WIlly Posted December 4, 2017 Share Posted December 4, 2017 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 Quote Link to comment Share on other sites More sharing options...
Dave Stuart Walsh Posted December 6, 2017 Share Posted December 6, 2017 Could there be any carbon build up in the exhaust. This sounds like a problem I had with an outboard years ago. Took off the powerhead and the exhaust size was reduced by 50% by carbon. Did exactly what you describe. Reason was previous owner running on cheap oil. Quote Link to comment Share on other sites More sharing options...
cianpars Posted December 6, 2017 Share Posted December 6, 2017 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. Quote Link to comment Share on other sites More sharing options...
WIlly Posted December 6, 2017 Author Share Posted December 6, 2017 Thank you I’ll take the exhaust apart to try the decarb. Will post back soon Quote Link to comment Share on other sites More sharing options...
GR002 Posted December 7, 2017 Share Posted December 7, 2017 Was there not a reed valve up grade on the Polini 200 due to non linear power band? This was a couple of years ago and I do not know how old your engine is ,might not be this but thought I would mention it. Quote Link to comment Share on other sites More sharing options...
WIlly Posted April 21, 2018 Author Share Posted April 21, 2018 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 Quote Link to comment Share on other sites More sharing options...
Jo-bkfire Posted December 31, 2018 Share Posted December 31, 2018 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+. Thanks! Joe Quote Link to comment Share on other sites More sharing options...
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