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Post by zummerp on Mar 2, 2018 17:01:24 GMT -5
Hey guys - I just replaced my first carb today on a GY6 50cc with BBK. Everything is working well with 1 exception - my idle is too low and the idle screw is completely tightened. How do I fix that?? Should I loosen it completely and attempt to move the throttle cable? I’m at a loss on this one! Thank you all for the help!
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Post by dexameth on Mar 2, 2018 17:34:01 GMT -5
Screwed all the way in! No, no.
If it's all the way in, turn it out 1 and a half turns. Then start the scoot and turn the idle speed screw to get it humming along but not moving the back tire. Let it warm up.
Then, turn the idle screw out a quarter turn and listen for a few, see if the RPMs raise or lower. This will take a few minutes of listening close. Your RPMs should raise as you turn it out each time.
You'll get to a point where the RPMs will start to drop again. Stop, now turn it back in one half turn.
Now adjust your idle with the idle speed screw to a happy idle.
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Post by lilpinny on Mar 2, 2018 17:34:27 GMT -5
The cable should have adjusters on it so you can tighten it. You also should be able to tighten where it plugs into the carb and on the throttle. Loosen your idle screw to about halfway and make the adjustments
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Post by lilpinny on Mar 2, 2018 17:53:38 GMT -5
In the middle of the cable you'll find a lump that you can uncover . Those are the adjustment fine tuners
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Post by GrumpyUnk on Mar 4, 2018 1:11:07 GMT -5
Actually, the idle screw on the carburetor has zip to do with the cable adjustment. It moves the throttle plate directly, ignoring anything the cable or hand throttle control does. (given the screw has been screwed in tighter so that it, repeat IT has opened the throttle plate, NOT the hand throttle and cable control)
If the cable has slack, the throttle plate opening and thus the idle, will be controlled by the screw on the mechanical idle stop, the screw that is on the carb linkage. The cable will only raise the idle IF the cable is shortened and pulls the throttle plate open more than the setting of the idle adjustment screw.
If the idle is too slow, likely the mixture is not set properly. Or there is a mechanical problem with the butterfly or throttle plate.
More likely, the pilot jet is clogged, and limiting the fuel flow at idle and just above. If the engine seems to want to stall, or idles very unstably, the pilot should be a suspect. It may be coincidence or just 'sitting time' with the fuel turning to merde as the BB upgrade took place. Or crud floating around and blocking the jets as the carb it fiddled, dumped, flipped, and set 'wherever' as the upgrade took place. I'd check the pilot jet before doing much more. As you screw the idle setting screw in to open the throttle, the idle should get so high the rear wheel starts to turn as the clutch engages. You should(maybe) be able to see a very small bit of light through the pilot jet when held up to a light source. If not, try running a straight pin through. It SHOULD pass(hopefully w/o doing andy jet enlargement)
tom
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