorcycle by a previous owner?

Or are the pilot (fuel) screws actually supposed to be different on half of the carb rack (two long, two short)?


Other Questions:

What constitutes "1 turn"? Does that mean twisting the screw 180 degrees, or going a full 360 degree revolution?

Also, below are the Specs for my carb setup. What does "5/8 turns out" mean for the pilot (fuel) screw?

GS850 (77-79) the specs are for the VM's

idle r/min........... 950-1150
carb................... mik vm26ss
id no................... 45060
bore size ............ 26 (1.0)
float height ......... 23-25. (0.91" - 0.98")
fuel level ............ 3.0 - 5.0 (0.12" +/-0.20")
pilot air screw ..... 1.25 turns out
pilot screw........... 5/8 turns out
pilot air jet........... 1.2
pilot jet............... #15
cut away............. 1.5
jet needle........... 5DL36-2 (the -2 2nd notch)
needle jet .......... 0 - 6
pilot outlet........... 0.6
by pass ............. 0.8
main jet............. #102.5

Any help sorting all this confusion out would be much appreciated.
 
One turn is 360 degrees.

5/8 turn means that you screw in your pilot mixture screws until they seat VERY LIGHTLY. Then turn out the screw 5/8 of a turn. Which means one half turn plus another 1/8 turn.

You do have pilot AIR screws as well which are on the side of your carbs. The mixture screws are underneath. Is there some confusion there perhaps?
 
The fuel/mix screws should be the same. unless some one has been micky mousing things. Could their be a broken piece in the carb ? Their are also two different needle styles one point one blunt
Their is no 77,78 GS850 79 first year for the 850. GS1000 came out late 77
 
Last edited:
Thanks for the explanation on the turns. I am definitely don't have the pilot fuel screw and the pilot air screw mixed up. Pilot fuel is on the bottom. Pilot air is on the side.

.... I am still hoping someone can explain the variation in sizes of the pilot fuel screws that I have on my set up... I may just take a picture to show everyone... But it also isn't that big of a deal since I already started rebuilding two carbs from another carb set, to replace the two carbs that won't take the longer pilot screws....
 
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