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HelicopterEngines Plugs Mufflers Fuel › YS91ST Needle Settings?
01-27-2007 08:55 PM  10 years agoPost 1
Dr.Don

rrVeteran

Cedar Park, TX -- USA

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YS91ST with about 2 gallons through it before I got it. Running MPII, 8.27 gears. Having some issues getting the needles set for a good transition from idle through the mid-range. Give me some idea where you guys' needles are. I am in the range in the manual, but not sure which way to go to smooth it out.

Thanks

Dr.Don

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01-28-2007 01:37 AM  10 years agoPost 2
ErichF

rrElite Veteran

Sutton, NH

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Lose the Muscle Pipe, it's inherently unstable with that muffler, for some reason. Get a Hatori or equivalent clone. I got the Century Quiet Tune 90 muffler (made by Hatori), and it's just great. Not as quiet as say a Hatori SB 17 or so, but runs very nice.

I'm on the lean side of the idle needle range, and the rich side of the hover needle, and 3/4 on the high needle.

That's with OS #8, and Cool Power Performance heli 20%, 7.92 ratio, 1900 and 1500 rpm.

Erich

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01-28-2007 04:34 PM  10 years agoPost 3
Dr.Ben

rrMaster

Richmond, VA, USA

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Poor transition can often be caused by either too rich an idle or hover mixture OR a combo of both. If the engine doesn't repond to gently leaning of these mixtures, try another muffler. If the problem persists, replace the carb's barrel. Yes, the barrel. You'll sometimes see one mismachined.

RE the hover needle setting, keep leaning it in until the engine cackles, then richen it back up 4-6 clicks. You must have the midrange tuned correctly or the engine simply won't run worth a darn. Erich is right about the idle mixture. Keep it as lean as reasonable without having the engine hang on the pipe in an auto or other chatter/cackle at idle.

Ben Minor

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01-28-2007 05:18 PM  10 years agoPost 4
jsenicka

rrProfessor

Eagle River, WI

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I am at about 1.25 + a click on hover, and between 5/8 and 3/4 on high speed. Idle is about 1/4 turn in from flush with the housing. Still a bit rich. Agree on needing to get the midrange right!

Jim Senicka
Team Manager, GrandRC Flight Team

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01-30-2007 05:27 PM  10 years agoPost 5
Dr.Don

rrVeteran

Cedar Park, TX -- USA

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Thanks for the help guys. I am going to invest some more time fiddling before I give up on the MPII. Will concentrate on getting the hover needle right, then move back and tweak the idle needle. No time to get on it until the weekend...too dark when I get home now.

Dr.Don

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02-03-2007 01:57 PM  10 years agoPost 6
jsenicka

rrProfessor

Eagle River, WI

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I would look at an MP5 if you want to stay with the MP.
YS on a Hatori is a thing of beauty. YS on an MP2 will always be tweaky

Jim Senicka
Team Manager, GrandRC Flight Team

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HelicopterEngines Plugs Mufflers Fuel › YS91ST Needle Settings?
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