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HelicopterMain Discussion › 90 size motors- YS & OS which models?
07-13-2008 01:06 AM  9 years agoPost 1
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rrApprentice

Maine

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Good evening,

I'm looking into .90 size motors. I don't have any experience with them- both YS & OS engines seem to each have various model designations, which I don't understand. Would someone give me the quick run down on current model .90 designations on these two engines? Also do some come with pumps as an integrated unit or are pumps add-ons - are they necessary? I'm not looking for an OS v. YS thread just an understanding of each model so I can understand the classified ads.

Thanks a lot.

Christian.

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07-13-2008 01:49 AM  9 years agoPost 2
airboss

rrElite Veteran

OC ,california

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these 2 engines are both of good quality and either will suit your needs. currently I am using the YSsr(long stroke) in my synergy's. my previous engines were both versions of the OS , szh hyper pumped and szh non pumped.both perform the same and are easy to adjust. if you are shopping for a 90 and you want to set it and forget it, then get the OS szh non pump.but if your looking for a bit more mid range power then get the YS sr. prices are equal but mufflers are a bit less costly for the OS.

Urukay HPS3 KSE 700 HPS3

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07-13-2008 01:57 AM  9 years agoPost 3
baby_zyklon

rrElite Veteran

Singapore

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YS
Both the 91ST and newer 91SR are not exactly pumped, but regulated. Meaning it uses crank pressure instead of muffler pressure and fuel goes through the regulator before going into the carb. The 91sr is more powerful(supposedly more powerful than the OS), the 91ST has needs more revs to work.

OS
There are a few variants of the 91sx-h, from the very basic and plain 91sx-h to the pumped c-spec with viper head. The newer ones are 91sz-h, available with or w/o the pump. The latest is the 91HZ, which is not available yet, unless you go for the align version. OS also has got RX-H and RZ-H, these are rear exhaust, the S series are side exhuast. A pump is suppose to make the engine run consistently from the a full to empty tank, however from what has been discussed, the non-pump version is the way to go.

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07-13-2008 07:39 PM  9 years agoPost 4
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rrApprentice

Maine

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Thank you Airboss and Baby Zyklon for your replies and help.

Christian

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07-14-2008 11:14 PM  9 years agoPost 5
MANCHA

rrVeteran

Cabo San Lucas,​Baja- Mexico

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I use both ( YS & OS ), I like both.

OS has problems with ball bearings specially in the 50 sector , YS has not.

I buy OS when I can not find a YS.

MANCHA

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07-15-2008 12:09 AM  9 years agoPost 6
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rrApprentice

Maine

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Hi Mancha,

Thanks for the reply. It looks like I may have found a YS. Thanks for the information.

Christian.

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07-15-2008 12:24 AM  9 years agoPost 7
JAGNZ

rrProfessor

Auckland, New​Zealand

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The new OS HZ is supposed to one nice piece of kit and perhaps the first OS 91 that is very smooth and easy to tune out of the box. OS's, even up to the SZ-H (pumped and non-pumped) can be a bit trickier than the YS's to tune but up until the new YS SR most agree the OS's were ahead in the power stakes game.

So, to recap, the new YS (SR) is meant to make great power and the new OS91 HZ is supposed to have some of the good traits which only YS has had previously. YS's require more plumbing due to their crank pressurised system and most pilots universally agree that Pumped OS engines (without mods) are rubbish due to crappy pumps.

Plus, the benefit of the HZ is that Align is rebranding them now and as a result you can bet they will be cheaper to buy.

BTW - the latest Align HZ Motor and new 91 Pipe info is here:
http://www.runryder.com/helicopter/t444649p1/

HTH


Jason Greenwood

www.3dheli.co.nz

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07-15-2008 12:32 AM  9 years agoPost 8
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rrApprentice

Maine

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Hi Jason,

Thanks for the information- I've read exactly what you've written regarding the OS/pump. I trust that the YS if it comes thru for me will suit my needs just fine. Power isn't my big need at this time- nor the near future I'm sure. I'll look forward to it. I'll keep my eyes/ears open on the new OS and see how that turns out. Might be what I replace my used one with some day. Thanks for the pipe link.

Thanks again.

Christian.

PS- regarding the engines and pumps- is the "Perry" pump I've seen here on RR an after market item that can be used in lieu of others?

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07-15-2008 12:40 AM  9 years agoPost 9
JAGNZ

rrProfessor

Auckland, New​Zealand

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AFAIK, some of the older OS Engines shipped with the Perry Pump (Ex. C-Spec) and most considered it complete crap.


Jason Greenwood

www.3dheli.co.nz

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07-15-2008 01:04 AM  9 years agoPost 10
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rrApprentice

Maine

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Thanks again Jason for the reply/information

Christian.

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07-15-2008 01:06 AM  9 years agoPost 11
JAGNZ

rrProfessor

Auckland, New​Zealand

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Happy to help.


Jason Greenwood

www.3dheli.co.nz

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