YS 91!! Whats the problem??  
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All Forums >> RC Airplanes >> 3D Flying! >> YS 91!! Whats the problem??
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YS 91!! Whats the problem?? - 7/4/2003 10:19:06 AM   
alex24


 

Posts: 367
Joined: 12/9/2002
From: Cockeysville, MD, USA
Status: offline 		I'm having a tremendous problem with my YS 91. I only have about4 flights with this engine and is killing me!
here are my problems or symptoms:
1) At iddle the engine have a change in rpm (about 100 to 200).
in about a minute after it accelerates and desacelrates, the engine suddenly quits. (i changed the spar several times)im usng an OS plug!!!

2) At full throttle the engine is only giving me about7,000 to 7,500 rpm with a APC 13 x 11. (i think this is too little rpms)

3) In one of the flights I inverted the plane and the engine lows in rpms and then quits!!

other considerations: im using Cool Power 15% nitro!
I dont know if this is good, but my high speed neddle valve is about 1 1/16 open... (is that too much closed?, but thats when the rpms are at it highest)

thanks for your answers....
Alex
       Post #: 1

YS 91!! Whats the problem?? - 7/4/2003 11:11:16 AM   
azhar


 

Posts: 571
Joined: 2/21/2002
From: Redmond, WA, USA
Status: offline 		Alex,

Is your engine used in an in-cowl application? If so, it sounds like it may be overheating or it is running a little lean.

I have no experience with the 13x11. I have used 14x8 and 15x6 APC. I run 20/20 fuel and get about the mid to upper 9K rpms. The 15% fuel may cost yoiu some power. Try a 14x8 and see what happens.

Azhar

(in reply to alex24)
       Post #: 2

YS 91!! Whats the problem?? - 7/4/2003 2:26:14 PM   
Nelson Fong


 

Posts: 10
Joined: 3/21/2003
From: Hong Kong
Status: offline 		Alex,

this is a common problem of all YS engine.

I have two YS91AC with the same problem what you had today.
fortunately, all of them are recovered to normal.

First of all, check all screws, the screws are loose when exit factory or after first flight. it cause the pressure inside the engine very unstable. escpecially the valva cover and air chamber. becareful in tighten all screws.

Second, check the codition of the gaskets (valva cover and air chamber), replace it if broken where will cause pressure leak.

Third, screw out the regulator and carefully clean inside. sometime the lubricant oil will stick around there.

Nelson

(in reply to alex24)
       Post #: 3

YS 91!! Whats the problem?? - 7/4/2003 6:25:40 PM   
robert


 

Posts: 2447
Joined: 3/2/2002
From: private, IRELAND
Status: offline 		What type of Os plug are you using, just out of interesT?

(in reply to alex24)
       Post #: 4

YS 91!! Whats the problem?? - 7/4/2003 6:38:15 PM   
alex24


 

Posts: 367
Joined: 12/9/2002
From: Cockeysville, MD, USA
Status: offline 		thanks for your responses! my engine is in cowl! i will cut the cowl a little bit more, because right now the muffler and cylynder head is tight. I will check also al the scews!!!
I will try today again, to see how it works!
By the way how closed you have your high speen needle valva????
Keep flying,
Alex

(in reply to alex24)
       Post #: 5

YS 91!! Whats the problem?? - 7/4/2003 7:33:50 PM   
Sprink



Posts: 2236
Joined: 4/23/2003
From: London, UNITED KINGDOM
Status: offline 		Just in case you don't know, to increase cooling, increase the size of the hole that lets the air OUT, or decrease the size of the air that lets the air IN.

_____________________________

"If it doesn't break, it is probably too heavy"

(in reply to alex24)
       Post #: 6

YS 91!! Whats the problem?? - 7/4/2003 8:14:14 PM   
Nelson Fong


 

Posts: 10
Joined: 3/21/2003
From: Hong Kong
Status: offline 		set the high speed needle 1 1/8 turn.

an OS type F or YS 4 stroke plug must be used.

