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Old 10-03-2012, 09:48 AM   #6
disston's Avatar
Joined: Mar 2011
Location: Silver Spring, Md
Oddometer: 10,235
They are both 40mm carbs. The 114 is an RS carb with a needle jet size 2.66 ; the 107 is an S or RT carb with a needle jet size 2.64 ; Other than that difference the two carbs appear to be identical. That is comparing the jet and other sizes listed in the Bing manual. In operation this small a difference in needle jet size would not be noticeable, I think.

Both jet needles and needle jets are wear items. The needle jet is the jet that sits on top of the stack in the center of the carb. The jet needle hangs into this jet. I know it's confusing but we are talking about a needle called a jet needle and a jet called a needle jet. The jet needle rubs a bit against the needle jet and this causes wear as the needle is rubbing up and down. Bing recommends changing these two parts at only 25K. Some of the mechanics have much higher mileage expectations from these things. I have changed the two pieces in my R90/6 and with, maybe, 35K on them I thought there was a small improvement. But really it's something that is hard to feel with the Butt Accelerometer.

The PO may have already done this. If not just get both sets so you have matching carbs. On most parts fisch you can find the numbers for the size jets you want. The needles BTW are the same here and they are both on notch #2.

Some other numbers you may want to check;

Main jet 160
Idle jet 45
Idle mix starting point is 1.25 turns out
Clip position is #2

There are other things mentioned in Bings manual but these items are sometimes messed with by owners. The items above, like I said, are the same in both carbs, or should be.
Never memorize something you can look up.
---Albert Einstein

Pay your debt, piratejohn.
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