I have a new webra heli engine SPEED 75. runs good when started. The problem is when I try to start it , it pops the prop nut loose. (I have it on a break in stand wit pressureised fuel tank.
I hope someone can help.

Kick back is usually caused by to lean of a needle valve setting. Try richening up the high speed needle valve. It ought to be around one and half to two turns out. Other causes of lean runs are air leaks, so check out all the possible leak areas like the back plate and carb throat sealing.

Good luck,

Chip

As Chip says and add that too much nitro will cause it also, more than 5% in a Webra is too much.

Thanks Guys for your feed back. Sorry for the delay but went on vacation (in west texas of all places).
set to a little richer and double nuted the prop and used lock tight, seemed to have worked. now all i need is to run a gallon or so fuel through it.
thanks for your help

Riversam

Hi!
Probably too lean ...or too much nitro. Do not use anymore than 5% nitro.