carb adjustment

[gwcrim]

Some background info: I'm pretty good with carbs. I have an '89 KX500 with a 170 main and 60 slow jets. I live in the upper Ohio River Valley, elevation 1000', temps 35-55* and I've been using MX2T @ 40:1.

When I bought the bike it wouldn't idle. Easy fix: adjust the idle speed screw. That worked but it was nearly all the way in. So I adjusted the idle mixture screw from 2 turns out to 1.5. That really didn't effect the idle much. Not as much as it should have IMO.

Most carbs I've messed with leave quite a few threads showing. Maybe it's just the colder/leaner air, but I thought I'd ask:
Is it common for the idle speed screw be nearly all the way in?

 

[Chief]

gwcrim,

Just a few thoughts. The colder temps should be making your bike idle higher if anything. If you've exhausted all other adjustments, check for wear on the idle screw, also a leaner pilot jet would give you a higher idle. My recommend Airscrew setting is from .5 to 2 turns out. It is a fine tuner for the pilot jet and kinda subtle. I use it to get rid of the lean surge when it starts to get colder out. Once I'm turned in to .5, I go to a bigger pilot jet. With a little experimentation you should get the results you want.

Joe Chief