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HelicopterEngines Plugs Mufflers Fuel › any Reports on YS 91 SR?
08-11-2007 03:35 AM  10 years agoPost 1
azfaith

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Las Vegas

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So who has one? Any user reports yet? I am getting ready to buy a 90 size engine for a Freya EVO90.

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08-11-2007 08:16 AM  10 years agoPost 2
tadawson

rrElite Veteran

Lewisville, TX

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Just finishing an X-Spec with a 90SR in it now . . . hopefully, I'll get it in the air in a week or two. If it performs like my other YS motors (50 and 80), it's gonna be sweet . . . . The good news is that, unlike the 80, the 90 has the same exact shaft size as the OS90, so it was a perfect fit in the Freya (the 80 needed some extra parts due to the 8mm shaft . . . ).

- Tim

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08-11-2007 11:31 AM  10 years agoPost 3
MrMel

rrProfessor

Gotland

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My friend has run it in his stratus for a month, and I just put in one replacing a OS91SZ/OMI/Viperhead in my Stratus, ive completed the run-in.

Torque! alot of it!
And its running AMAZINGLY smooth!

Only thing I wonder is if the old Viperhead for the YS91ST fits (have it at home, havent tried it yet), since that could probably make it run even smoother (now if that is possible)

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08-11-2007 12:57 PM  10 years agoPost 4
Tyler

rrElite Veteran

Chicagoland area

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YS 91 SR

OMI told me not to use the existing YS viperhead, but rather wait for the new SR viperhead. He said it will be worth the wait because there are significant changes needed for the new head. Can the existing one be made to work? Yes, with some care to a few details, but it won't work as well as it does on the ST engines.

Initial thoughts on my two YS 91 SR's: Loads of torque, user friendly needles, consistent runs. One has a MP5 and the other an SB-19 and both engines seem promising. I am finishing up the run in process and chasing a few helicopter mechanical issues that prevent me from really flying the SR's to their potential. Hope to have this all up and running perfectly this weekend.

Tyler

Enjoy things that money can buy IF you don't lose the things money can't buy.

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08-18-2007 05:41 AM  10 years agoPost 5
derekandjennys

rrApprentice

Cedar Rapids, IA

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Ditto
But have not tried the 19 yet. Are you narrowing on a muffler yet. I have broken 4 MP headers in the last few weeks. 2 on the new SR with new MP5. During smooth break in flight. But don't want to break a $180 muffler either.
I belive the problem has something to do with a reverberation like the limiter kicking on and off and sometime just before during or after I have a broken header. It just hit me that I started breaking them after switching to MP5 and limiter from MP2 and TJ Pro. For the short while the C Spec Big Bore, Kline, Viper was insanely awesome. I have a hard time thinking the SR could compete, but new Viper and broke in we'll see.

When is the new Viper available? Wasn't the St viper black and there is now a red one for the SR?

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08-19-2007 10:34 PM  10 years agoPost 6
CBell

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Nova Scotia, Canada

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I had the chance to fly three different YS.91 SR's at IRCHA, and all of them really impressed me. I plan to replace my two OS.91 SZ's with the YS SR's. The .91 SR is smooth, extremely consistent, easy to tune and makes awesome power.

Colin

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08-20-2007 07:16 AM  10 years agoPost 7
derekandjennys

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Cedar Rapids, IA

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Did they all have the same pipes?

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08-20-2007 07:18 AM  10 years agoPost 8
derekandjennys

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Cedar Rapids, IA

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Also, did you take note of the gearing? I have a feeling that the 8.18 I am running is going to prove to be about the best.

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08-20-2007 12:43 PM  10 years agoPost 9
Chuckie

rrKey Veteran

Crofton Maryland

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I've been running my N9s with SRs for the last few months and can report it is a great motor. It has more power and torque than the tried and true ST4 and it's just as easy to tune. I'm using the SB-19 and this exhaust gives the SR way more torque than the 16 or 18. I have not tried the MP5 but from what I've seen the motor runs equally as strong. I do think the SR sounds better on the 19 when tuned for max power.

The N9 uses 8.27 ratio and I've tried 1700, 1800, 1850, 1900, and 1950 rpms. The motor pulls hard regardless of the headspeed so the limiting factor in climbout out and roll rate is the headspeed selected. I'm using +-14 pitch and I'm sure the motor could handle more. However, at 1950 the motor is running too fast. I suggest 15,300 to 15,700 is a good motor rpm to run. Flight times are shorter on the SR as you don't get power for free. Running the motor at 15,300 will help with fuel burn as well as running less pitch.

Cheers

Charles

Please stand by for faster service!

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08-21-2007 05:00 AM  10 years agoPost 10
CBell

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Nova Scotia, Canada

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All machines had MP5's on them. Two of them had an 8.27:1 ratio, and the other was at 8.45. I'm going to try 8.27 and 7.92 once I get the motors. I'll let you know what I think of both ratios. I'm currently running my OS's at 8.27.

Colin

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08-21-2007 08:00 AM  10 years agoPost 11
derekandjennys

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Cedar Rapids, IA

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8.45 should be too high for the SR. I had to start playing with throttle setup a little as the limiter needed to be turned off for break in and tuning, and I lowered the bottom of the V as it was overspeeding slightly and slowing it down at 8.18 it was even stronger.

I really think that 8.18 will prove to about the best. I leaned it out a little more trying to tune it. It is starting to feel pretty good but I have worked up to loading it more. Having a little trouble tuning this thing. The low is easy but I keep leaning the mid. The manual said 1.75-1.5 and I was at 1.25 so I richened in back to 1.5 and it sounded leaner. But didn't feel any different. Although I am only on the third gallon and the first 2 were Sig 15 for breakin so I am not really pounding on it.

