Carb problem, I think?

[griffbones]

I have a brand new 2007 KX100 and it has a very low idle. If I turn the curb idle screw in it will only raise the idle for a couple seconds and then it falls back down to a very low idle again? If I turn the air screw all of the way in the bike does not die, gets rougher running but doesent die? I swapped out the carb for one off of our KX85, the carb was running great on that engine and it is an identicle PWK 28 carb. I did have to change the main jet and needle to set it up to factory specs for the KX100. But I have the same problem with both carbs and both carbs were set exactly to jetting specs and a air screw setting of 1 3/8 turns out! I tried spraying brake cleaner around the carb, carb boot, reed cage, and cylinder base to check for an air leak and found nothing. What is really strange is that the bike runs perfect other than this idle problem, it even seems to have good throttle response, even coming off of this low idle. I just can't figure why turning the idle screw in won't raise and maintain a good idle and why turning the air screw in won't kill the engine either? I know this second carb is spotless clean and worked great on the 85 just a few days ago, and besides what is the chances of two different carbs, one of which is a known good carb, could both act exactly the same? One carb of course is brand spanking new and as I said the other one is in perfect condition, so is there another mechanical issue that I am missing? Or is it possible that the bike will need a larger pilot jet than what Kawaski and even Team Green recomends? Their correction factor chart shows that the stock 45 pilot jet should still work just fine at the 45 - 50 degrees that I currently have at my location and at my altitude of 800 ft above sea level.
So any ideas guys? I am missing something obvious?
Sorry for the long post.

 

[griffbones]

Any Ideas guys?

 

[IndyMX]

I can't say why you'd see no change, but when you say "low idle", how low? And if it's running good, why worry about idle speed? 2 Stroke engines should not idle for long periods.

 

[2stroke4fun]

I like my bikes to idle low. You have more contol going into corners.

 

[griffbones]

My ten year old son is riding this bike in some pretty tight woods and steep terrain, so he needs a decent idle. This kind of riding is really hard if the bike won't stay running!

I have never had a two stroke that wouldn't die when you turn the air screw all of the way in. And since I could not find an air leak and the plug looks tan, does this mean I need a bigger slow jet?

 

[Bodge]

try putting a leaner pilot jet in it.