need to fly my Fox, but

Everything looks good right through run up, then when I'm all lined up on the runway and add full power the power comes up then drops off, rpm just drops 600 or so If I power back it's fine then power up it drops.
I bought the electronic balancing tool and it balances fine.
this is a standard Rotax 912 with bing and all.

any suggestions? Also dose any know of any good Rotax Mechanics in Washington state?