RE: jett fire 50 on d dust
I'm referring to the intake port in the crank.
The hole creates an unbalance in the crank, which is not insignificant at high rpm levels... If you have got a counterbalanced spinner backplate, then the heavy side of the backplate should be on the same side as the intake port in the crank. This will, for a part, take care of the unbalance. All front intake FAI racing engines use counterbalanced spinners too, for this reason.
Hard to make out from the pic if it is actually counterbalanced.
My Jett counterbalanced spinner backplate has a piece of steel (or some other metal) glued into a machined slot at the rear side of the backplate.
I see no reason why you couldn't run heli fuel... but Jett recommends Powermaster, which has a 1/3 castor-2/3 synthetic oil package.
I use Rossi 8 or Nova Rossi 9 plugs on high rpm engines... they seem to last longer. These are very cold plugs. I haven't noticed any detrimental effects on idle when using 15% nitro.
The [link=http://www.jettengineering.com/]Jett website[/link] has excellent instructions on it... read them... You will find them under "Tech specs and Instructions"