Originally Posted by mp43sniper
Jetting is tuning the air fuel mixture by changing the slow and main jets and the needle position in the carburetor. Any time a change is made that can affect jetting (different air filter, different exhaust, elevation change, etc) you should "re-jet" the carb.
On a two stroke street bike, they tell you to run wide open at top speed and then at the very same instant pull in the clutch and hit the kill switch. You coast to a stop and pull the spark plug and see what it looks like (called "reading the plug"). If it's black you're too rich (jet too big or needle clip too high), brown it's close or ok, and white or gray it's too lean (jet too small or needle clip too low). You do NOT want to be too lean or the engine can be damaged or seize up. Too rich will just waste oil and make everything all gooey in the exhaust. My engine isn't here yet so I don't know how many adjustments are possible with the common chinese two stroke bicycle engine most of us are using. The needle may not be adjustable. Heck, there may not even be any aftermarket jets either. There is a possibility that all the adjustments are made with the mixture screw, I'm just not sure.
I agree with the statements that you should be able to run an engine 24/7. However with an air cooled engine, remember they should be moving for proper temperature regulation. So as long as you're riding, not idling, keep on truckin.
oops you got it backwards on the needle clips, lowering the clip raises the needle and richens the mixture. Vice versa
On my first build, it was WAY rich and 4 cycling at highest clip positon.
I soldered up the main jet and drilled it out in steps with torch cleaning bits from NAPA. Started with .018, but the next size, .023" was perfect ,after moving the clip around some.