(in reply to alex24)
       Post #: 7

YS 91!! Whats the problem?? - 7/5/2003 4:27:59 AM   
alex24


 

Posts: 367
Joined: 12/9/2002
From: Cockeysville, MD, USA
Status: offline 		ok i am in the process of making the cowl holes a little bit bigger, that is the hole in the muffler and in the cylynder head!
My high speed neddle is now about 1 1/8 open! i will try tomorrow how it works!!!
Thanks again,
Alex

(in reply to alex24)
       Post #: 8

YS 91!! Whats the problem?? - 7/5/2003 12:49:47 PM   
azhar


 

Posts: 571
Joined: 2/21/2002
From: Redmond, WA, USA
Status: offline 		Alex,

just a note. The needle valve adjustment may vary slightly from engine to engine. The % of nitro will also determine your needle setting. The best way to set it is to use a tach and set it about 100-200 rpm below peak.

Azhar

(in reply to alex24)
       Post #: 9

YS 91!! Whats the problem?? - 7/5/2003 7:13:42 PM   
alex24


 

Posts: 367
Joined: 12/9/2002
From: Cockeysville, MD, USA
Status: offline 		yepa thats right! Im using Cool Power fuel. This fuel have 15% nitro, not 20% YS recommends, but i think it shoukd work.
Hope my engine gets better today!
Keep flying,
Alex

(in reply to alex24)
       Post #: 10

YS 91!! Whats the problem?? - 7/5/2003 9:01:54 PM   
klhoard



Posts: 544
Joined: 9/4/2002
From: Collierville, TN, USA
Status: offline 		Alex,

I have a YS .91FZ on my pattern plane. I've tried the 15% route before, but $adly, you won't get much over 8500 RPM with it (14 x 10 APC). Try a tank of 30% heli fuel and you will have a new engine on your hands. You also have to run an OS-F or the YS 4-stroke plug in this engine.
Remember, this engine has high compression and performance. Also, cooling is a must. Good luck!!


_____________________________

Keith Hoard
Collierville, TN

(in reply to alex24)
       Post #: 11

YS 91!! Whats the problem?? - 7/6/2003 2:15:39 AM   
alex24


 

Posts: 367
Joined: 12/9/2002
From: Cockeysville, MD, USA
Status: offline 		I agree..
I just came from my starting the engine and I think i discover the problem..
I found a lot of bubbles from the small line from the diafraghan to the carburetor.... I think this is a major problem. thats why i have this changes in the rpm in iddle... what do you think guys?? i replace the line to make sure the line wasn't broken...
I think i have to send the engine to YS!!!
Any suggestions
Alex

(in reply to alex24)
       Post #: 12

YS 91!! Whats the problem?? - 7/6/2003 7:15:39 AM   
klhoard



Posts: 544
Joined: 9/4/2002
From: Collierville, TN, USA
Status: offline 		I have bubbles in the line of my YS .91 also. . . . try some 30% heli fuel and an OS-F glow plug. . . .

If that doesn't fix it, send it in. . . .


_____________________________

Keith Hoard
Collierville, TN

(in reply to alex24)
       Post #: 13

YS 91!! Whats the problem?? - 7/6/2003 8:55:48 AM   
azhar


 

Posts: 571
Joined: 2/21/2002
From: Redmond, WA, USA
Status: offline 		Alex,

The bubbles is normal between the regulator and carb. You seem to be having a problem with engine overheat. Open up the cowl some. The YS's do not like to be hot.

Azhar

(in reply to alex24)
       Post #: 14

YS 91!! Whats the problem?? - 7/6/2003 2:03:17 PM   
alex24


 

Posts: 367
Joined: 12/9/2002
From: Cockeysville, MD, USA
Status: offline 		wow bubble are normal in this engine! I though they weren't in any motor!
umm i'm confused now!!I think the bubbles have make my iddle go bad!!! i'm using OS plugs! wow i dont know what to do?

(in reply to alex24)