Mixture adjustment screw?

[liverchip]

Hey guys. My 163 motor has the common slide/needle carb. What is the consensus on the function and proper adjustment on the underside-front adjustment screw(the one which needs to be turned with a very short screwdriver).I am running at 3500ft with stock exhaust and 2 turns on this screw. The plug is grey, so I'm assuming she's running lean. I've checked the needle clip position and found it (the clip) at its highest groove(needle farthest inserted). Since very little of my riding thus far has been more than half-throttle, I assume I must richen this puppy up using the clip and that funky screw. Long-winded I know, but what's the consensus on that screw?

[cycleway4]

hi....i would richen it up using the clip....drop it down the needle at least one, maybe 2 positions..............

the idle mixture screw is just what it says.....an IDLE mixture screw....
it will have very little, if any, effect once you touch [open] the throttle.
The idle mixture screw is ported into the idle, slow speed jet, and enters into the engine in front of the slide................the correct operation of this circuit requires the slide being in the closed position.....once the slide is raised, your engine goes to running off the main jet/needle jet fuel circuit

[ob1]

On my Lifan carb, and the Keihin it copies, the idle screw is simply a pin to hold the slide open at a given point to maintain idle speed. The pin rides in a wedge shaped cut on the slide.

Your needle does sound like it is in a lean position. I would place the clip in the center groove then evaluate.

Moving the clip towards the pointy end richens the mixture.

[sheadouglas]

Lots of people seem to be adjusting their carb, and moving the clip down. Should I do this if the bike is running just fine? How will I know if I should ever have do this?

[fatboy250]

Lots of people seem to be adjusting their carb, and moving the clip down. Should I do this if the bike is running just fine? How will I know if I should ever have do this?

If you make any mods to your air filter or exhaust, OR if your's bogs down when you crack the throttle open during slow roll on acceleration. OR if you have backfiring during decel. The old spark plug test is applicable too.

Jason

[sheadouglas]

I might get one small backfire or pop at only high RPM's. What I mean is when I run up the RPM's and let off, I get a POP. That's it.

[liverchip]

The only reason I'm messing with it is a stumble when moving from idle to wide open throttle.

[fatboy250]

If you've made any mods to increase air flow, you'll need to enrich the mixture. I believe most of these are on the lean side from the factory to meet EPA requirements. So, if you make a mod to increase air flow, it's only gonna get leaner.

Ours are 2 1/2 turns out with K&N type filters and exhaust baffles drilled.

Jason