What I usually do when aquiring a tired old 2-stroke motor is:

Strip the carby.

Soak it in petrol.

Make sure you clean the little mesh filter - Top right in this pic > [link=http://www.polini.com/dep/928_440_008_maxi.jpg]CLICK[/link]

Clean the high/low needles.

Reassemble carby.

Make sure all the bolts for the cylinder head are eaqually tightened.

If the carby has a primer bulb make sure it's not cracked or has a leak.

Check the fuel lines and breather cap on the fuel tank.

Play around with the high/low needles.

I usually start with them both turned out about 1 1/2 to 1 1/4 turns and go from there.