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Polini Thor 200 rough running at 5000rpm


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I have a Polini Thor 2oo Evo engine. With a Bing carburettor fitted. The engine has always had a little problem, engine runs fine from tick over all the way up to 4900 rpm and from 6100 and higher. However the engine runs rough between these two power settings. If I make the smallest throttle movement the revs will run rough and if I keep making small increases in power I get to a point where the power band kick in and it jumps up to 6000 rpm and runs sweet as a nut. unfortunately for me at 6100rpm The aircraft wants to climb and I can’t maintain a level flight and 4900 the aircraft will descend. Any suggestions would be much appreciated

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Suggest decarbonisation of everything, exhaust, exhaust ports, piston, cylinder head, etc.

That seems to be the most common issue wirh 2 strokes, assuming that ignition and carburation have been checked.

Carbonisation usually leads to atarting problems too as well asrough running in a specific rev range.

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  • 4 months later...
  • 8 months later...
On 21/04/2018 at 11:12, WIlly said:

Thought I’d reply to this problem I had.

we figured out what was wrong. And it was so simple, closed the mixture screw in and opened it up 1 and half turns. The power cure is perfect now. Happy flying 

Hi @WIlly

Could you please explain a bit more of this solution? I am having the same prob with my moster 185+.



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