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Niggly engine issue


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Ok so i've got a small engine running issue i'm trying to figure out all though this might just be a normal thing with two strokes.

The engine revs drop when I open the throttle lots quickly, if that makes any sense. It idles fine, and if you open up the throttle at a reasonable rate it delivers fine. It is probably a good thing that the revs drop a bit as its a Bailey JPX 330 and would probably start swinging me back and forward in no time at all if I were to open up throttle at that speed, however it would be nice to know that power would be there instantly if I needed it.

I started by checking the fuel line. The inline filter was a bit crappy so that's been changed out. There were a few bubbles in the air line but not a massive amount, probably just vapourisation. The carb filter has been checked, no issues. As most people I haven't used the motor for a few months so used some carb cleaner which made the engine sound a bit smoother but still didn't eliminate the main issue. I've tried doing it when the engine has warmed up and the rev drop isn't as severe but you can still hear it drop.

Any ideas folks?

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At this point I would like to hand over to someone with knowledge of that carb :-)

But I am fairly sure (with the oil on the props) that this may be the solve to your problem.

I am not familiar with that carb enough to advise but I am sure someone will jump in and save me :-)

SW :D

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If it makes a hollow sound when you open the throttle quickly, that's classic lean behaviour. If it runs rough (fires every other cycle) it's too rich.

Try richening your carb settings and see if it gets any better. No one ever blew a motor from it being too rich...

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If it makes a hollow sound when you open the throttle quickly, that's classic lean behaviour. If it runs rough (fires every other cycle) it's too rich.

Try richening your carb settings and see if it gets any better. No one ever blew a motor from it being too rich...

I agree with the above diagnosis.

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Most two strokes...

Open the throttle fast and a lot of air is drawn into the carb/cylinders.

This leads to a lean condition as the main jet hasn't got out of bed yet.

So manufacturers place an additional slow running jet on the carb that

introduces fuel quickly for this event.

Its got a blockage or not opened enough.

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Think its solved now, had a flight the other day and gave it plenty of time to warm up before launch by holding the throttle at 50%. Didn't have any problem after a couple of minutes of that. Throttle opened up fine with instant power. Probably a jingle bell stuck in there from crimbo ;)

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