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HomeRC & PowerAircraftHelicopterEngines Plugs Mufflers Fuel › Low end needle closed?
06-26-2015 11:39 AM  3 years agoPost 1
SkateFreak

rrElite Veteran

Cambs UK

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Long story short I am running some home brew fuel through an OS70 in a t-rex 700.
(20% Methyl Easters/80% methanol) + Prosynth 5% nitro fuel (50-50 mix).

The carb got blocked recently and the engine was running erratically so stripped, cleaned and rebuilt the carb following an exploded diagram.

Back to factory settings (hi-2/mid-1/low-centre) and started working on getting the needles set.

From factory settings start with the low end adjustment.
Idle was horrendously rich and the engine was running stone cold, moved the low end leaner until it reached its maximum setting of 90 degrees. Still a bit rich on idle though?

Working through the other needles, high end needle ending up just over one turn out and mid around half a turn but the low/mid range is still overly rich and the high end is very sensitive (rich -> lean in a few clicks).

Is there a chance I have re-assembled the carb incorrectly which could cause these symptoms?

Could it be the low nitro (2.5%) is having an effect and +/- a shim would help the engine run better?

Any thoughts would be much appreciated.

Best regards

-Jvr

Non-3D heli pilots are planker spys trying to bring down the heli community from the inside - Topher

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06-27-2015 12:26 AM  3 years agoPost 2
EEngineer

rrProfessor

TX

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Is there a chance I have re-assembled the carb incorrectly which could cause these symptoms?
I would re-check the carb re-assembly, first.

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06-27-2015 05:25 AM  3 years agoPost 3
PilotPin

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Indiana -- USA

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How much run time does your engine have.
(rich -> lean in a few clicks)
is a sign that the ring and sleeve are worn out.

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06-29-2015 12:18 AM  3 years agoPost 4
SkateFreak

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Cambs UK

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The engine is pretty fresh (gallon at most) and all looks happy with the head off/through the exhaust port.
As I was spending much time diddling the needles I didn't get to run through a whole tank in one go but I did notice it was going through the engine at quiet a rate!
Will get the carb apart again but not sure what I could have gotten wrong as I followed the exploded manual closely and it's pretty straight forward unless I missed something unintuitive during disassembly 8-/

Beat regards

-jvr

Non-3D heli pilots are planker spys trying to bring down the heli community from the inside - Topher

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06-29-2015 04:24 AM  3 years agoPost 5
PilotPin

rrApprentice

Indiana -- USA

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The carb got blocked recently
Could you explain this in more detail?

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06-29-2015 07:38 AM  3 years agoPost 6
SkateFreak

rrElite Veteran

Cambs UK

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I suspect I put the fuel filter on backwards which flushed some small particles into the carb.
The engine was behaving erratically going lean and then richening up again and on disassembly I found the carb was fouled with lite grains in the needles :-|
Disassembled to clean out and reassembled via exploded diagram and memory. Now the low end needle is fully turned in (90 degrees), the idle is still on the rich side and top end is rather sensitive.

One thing worth noting is the seals have swollen slightly due to some of the oil in the fuel.

Best regards

-jvr

Non-3D heli pilots are planker spys trying to bring down the heli community from the inside - Topher

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