Back Pressure Problem Raptor 90

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Old 07-23-2012, 05:52 AM
  #1
gjgibson
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Default Back Pressure Problem Raptor 90

Raptor 90 starting problem. Recently put together the helicopter. When sarting the bird it won't start until you hold your finger over the end of the exhaust pipe to sart the fuel flow to the engine.
The engine starts fine but then dies as soon as you take your finger of the end of the exhause pipe.
The engine runs fine as long as you hold your finger on the end of the muffler, but as soon as you take your finger of the engine dies.
The problem seems to be that there isn't. enough back pressure to keep the fuel running to the engine when the exhaust pipe is not resricted.
The fuel tank and the header tank are both full of fuel and there does'nt seem to be an air lock in the fuel line.
Any advice as to what the problem and a resolve would be greatly appreciated.

Regards
Grant Gibson
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Old 07-23-2012, 05:54 AM
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BarracudaHockey
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Default RE: Back Pressure Problem Raptor 90

Is your needle open far enough?

The engine should draw enough fuel to run at idle even without exhuaust pressure
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Old 07-23-2012, 06:17 AM
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gjgibson
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Default RE: Back Pressure Problem Raptor 90

Hi Andy thanks for getting back to me so quickly.

I've tried adjusting the "Needle Valve" on the left hand side of the engine ( which controls the mixture strength of the engine speed range from half to fully opened throttle ) with no affect.
I haven't tried adjusting the "Mixture Metering Screw" which controls the mixture strength of the speed range from idling to half opened trottle.

I would think the adjustment should be the latter but correct me if I'm wrong.
Not sure as to what to focus on first !
Any suggestion.

Cheers
Grant
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Old 07-23-2012, 09:14 AM
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Default RE: Back Pressure Problem Raptor 90

What kind of engine do you have?

Is your throttle open enough to make it run and not in the 'kill' zone?

Perhaps try and go back to the factory settings for the needles. If it doesn't run after you make it richer, then there must be a blockage in your carb or lines somewhere.
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Old 07-25-2012, 10:54 PM
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Default RE: Back Pressure Problem Raptor 90

I had a similar problem with the ****ty tt39 and it ended up being the glow plug... I understand a 90 and 30 are worlds apart but thats a simple thing to check. id also check the fuel lines to ensure there is no stopages. remove any inline filters to rule them out.
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