You said easy to tune but I have alot of years on the OS and it just seems alot different.

Derek

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08-21-2007 11:47 AM  10 years agoPost 12
Chuckie

rrKey Veteran

Crofton Maryland

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You said easy to tune but I have alot of years on the OS and it just seems alot different.
I would agree Derek. I never owned an OS and don't have a clue to how to tune one for running the best. These motors are different and so is the tuning. 1.5 is a good place for the mid during break in. The mid is the primary fuel valve so if you lean it out after break in the high and maybe low need to be adjusted. On OS the high is the primary fuel valve.

Where you set the needles depends upon outside temps, exhaust, fuel etc. I adjust the motor based on how it sounds, smoke output, and temp after flying maneuvers like stationary tick tocks, loops, rainbows, and full speed climbouts. The easy to tune part about the YS is the needles, once set, don't need adjusting during the day or over a short period of time. This is mostly true if you run the motor on the rich side. I usually have to adjust the motor as the season changes to keep it from running hot or burning extra fuel.

Colin, let us know what you think of the SR on the Hatori SB-19 exhaust. I've been trying to test fly my machine/motor with the MP5 but haven't been able to 'borrow' anyone’s exhaust.

Charles

Please stand by for faster service!

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08-21-2007 10:27 PM  10 years agoPost 13
derekandjennys

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Cedar Rapids, IA

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I think Collin is Sponsored by Curtis.

Does anyone have a 2 plug Viperhead yet?

Charles
I know what you mean, I do have an St4 on my night fly / backup machine but have only flown it a couple times a year. It has been in there for 3 or 4 years and I may change the high a click or 2 when I do fly it. I think if the needles were moved I would have a hard time finding it again. It is not ideal as it is at 7.91 So you leave the high rich and adjust the mid for power during harsh midrange flight such as tic tocs? I know I am close but part of it is I am rushing to get it ready for the Ringout in MN this weekend and don't feel it is ready to really load it. I believe I am at just over 14 degrees also, 8.18 and i am guessing 1850. Can't turn on the governor just yet and only one guy at our field has a tach.

Has either of you flown a C-spec, Big Bore, Cline, Viper, MP5 for comparison?

Colin
Just watched your 07 XFC flight, good stuff, I was curious how much pitch you were pulling. I like your skid slide. I use to touch the skid alot when I was running 10-10 but for the last year at around 14, it is a little too jumpy for me to risk it. Or am I just being a wuss?

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08-21-2007 10:41 PM  10 years agoPost 14
hansking12

rrApprentice

irvine, ca

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my sr motors have been running flawlessly

i must echo chuckies comments on the smoothness and power of this motor with the sb19 pipe. it is just like my other ys's in that it needs minimal fiddling with the needles and generates gobs of power and torque. in fact, it's making me lazy with the inputs because the thing just pulls through 'loady' type of flying. i have found that it doesn't like super high rpm and is more of a torque monster. i wouldn't run it past 15k, 15,200 max rpm though, it just doesn't need to rev so high to produce big power.

the head is different, so i wouldn't try using the old viper head on the sr motor.

i have not had a chance to run the mp pipe on the motor, however one of our group has run the motor on the sb16 and although it sounds smooth and quiet, the power is not at the same level as with the sb19. ymmv

in short, awesome motor. and i have cspec omi modded and sz omi modded motors for comparison. . .for some reason, the ys runs much cleaner, not as much residue and doesn't require the same fiddling with the needles.

regards,

hans

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08-21-2007 10:53 PM  10 years agoPost 15
CBell

rrApprentice

Nova Scotia, Canada

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derekandjennys,

Thanks for the kind words. I'm running about 14-15 degrees of pitch. If you find it a little jumpy you can try to flatten your pitch curve slightly around center, that will help smoothen it out. Like you've mentioned, I am exclusively flying Curtis' gear.

Colin

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08-21-2007 11:14 PM  10 years agoPost 16
P.J.

rrVeteran

Ireland

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My YS 91SR was flying great until today, Its only on Its 3rd gallon and bang

P.J.

SAB Heli Division
Hyperion
Spektrum RC
Scorpion Systems
Spartan rc

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08-21-2007 11:58 PM  10 years agoPost 17
airdodger

rrElite Veteran

Johnston USA

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I see the problem right away, it has an air leak in the crankcase.

Chris

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08-22-2007 12:09 AM  10 years agoPost 18
derekandjennys

rrApprentice

Cedar Rapids, IA

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UH OH, I am still on the 3rd gallon! WHAT DID YOU DO!?!?

Not the old Viper I was pretty sure the new red single plug Viper was available. Is it for the SR and where is the dual glow plug version. I have been unable to get ahold of James, he called back once or twice, but still have not connected.

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08-22-2007 12:14 AM  10 years agoPost 19
cdrking

rrElite Veteran

Seattle

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WOW, I've never seen a YS engine do that.

PJ,

What RPM were you running the engine at? Also what combo were you running?

Jeff

To hover is divine, the alternative is rather PLANE.

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08-22-2007 12:18 AM  10 years agoPost 20
P.J.

rrVeteran

Ireland

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cdrking,

I was running 1840 rpm on an MP5

P.J.

SAB Heli Division
Hyperion
Spektrum RC
Scorpion Systems
Spartan rc

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HelicopterEngines Plugs Mufflers Fuel › any Reports on YS 91 SR?
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