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siavreg · 10-07-2008, 03:14 PM

Pretty much as the title says. The only thing is that i would like to use the muffler i have now. My engine now is a YS91ST and to be honest I'm not happy with it. The head keeps coming loose and when I removed the head last time i checked the piston and there is a chunk missing from the outer edge above the sleeve.
Time for a change.
Fire away with suggestion
siavreg

Badger50 · 10-07-2008, 09:23 PM

Hey Siavreg: Well here is my 2 cents worth, and that's about all its worth LOL.
Over the past year, I have had both combinations on my Rap-903D.
1) The YS 91SR with Hatori 19b pipe was an easy tuning powerhouse, once I got the hang of the needles. I can say the same for the OS 91SZ-H non-pumped engine with the Hatori 18b pipe.
2) They both run great with CYB 30% with both head shims in them.
3) I liked the pressurized system with the YS, provided the check valve is working good, I like the simplicity of the OS, running with muffler pressure, but you've got to get the mid-range needle correct, which I didn't at first, and it cost me a piston, sleeve, and con-rod replacement. However now she runs just great after the rebuild.
4) I think the YS performs better at lower RPM's, but I like the way the OS runs at higher RPM's which is good for 3D aeorobatics.
5) The OS balances my heli out better, but at the cost of extra weight, however, I run the Kasama head, so the difference wasn't that noticable to me.
6) I have found getting parts to be pretty equal between the 2, with a slight edge going to the OS.
7) If you search the forums real good, you will see an equal opinion on both engines, however most of the ones I've read, give the power edge to the YS engine. Since I have only been flying for 2 years, I am not as attuned to engine performance as many others on here, but in my opinion, they are pretty close in comparrison.
8) Now that you have my 2 cents worth, you probably think....I still don't know what to buy LOL. But believe me when I say this, they are both very good choices, and will work just fine, provided they are setup, and maintained properly. I hope I was able to help you out, but I probably didn't

Oh well, thats the beauty of this hobby, there is no right or wrong, there is only....What can I afford

I wish you luck with your choice.

siavreg · 10-07-2008, 09:43 PM

No thats great info.
I'm not really to sure on which way i want to go so this info is very helpful. I've only ever had a good with OS engines before in both my raptor 30's. Kind of like set and forget. With this YS there always seem to be something. I don't want to give up on the YS line I just want to here thoughts and opinions just like yours on why each one is good.
I did do some searching on here about the engines and came up with nothing really good on why people use them or why they don't.
One more Question... where is a good place to get a new piston and ring for my YS 91ST?

Thanks again

Badger50 · 10-08-2008, 03:20 PM

You might try these guys, looks like they have a prettty good selection of parts.

http://www.world-of-heli.de/en/motor...rts/index.html Or if you want to use someone in the states, these guys are very good, http://www.ronlund.com/Merchant2/mer...gory_Code=YS91

Lota Fun R · 10-09-2008, 04:28 AM

I just switched from a SX91 C spec pump to a SZ91 non pump.

The SX could put out the power needed ( ran 2180 wide open). The SZ does too, the SZ is supposed to have a little more power and I'm sure it does. I'm still tuning mine.

I think my mid is too lean?

Carb smart goes rich pretty fast and the main is open enough.

10-07-2008, 03:14 PM	#1 (permalink)
siavreg Registered Users Join Date: Apr 2006	I want to buy a new motor for my 91SE, suggestions and why? Pretty much as the title says. The only thing is that i would like to use the muffler i have now. My engine now is a YS91ST and to be honest I'm not happy with it. The head keeps coming loose and when I removed the head last time i checked the piston and there is a chunk missing from the outer edge above the sleeve. Time for a change. Fire away with suggestion siavreg __________________ Trex 600E, 2 -Trex 450, Mcpx BL, Turnigy FBL 100, Assault 700

10-07-2008, 09:23 PM	#2 (permalink)
Badger50 Registered Users My HF Map location Join Date: Oct 2007	Hey Siavreg: Well here is my 2 cents worth, and that's about all its worth LOL. Over the past year, I have had both combinations on my Rap-903D. 1) The YS 91SR with Hatori 19b pipe was an easy tuning powerhouse, once I got the hang of the needles. I can say the same for the OS 91SZ-H non-pumped engine with the Hatori 18b pipe. 2) They both run great with CYB 30% with both head shims in them. 3) I liked the pressurized system with the YS, provided the check valve is working good, I like the simplicity of the OS, running with muffler pressure, but you've got to get the mid-range needle correct, which I didn't at first, and it cost me a piston, sleeve, and con-rod replacement. However now she runs just great after the rebuild. 4) I think the YS performs better at lower RPM's, but I like the way the OS runs at higher RPM's which is good for 3D aeorobatics. 5) The OS balances my heli out better, but at the cost of extra weight, however, I run the Kasama head, so the difference wasn't that noticable to me. 6) I have found getting parts to be pretty equal between the 2, with a slight edge going to the OS. 7) If you search the forums real good, you will see an equal opinion on both engines, however most of the ones I've read, give the power edge to the YS engine. Since I have only been flying for 2 years, I am not as attuned to engine performance as many others on here, but in my opinion, they are pretty close in comparrison. 8) Now that you have my 2 cents worth, you probably think....I still don't know what to buy LOL. But believe me when I say this, they are both very good choices, and will work just fine, provided they are setup, and maintained properly. I hope I was able to help you out, but I probably didn't Oh well, thats the beauty of this hobby, there is no right or wrong, there is only....What can I afford I wish you luck with your choice. __________________ Mike: Rap-90 3D x 2, Rap-50 x 2, Fury 55, Rex-450, Hirobo Squark. *"Depression is nothing more than anger, without enthusiasm"*

10-07-2008, 09:43 PM	#3 (permalink)
siavreg Registered Users Thread Starter Join Date: Apr 2006	No thats great info. I'm not really to sure on which way i want to go so this info is very helpful. I've only ever had a good with OS engines before in both my raptor 30's. Kind of like set and forget. With this YS there always seem to be something. I don't want to give up on the YS line I just want to here thoughts and opinions just like yours on why each one is good. I did do some searching on here about the engines and came up with nothing really good on why people use them or why they don't. One more Question... where is a good place to get a new piston and ring for my YS 91ST? Thanks again __________________ Trex 600E, 2 -Trex 450, Mcpx BL, Turnigy FBL 100, Assault 700

10-08-2008, 03:20 PM	#4 (permalink)
Badger50 Registered Users My HF Map location Join Date: Oct 2007	You might try these guys, looks like they have a prettty good selection of parts. http://www.world-of-heli.de/en/motor...rts/index.html Or if you want to use someone in the states, these guys are very good, http://www.ronlund.com/Merchant2/mer...gory_Code=YS91 __________________ Mike: Rap-90 3D x 2, Rap-50 x 2, Fury 55, Rex-450, Hirobo Squark. *"Depression is nothing more than anger, without enthusiasm"*

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10-09-2008, 04:28 AM	#5 (permalink)
Lota Fun R Registered Users Join Date: Aug 2007	I just switched from a SX91 C spec pump to a SZ91 non pump. The SX could put out the power needed ( ran 2180 wide open). The SZ does too, the SZ is supposed to have a little more power and I'm sure it does. I'm still tuning mine. I think my mid is too lean? Carb smart goes rich pretty fast and the main is open enough.

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