Fuel mixture screw

ENFORCER4 · May 18, 2004

Hello All,

The other day I reset my idle adjustment on my quad to run at aproxametly 1,800 rpm. Then tried to adjust my mixture screw and it does not make much difference if it is screwed out almost all the way or nearly all the way in.

The only increase in rpm that is noticeable is at approxametly 1/4 of a turn or less out. then it increases very little, maybe 200 rpm

How sensitive should the fuel mixture screw be?

Is it possible that it needs to be bigger/smaller?

Please keep in mind that I am not very educated on carbeurator's so explain as well as possible!

And as always thanks

coronaberg · May 18, 2004

mixture

Idle mixture screw is for idle speed mixture thats all. At that RPM you are on the transfer port.Different jet.

LINEAWEAVER · May 21, 2004

Hi Cory,
If you truly have the need to feel the idle rpm fluctuate while adjusting the mixture screw simply lower the idle rpm and / or drop the metering rod down. (Note: The later may cause a bit of a lean condition during acceleration)

Larger slide openings (ie high idle) = less pilot circuit influence.

If it starts good, idles smooth and runs well your settings are near perfect regardless of the pilot screw turn count.

Please keep in mind that the X1 camshaft does provide for a racy idle and does not take kindly to excessive tick-over (ie more than a couple of minutes).

Hope this helps.
Kind Regards,
Dale

Ps
All else remaining equal you can alter the slide cutaway and / or change the pilot jet size to bring the pilot screw into a more neutral setting. However, your idle mixture will end up being the same only now the screw count is different. (Note: this will also require you readjust the metering rod and overall may prove less than perfect during initial start up and / or rapid acceleration)

husabutt · May 21, 2004

Just to expand on this topic a little. If the bike will not idle at a high enough RPM, even with the idle screw turned in all the way, would this indicate a too small pilot jet? My 97 600fx will just barely idle and the idle screw is in all the way. Other than that it carburates fine.

Thanks

LINEAWEAVER · May 22, 2004

Hi Husabutt,
A worn slide and / or throttle stop screw will cause such a condition as will any number of variables.

May I suggest:
Using the throttle cable slack adjustment provisions raise the slide to establish a suitable idle speed. If the engine responds favorably and properly returns to idle from acceleration then simply raising the throttle valve via a longer stop screw and or new slide will be the fix. However, If the engine wishes to hang up and / or has a fluctuating idle then mixture adjustments (ie Pilot jet, metering rod and slide cutaway) are likely in order.

Hope this helps.
Best Regards,
Dale

husabutt · May 22, 2004

Thank you!

Fuel mixture screw

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