Possibly more likely to be carb / fuel related, but if you have spare ancillaries, swap each one - one at a time until you find which is at fault, and / or borrow ancillaries for one session to find the fault, there is usually someone in the paddock who'll lend you an item just to 'eliminate it from your enquiries'.
Do you have the carb slide restrictor in the carb top, if not the Mini may bog due to air speed slow down through the carb when the throttle is opened too much. The restrictor should avoid this. Even with carb restrictor in driver needs to be progressive with throttle opening - don't snap the throttle open as most do coming from cadets!!!!!!!
try smaller main jet, unlikely to be this though.
needle valve in carb may need replacing - it's not sealing properly when the floats act on it causing a high fuel level in the carb and a rich mixture which maybe clears a bit when the revs pick up. You'll need a ground down socket (or small ring spanner - grind down the outside of it) to get the jet out- replace the body and needle as a pair, don't forget to pluck out the little fibre washer at the base of the jet body - you should get a new one with the needle jet kit. A good indicator that the needle jet is not sealing is fuel flows back when you blow it into the carb sucking aif into the pipe from the carb. Don't worry if this happens on first couple of blows from carb being stood for a while - needle jet rubber tipped end needs wetting with fuel to seal.
Get floats are right way up and the little pegs are acting on the float leaver from BOTH floats, if not could give rich mixture.
Check there is no hole in the floats (we had one once with a hole)
For mini clip 1 or 2 from the top is usually the richest you want to go.
Is your needle straight, roll it on glass to check.
Bit more involved but accelerator holes between the venturi insert and the carb body could be blocked, ultrasonically clean carb, put new rubber gasket and make sure holes in gasket do not mask holes in carb body. Put venturi insert in freezer and carb body in oven - no more than 100C to help drop in and line up - you only got a second or two before temp equalizes.
Slim chance could be fuel pump needs rekit, but unlikely if high revs OK
7000 to 9000 is when engine is under a fair bit of load and also when ign system is under load and will breakdown if it's going to - more so plug, plug cap, lead, less so coil.
Slim chance exhaust could cause a problem, re pack etc check baffle, but unlikely.
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Rotax spluttering 7000 to 9000 revs by '1509' (26 Jan 2015 @ 7:58)
