That Needle Thingy

[Anonymous]

Ok so I have dipped the carbs off of my 78 Gs750E. Now the bike has stock airbox with all new rubber pieces to the engine. It has a V&H pipe. The carbs have 120 main jets and 15 on the other jet. My question is when I was disassembling the carbs the needle that is in the slide is set at the middle (number 3) position. This is supposed to be stock. Now I have seen and been told that this should also move with the larger jet. Which way do i move it to richen and which way do I move it to lean the mixture. Do you move it towards the point on the needle to richen or lean. Thanks guys, lots of info on this site and many who know what they are talking about. Also got Robert Barr's o-rings the other day and they are the best package I have seen. It is nice that the guess work was taken out.

[Hoomgar]

Hey my friend. You move the clip down to "raise" the needle in order to richen the mixture. You would raise the clip to "lower" the needle in order to lean the mixture.

The needle regulates how much fuel is pulled into the emulsion tube so sitting it further in or closed is leaner and pulling it further out or open is to richen.

When you look at it this will make sense.

[duaneage]

Listen to Hoomgar, after 17 pages he knows all about needles and emulsion tubes.

[KEITH KRAUSE]

With just a pipe and stock air box with the lid still on, I think the 120 mains are too large. Maybe 112.5?
I'd take a plug read after a couple of miles at solid 1/3 throttle before adjusting the jet needle positions. Do what the plugs say. If it's a little lean you have your choice of lowering the e-clip to the 4th position from the top, or lowering the e-clip as I just said and then placing a jetting spacer (.023" thick) directly on top the e-clip. This would be like position "3 1/2". I'd probably try the 4th position first, but it depends on the 1/3 throttle test/results.
I'd also adjust the pilot fuel screws underneath OUT an additional 1/4 turn from where they were before the pipe. Then adjust the side air screws for highest rpm.
If you move the jet needles, you MUST re-vacuum synch these carbs.

[Hoomgar]

Listen to Hoomgar, after 17 pages he knows all about needles and emulsion tubes.

And I finally get to help someone else instead of asking for help myself