[SLESTAK75]

The main jet only affects the acceleration at wide open throttle. If you are experiencing this problem at takeoff it is NOT the main jet. Either there is a slight air leak somewhere, a bit of trash in the carb somewhere, the pilot needs adjusted, or the needle and jet in the second stage needs adjusted. Even improper float level can affect the carb working right. One hard jolt such as landing from a jump or something similar can get the float valve out of adjustment and even a 1-2mm difference in this setting can have an adverse affect on the carb. try removing and cleaning the carb. remove the pilot screw ( noting first how many turns out from completely seated it is ) and blow out inside of there. Here is a link to a good description of tuning these carbs.

http://www.factorypro.com/tech/tech_...m_engines.html

http://www.google.com/url?sa=t&rct=j...,d.dmg&cad=rja