I'm not for sure but I believe the cause would be a bad plug or a overly rich setting.
Have you checked your plug? your plug may be a defect or just plain worn out.
When plugs get worn out some just can't keep up the heat required the make the next round of fuel ignite without the assistance of a glow plug igniter.
And if your overly rich there is to much fuel for the plug to ignite and the fuel 'extinguishes' the glow plug.
And sometimes plug just well.. suck and need to be replaced right of the pack.
And lastly have you broken in your engine yet?
Wait for the help of others because I *think* this is whats wrong..
The plug you use depends on the nitro content and what yourmotor calls for. The higher the nitro content the cooler plug you can use. You really can't go much wrong with a plug like an OS #8. Not too hot or too cold. Good in the middle plug. :microwave That is what I use on 20% and 30% fuels. I know some will scold me for that but the way I see it...if it runs good use it. So I would get me a couple new plugs and try them out. See what your engine likes best.[/SIZE]