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HomeRC & PowerAircraftHelicopterEngines Plugs Mufflers Fuel › O.S. .91HZ tuning: loosing revolutions while looping; why?
03-15-2010 12:57 AM  8 years agoPost 1
sumonzu

rrApprentice

San José - Costa Rica

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Hi there,

I'm having a problem with my new O.S.91HZ not pumped.

My setup is main needle 1 TURN + 6 clicks and middle needle 1 turn + 6 clics (the same as the main one). I have a Stratus, the engine sound very good either at maximun and any speed, but when doing looping - more exactly when at the top, half loop - it looses a lot of revolutions (sometimes even it seems about to "die" and I have to considerably reduce the pitch/throttle to recover the regular revolutions.

NOTE that I'm using the Futaba governor GV-1 and it worked fine with the old engine (an OS 91 too).

I suspect that when looping the governor sense that the engine become to loose revolutions and automatically opens the carb trying to give more fuel. NOW I do not know if the engine is too rich or too lean. So what to do? Open o Close more the middle needle in order to have smooth and consistent transitions?

Any suggestion will be very appreciated.

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03-15-2010 01:03 AM  8 years agoPost 2
outhouse

rrVeteran

auburn ca

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you need to know if its rich or lean first.

make sure its not getting to hot.

I wouold pop the gov and eliminate that first but i suspect tuning.

Hows compression? taken a look at your piston and ring lately?

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03-15-2010 04:57 AM  8 years agoPost 3
sumonzu

rrApprentice

San José - Costa Rica

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That's the problem: I do not know if it's rich or lean, however the engine is not too hot while running.

Also the heli climbs well at full throttle so I do not suspect any compression problem; I have to say that once it run for a while (just 3-5 minutes quite hot because it was running lean).

Piston were ok and ring... must be how if it is fine?

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03-15-2010 06:00 AM  8 years agoPost 4
outhouse

rrVeteran

auburn ca

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then possible its to rich.

use allot of caution going lean or you will toast it. dont let it get to hot. [either use a temp sensor or finger on backplate for 8 seconds or so]

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03-15-2010 06:03 AM  8 years agoPost 5
Duckster

rrApprentice

Brunei

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try open ur mid neddle, i find that hz non pump are good at 1.5 less 3 click on top and mid at 1.5 if it getting worst try to lean it back, its is better try on rich side rather then lean, but sound like ur mid is lean,and how much is ur cyclic and pitch r u using, if it is more and poor collective will make this thing happpen just IMHO

Trex 600,700 AND 450, GY611, GY401, OS5H, OS91HZ, MGP, HS65HB, Scorpion 2221-8,

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03-15-2010 04:36 PM  8 years agoPost 6
arfwrecker

rrNovice

modesto cal u.s.

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mixture
get a good laser temp gauge. fly the machine doing some hard load heavy load maneuvers land quickly and thke a temp at the head. YOu would like to see 180deg to 210, 210 being lean like max power. at 180 your engine will last a long time at 210 you wel acchieve max power but your engine will need ring liner poston lots sooner. I fly my 90 sz os at 180 and i run 180 and it gets reasonable fuel economy(economy funny word with 90) and good power for my sport flying. Good luck make sure it is a good temp gauge, I use a stanly purchased at sears and it has been good for me.

arf

90/3d raptor sz all quick uk upgrades cy muscle pipe.

electrons , auto when you want to not have to, love the clean up. Heliproz team pilot

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03-22-2010 06:18 AM  8 years agoPost 7
sumonzu

rrApprentice

San José - Costa Rica

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Thank you to all over there.

Soon I'll try all the suggested options: I'll let you know!

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03-22-2010 10:31 AM  8 years agoPost 8
saigon-heli

rrApprentice

Ho Chi Minh

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Hi all,

Does anyone know how does the mid range valve work? It's easy to visualize how the idle and high valve works but I still do not understand how the middle valve control the fuel flow to engine.

Thanks,

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03-23-2010 06:09 AM  8 years agoPost 9
arfwrecker

rrNovice

modesto cal u.s.

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mid valve
the mid valve does just what it says it is to fine tune the low end transition, meaning most of the single needle carbs of yesteryear would either load a little at just off idle i.e. mid or low end, but would have good peformance at high needle to balance it out they added the low/or mid needle to aid and stop flameout after like a long time idle, after the transition to high idle the top end or high end needle takes over and the low end is shut so for temp at the top on performance you adjust rich or lean to balance temp and power to lean high temp for a short while, lower temp taken at top of cyl head by the glow plug after some bruising load is 180 deg, F High temp and risk is like 210 deg f. which will give you great power but take its toll on your motor.

electrons , auto when you want to not have to, love the clean up. Heliproz team pilot

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03-23-2010 06:20 AM  8 years agoPost 10
sumonzu

rrApprentice

San José - Costa Rica

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mid valve
the mid valve does just what it says it is to fine tune the low end transition, meaning most of the single needle carbs of yesteryear would either load a little at just off idle i.e. mid or low end, but would have good peformance at high needle to balance it out they added the low/or mid needle to aid and stop flameout after like a long time idle, after the transition to high idle the top end or high end needle takes over and the low end is shut so for temp at the top on performance you adjust rich or lean to balance temp and power to lean high temp for a short while, lower temp taken at top of cyl head by the glow plug after some bruising load is 180 deg, F High temp and risk is like 210 deg f. which will give you great power but take its toll on your motor.
Wow that's hard to understand that... or not?

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