New build motor, 91 or 105?

[ktmdiesel]

Since the os 91 is out of production does that mean the parts are going to become rare/more expensive. I plan on building a new trex700 in the spring. There are some cheap new 91s kicking around, but I don't really want to cheap out either. Am I better off just spending a couple hundred more and getting the 105 hz? Better yet the hz-r (not exactly sure how much the regulator helps )
What decent priced but good exhaust are you guys using? I've heard the mark up is terrible just for having certain names on it.

Thanks in advanced and sorry to plug up the forum. I just want to do this right the first time.

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[ktmdiesel]

Also any word on a new kit coming out anytime soon? It would be so dissapointing picking up the dfc if a new one came out a month later

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[narcisstking]

Give the YS Tareq 91SRX a glance. Can easily find matching Hatori (soft mount) pipes for these. Easy to tune and find parts for. Monster power too. Have one installed in my N7.

[smwht]

I run the 105 hzr in all my 700s. I've tried the YS 91/96 but they just haven't worked for me. I use the powerboost pipe currently. I'd recommend the hzr over the Hz. The regulator makes it more consistent.

You can get a better price at rcjapan, but you lose the us-based warranty. I'm not sure how much that covers anyways, I've never actually tried to warranty one of my engines.

If you're just getting started in nitro, there's something to be said for learning how to tune with a cheap engine so you're out less when you blow it up. Then upgrade when you start hitting the limits of the engine.

Sorry that's not really an answer either way it kind of comes down to what you're looking for. The 105 will have a lot more power, but costs more and is a bit harder to tune than the os 91.

[jiminator]

I agree with smwht. When learning nitro it would be better to learn on something cheap. Don't think any big block motors were around when this video was shot, don't know if its a YS or an OS, but Bert seems to be doing just fine whatever it is.

Bert Kammerer TREX 700 Blacksheep 2008 (7 min 48 sec)

Synergy is coming out with a new pipe for the 1.05.

[ktmdiesel]

Going with a smaller engine.. safe then sorry lol

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[Thestructured]

Originally Posted by jiminator

I agree with smwht. When learning nitro it would be better to learn on something cheap. Don't think any big block motors were around when this video was shot, don't know if its a YS or an OS, but Bert seems to be doing just fine whatever it is.

Bert Kammerer TREX 700 Blacksheep 2008 - YouTube

Synergy is coming out with a new pipe for the 1.05.

That video is with an Align 91H

it did just fine on the old gear ratio

[907Heli]

I went with the 105 because parts are still easy to find, the ys91 is notoriously hard to tune, and i got a deal on a used one. I was going to buy new and couldn't decide between the ys 96 and os105, either way I'll only have a regulated engine.

[narcisstking]

I rebuilt a SRX last year and the total price was about $90.00 which was for a piston, ring, liner kit and two c-clips for the wrist pin. Pretty bloody cheap. Put about 3.5 gallons through it since then with naught an issue.

[jsbach#1]

Just a positive plug for the YS96 today. A friend maidened his 650 goblin nitro with it. We followed the basic instructions of no governor enabled 50 percent throttle opening maximum and followed the recommendations for the needles. OS 8 plug, cool power 30 percent.

I can not fault it at all. It started up just fine, idled just fine (definitely a little on the fat side) it hovered just fine, for a few tanks, then it flew around smooth upright gentle circuits at 60 percent opening nice and fat, never a hiccup.

Can't commend on behavior when you start to tune for a bit of power and enable governor cause haven't got there yet. But so far ran like a clock, almost confused at the less than OS reliable reputation YS has unless the 96 SRX is a major departure from motors of past from them.

[Baedarlboo]

Yeah I don't know if people really tried their hands on YS motor or they're just regurgitating stuff. I've got a YS96srx, 91srx, and a 91sr and they all run like clock work. They all are consistent, and make loads of power. The one time I did actually burn up a motor was because I got mixed up on needles. YS and OS run opposite needles of each other...I was coming from a OS91 and tuning a YS for power after break in. Other than that, they like the mid range a little fatter than OS. I wouldn't say they're more temperamental than any other nitro motor.

[DCflyer]

Originally Posted by Baedarlboo

Yeah I don't know if people really tried their hands on YS motor or they're just regurgitating stuff. I've got a YS96srx, 91srx, and a 91sr and they all run like clock work. They all are consistent, and make loads of power. The one time I did actually burn up a motor was because I got mixed up on needles. YS and OS run opposite needles of each other...I was coming from a OS91 and tuning a YS for power after break in. Other than that, they like the mid range a little fatter than OS. I wouldn't say they're more temperamental than any other nitro motor.

+1

This whole notion of "YS motors are hard to tune" is a thing of the past at this point. That may have been true for YS motors a few iterations ago, but not so much today. My YS120 was no harder to break in and tune than my OS55. Fired right up. Idle screw needed to be rotated 30min richer, but that was it. Rock solid after that. The new "X" generations of YS motors (96srx, 120srx, etc) are even better with revised crankshafts for less vibrations, better cooling, and revised needles for a wider tuning window.

Regulated motors do have a bit more involved though so a lot of the bad stories you hear are definitely going to be user error. Regulators can clog. Check valves can fail. It takes a little time to learn it all.

[jsbach#1]

You know what I saw on the morgan fuel website, an Omega badge of heli fuel with 1% castor oil content of its total oil content.

Anybody use this ? I just prefer the smell thats all

[Skeezix]

Originally Posted by DCflyer

+1

This whole notion of "YS motors are hard to tune" is a thing of the past at this point. That may have been true for YS motors a few iterations ago, but not so much today. My YS120 was no harder to break in and tune than my OS55. Fired right up. Idle screw needed to be rotated 30min richer, but that was it. Rock solid after that. The new "X" generations of YS motors (96srx, 120srx, etc) are even better with revised crankshafts for less vibrations, better cooling, and revised needles for a wider tuning window.

Regulated motors do have a bit more involved though so a lot of the bad stories you hear are definitely going to be user error. Regulators can clog. Check valves can fail. It takes a little time to learn it all.

Thought I'd add to an old thread for future users....
I'd be interested as to when you think the YS motors became easier to tune? I got my first nitro heli about a year ago, and used a YS 91ST. I rebuilt the engine and it idled fine, but just wouldn't run consistently and kept dying. Nothing kills the fun of a nitro heli like an unreliable engine. After several weeks (and many lost hours of flying) and help from several different club members, I gave up and bought an OS 105HZR. I've had exactly zero problems with the OS since day one.
Maybe I'm just unlucky and understandably, the 91ST is an older engine, but I found the OS to be rock solid....and the OS 105 will run on 15% nitro, which is an added bonus!

[HelisRock]

Originally Posted by jsbach#1

You know what I saw on the morgan fuel website, an Omega badge of heli fuel with 1% castor oil content of its total oil content.

Anybody use this ? I just prefer the smell thats all

Great memories, nothing like the smell of castor oil and the sound of an expansion chamber! Would it give the same smell with nitro?