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HelicopterEngines Plugs Mufflers Fuel › OS 91HZ-R 3D Speed engine
06-08-2012 12:18 AM  5 years agoPost 1
dchekas

rrKey Veteran

Farmington, CT

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I've had some trouble from this engine since I purchased it.

It replaced a 91HZ-R engine in my T-Rex 700N. I am using a Funtech B301 pipe and Byrons RotorRage 30% masters blend.

I cannot make this motor run slobbering rich. With the main needle at 3 1/4 turns out, and the mid range at 1 1/4 out, not only was I able to smoothly spool up, take off, and fly around, but the helicopter would perform continuous tic tocs and other 3D maneuvers effortlessly.

Changing the main needle from 2 turns to 3 1/4 turns out has virtually no effect on the engine. The mid range needle also doesn't appear to have any significant impact on flying.

Leaning the high speed needle below 2 turns causes the engine to run rich, but any kind of loading, even gentle tic tocs, makes the motor lean out excessively.

I've replaced the entire fuel system, including the fuel tank, fuel filter, all fuel lines, and fuel magnet. The exhaust is sealed.

The thing is, I'm 99% sure the issue lies in the carburetor. As a test, I installed a friends 61ER carb (The one that came with the original 91HZ-R), and the motor runs great! Needle settings are right in the ball park with everyone elses.

At this point, I've also tried swapping out the regulator and main needle with a working 91HZ-R regulator and main needle. Made no difference.

I'm really leaning towards a defect in the machining of one of the fuel paths in the carburetor. I can't fathom what else could be causing the issue at this point.

It seems to me to lie within the carburetor, and it's not the regulator or a damaged main needle.

Anyone have any suggestions? I'm completely stumped at this point.

The carburetor has been returned to hobby services, where they reported that there was "debris inside the regulator". Unfortunately, when I got the carburetor back and tested it yesterday and today, it made no difference.

Team Align, Team Futaba, Team Byron Fuels, Team Thunder Power

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06-08-2012 01:02 AM  5 years agoPost 2
BladeStrikes

rrElite Veteran

Shelby TWP,Mi

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I also had the OS 91HZ-R and that motor ran awesome and easy to tune.Was thinking about the OS 91HZ-R Speed after switching to the YS 91SR 3DS just so I can see which makes more power..After replys about the carb,I stuck with what I have..Seems ALOT of people have issues with the Speed carb and end up sticking the standard OS 91HZ-R carb on it because it runs perfect as you already found out...Ive seen way more bad about the Speed carb than good..
If it was my motor (I know you don't wanna hear this),I would stick the standard OS 91HZ-R carb on before trashing the motor.The last thing you want is to trash the ring or whole motor,pick up a used OS 91HZ-R carb and keep sending the Speed carb in until you get a good one..

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06-08-2012 04:47 AM  5 years agoPost 3
ahensley323

rrNovice

Savannah, GA

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I have (had) the same situation with my Speed motor. I could not go to 2 turns before it would start to lean out on hard flying. The main needle is around 3 turns out and mid between 1 1/4 and 1/1/2, makes great power on those settings. Anything less and it starts to lean. I just flew it like that, has many good flights on it. I replaced it with the 105, but will keep the speed as backup because it screams. Bad batch of carbs???

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06-09-2012 05:24 PM  5 years agoPost 4
dchekas

rrKey Veteran

Farmington, CT

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It's my guess that something went TU on a batch of these carbs, I wish I knew someone local I could swap carbs with, but most people around here are still running the 91HZ-R.

There's many posts on here and the other site reaffirming that the needle settings are in the ball park of the 91HZ-R on a properly running 3D speed engine.

Having flown the 61ER carb and then this one back to back, I will say this: That carb is what makes the engine come alive. With the 91HZ-R carb, you basically get 91HZ-R performance. The speed carb makes the engine a MONSTER.

Team Align, Team Futaba, Team Byron Fuels, Team Thunder Power

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HelicopterEngines Plugs Mufflers Fuel › OS 91HZ-R 3D Speed engine
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