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HomeAircraftHelicopterEngines Plugs Mufflers Fuel › Shim tha HEAD?
01-18-2010 12:06 PM  8 years agoPost 1
RAVVEN

rrNovice

Rustenburg, South Africa

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would it be nessesary to shim the head of a OS50 if I go from 15% nitro to 30%?

ABC- Always Be Controling!!

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01-18-2010 12:14 PM  8 years agoPost 2
Aaron29

rrProfessor

USA

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nope

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01-18-2010 01:29 PM  8 years agoPost 3
FlaG8r

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Florida

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you will most likely have to change the mixture though.

Life is tough, it's tougher if you're stupid

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01-18-2010 02:36 PM  8 years agoPost 4
30636086

rrKey Veteran

Tacoma, WA

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The safest thing to do is to rich your mix a bit and then start to lean it as need it always keeping an eye in the temperature.

I dont suffer from mental iIlness, I actually enjoy mine!

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01-18-2010 07:39 PM  8 years agoPost 5
jschenck

rrProfessor

La Vista, NE.

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open up the idle mixture along with the main needle. If your engine is tuned to the 15% pretty well you'll want to start off with your main needle at least 1/2 a turn open from the current position.

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01-19-2010 12:30 AM  8 years agoPost 6
Raptor Pilot

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Northern Ireland U.K

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I used to run 10% in my O.S but when i went to CP 30% i had to open the main at least half a turn and richen a wee bit at idle. Never had to touch the head with a shim at all. Runs great on the 30%.

If it doesnt move and its meant too... use WD 40. If it moves and its not meant too...use duct tape!

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01-19-2010 01:06 AM  8 years agoPost 7
Yug

rrMaster

UK. Herts

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Like most has said, shimming the head is usually not required, but if you do need to retard the ignition due to higher than normal ATP, then a shim can be beneficial in the same way it would be in a quick burn viper-head.

Vegetable rights and Peace

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01-19-2010 02:27 AM  8 years agoPost 8
jsenicka

rrProfessor

Eagle River, WI

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I have run the 50sxh on 15, 20 and 30% at sea level, from 30 to 100f air temps.
Needed some mixture changes, but never a hint of over compressed detonation.
Definate needed on 91 motors but not the 50.

Jim Senicka
Team Manager, GrandRC Flight Team

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01-19-2010 03:26 AM  8 years agoPost 9
w8qz

rrVeteran

Grand Rapids, MI - USA

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Most OS engines seem to work well with the higher nitro % fuels. It's the European engines that are designed for lower nitro - like a Webra, for instance, that you'd want to shim to lower the compression ratio when run on higher % nitro fuel.

"The helicopter is much easier to design than the aeroplane, but is worthless when done."

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01-19-2010 07:26 AM  8 years agoPost 10
Aaron29

rrProfessor

USA

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I hear guys with the OS91 shim the head for higher nitro, but the Hyper 50 pretty much loves higher nitro without changes.

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01-19-2010 07:18 PM  8 years agoPost 11
Raptor Pilot

rrVeteran

Northern Ireland U.K

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Thats true for the webra, they are designed to run on no or very low nitro fuel. I never had a webra in a heli but i have them in planes and they are a very powerful engine on 5% nitro.

If it doesnt move and its meant too... use WD 40. If it moves and its not meant too...use duct tape!

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