Have you finished breaking in the motor? If not you need to finish the break in procedure. The engines manual can be downloaded from CEN's website.
If you have finished breaking in the motor reset the carb to factory specs and change the glow plug then start tuning like the manual say's. Remember tune the HSN first then tune the LSN.
Here is an article that might help http://wildhobbies.com/news/default....&articleid=959 I am sure that there are other similar articles but this is the first on that I remembered.
There is also a possibility that you have an airleak somewhere. To correct this you will need to tear the motor apart and re-seal it.


rolland