help me with carb screw settings

[xsk3l3t0rx]

so i took out the aftermarket air fiiter. and put in the a fresh element. connected the hose, clamp, and closed the airbox, it accelerates much better now, and the speed is better too. i ride an 87 spree, so what i did was screw the air screw in all the way til it was just a little snug. then i backed it out like 1 whole turn then a little more (i think its supposed to be 1 3/8 turns), then i turned the idle one until the back wheel started spinning, once i found that point, i backed off a little on the idle screw til it stopped, is that what you guys mean when you say finding the optimal idle speed before the "clutch" kicks in? is this thing good to ride now? i think i did everything right, but i dont want the engine to seize or anything cuz im a total noob wit automotive stuff, thanks all!

[Kenny_McCormic]

At least you are aware of what seizure is. Air screw should be out 1.5 turns, the idle stop should be set with the bike hot, slow it down till the back wheel can easily be held with your pinky finger.

[Clivester]

The spec air mixture screw settings are set up to be optimal for a new factory-fresh carb. With wear or dirty jets that may no longer be the case. Rather than just set it to spec its a good idea to determine the optimal setting for your carb. If it turns out you determine it to be way off from the spec setting, it means you still have carb issues such as a partially blocked idle jet.

Here is a procedure you can use.

Make sure the scooter is fully warmed up.

Start with the air mixture screw at the recommended setting for your model. I like to use a sharpie marker to put a reference point on the screw. Rotate the mixture screw slowly in or out 1/4 or 1/2 turn at a time and wait to see if the rpm changes. A tachometer helps greatly here but is not necessary. Notice where it starts to stumble when screwing it in and also out. Those two points are usually a turn or so apart, but may vary a lot. About 1/2 way is in the ball park. Set it for maximum rpm and then go in about another 1/8th to 1/4 turn. That last 1/4 turn makes it slightly richer, but any rpm decrease should be nonexistent or small.

You may find that your mixture adjustments will increase the rpm a lot. Then adjust the idle screw out a bit to a lower rpm. You want the rpm low enough that the back wheel does not spin. Adjusting it at a low rpm is more sensitive and accurate.

With it idling as best as it can be, run the idle speed screw up about 1/2 turn at a time. Each 1/2 turn should produce an increase in rpm of about an equal amount. If there is no change, it starts stumbling, or it runs slower you have other carb issues you need to check. The two most common reasons are plugged idle gas jet and/or an intake leak.

Clive

[scooternewby]

Now THAT was some good advice! I hope this does not get deleted because I need to do exactly that tomorrow!