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Home✈️Aircraft🚁HelicopterAlignT-REX 700N › OS 91 HZ Shim or not to Shim
02-22-2010 05:23 PM  10 years ago
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NQNA

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USA

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OS 91 HZ Shim or not to Shim
About ready to install my OS 91 HZ. It ships with an extra head shim. Are you guys running the extra shim? And do you know the +- of it?

Thanks
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02-22-2010 05:49 PM  10 years ago
Kevin Dalrymple

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Indianapolis

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At the height above see level we are you will need to run 2 thick shims in the summer time. you can get away with a think and a thin right now at this cold temp.

I am running the 2 thick shims. I beleive they are .004 = thin and .008 for the thick. i am running .016 head spacing now in my HZ.
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02-22-2010 10:16 PM  10 years ago
jsenicka

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Eagle River, WI

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depends on your fuel!
15%? No.
20%? doubtful
30%? depends on oil package.
On CY30 I find I needed to shim
Jim Senicka
Team Manager, GrandRC Flight Team
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02-22-2010 11:57 PM  10 years ago
NQNA

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USA

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I'm looking at running CY 30% and generally fly the nitro's in 65 degree to 95 degree temps. Sounds like I'll be putting in a shim.

.016 the correct amount?
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02-23-2010 12:55 AM  10 years ago
NQNA

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USA

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Looking online at O.S. they show an extra 0.2mm head gasket as being included...
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02-24-2010 01:11 AM  10 years ago
jsenicka

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Eagle River, WI

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that gives you .016 in inches (original .008 and one extra).
At sea level in warmer temps I needed .020 on my HZ engines with CY30 to get decent needle range. Same engine at 1600 feet (my Dad's place in Wisconsin) I only needed .016.

If you are near sea level in Ohio, I would go for .020 (two thick and one thin) if you want to run CY30
Jim Senicka
Team Manager, GrandRC Flight Team
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02-24-2010 02:06 AM  10 years ago
NQNA

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USA

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We run around 800 to 900 msl in Beautiful Ohio!
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02-24-2010 03:06 AM  10 years ago
jsenicka

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Eagle River, WI

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you could likely get by with .016.
Symptom of too much compression (need more shim) is only a few clicks between snotty rich and crackly lean
Jim Senicka
Team Manager, GrandRC Flight Team
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02-25-2010 02:05 AM  10 years ago
S.Dykes

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Wesley Chapel, FL - USA

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.12 to .16 will probably do good in your region of the country. But if you bring your heli to tampa you will need to stack up the shims, from .20 to .24.
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03-01-2010 03:04 AM  10 years ago
ualdrivr

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Long Island, NY

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Page 16 of your manual explains everything you need to know about the head gasket/shim. I added the extra one to the one already thereAt the precipice, we change!
Team GrandRC
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03-02-2010 03:30 AM  10 years ago
NQNA

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USA

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I'm planning on putting the extra shim in the engine.

Thanks All.
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03-05-2010 01:55 AM  10 years ago
THX1138

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Indianapolis, IN

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What about Magnum fuel? Should I run the extra shim?

Lou
Just give me five dudes and two flashbangs...
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03-05-2010 03:27 AM  10 years ago
THX1138

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Indianapolis, IN

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Well, I read through the engine manual a little better and did a little more on-line research. I think that adding the extra shim is the smart thing to do if you are going to run 30% fuel so I went ahead and installed it.

I am taking the day off tomorrow and weather is supposed to be really nice so I am going to try to maiden my 700 and start breaking in the engine. Word.

Lou
Just give me five dudes and two flashbangs...
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03-05-2010 03:45 AM  10 years ago
outhouse

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auburn ca

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I have a fresh case of %30 rapicon and ive installed 3 shims, 2 thick and the thin and hopefully ill get a few tanks through and report back tomorrow.
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03-05-2010 04:27 AM  10 years ago
LonR

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Macomb,Mi

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NQNA,im in the next state over.In my OS 91 im running Wildcat 30% performance with 2 .008 shims (.016) and the motor runs awesome with tons of power.600LE,OS55,OS PowerBoost pipe,Align 610's,Spartan
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03-05-2010 07:03 PM  10 years ago
outhouse

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auburn ca

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flew one tank %30 rapicon and the 3 shims, so far tuning is easy and a big increase in power [less bogging] over the %20CP.

im getting close on the tuning and allthough not dialed down to the click,,,, me likey
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03-06-2010 11:05 AM  10 years ago
Popcorn

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Switzerland

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30% Rapicon and not any shims works perfect for me. tons of power and easy to tune...
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03-06-2010 12:48 PM  10 years ago
THX1138

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Indianapolis, IN

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I put the first two tanks on mine yesterday. So far the engine runs like a clock. I am still on the factory settings of 2 turns out on each needle, but I the engine does not miss at all. I think the extra shim is for sure the way to go. I'll get one more flight on her and start leaning the engine a little bit at a time over the next gallon. Very smooth and no vibes at all. I am very stoked about this engine!

Lou
Just give me five dudes and two flashbangs...
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03-06-2010 12:49 PM  10 years ago
THX1138

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Indianapolis, IN

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Oh yeah, 30 Magnum heli plus, MP6, and OS #8 glow plug. Word.

Lou
Just give me five dudes and two flashbangs...
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03-07-2010 02:43 PM  10 years ago
devious17

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Malaysia

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According to the manual. 30% add extra shim, 15% not required. I run CP30% withthe shim added and with good performance.
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