Wrong idle gap and consequently improper needle settings. Set idle gap to 0.5-0.7mm, both needles flush with their housings and re-tune from there. Get it to idle reliably without quitting by keeping glow plug heated and lean the low speed needle until it will idle. Then set the high speed and go back to the low side to get a clean transition from idle to WOT. The engine should run 240-270F when tuned properly using a MEDIUM heat plug and 20-25% nitro. DONT use a hot glow plug!! Adjust the needles in SMALL increments.