YS 91 Exhaust Problem  
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YS 91 Exhaust Problem - 6/17/2002 11:28:38 PM   
jnjones


 

Posts: 2
Joined: 7/7/2002
From: Magnolia, TX, USA
Status: offline 		I have a YS91 AC mounted in my Aeroworks Edge 540 60/90 and I can't seem to keep a muffler on it. After several flights every muffler I've put on it has come loose. The second muffler I tried ( a stock YS 120) actually "split" at a weld seam. On the third muffler ( a stock 91FZ muffler) that I tried the tail piece came off during flight. I even used high temp. red silicone sealant on the bolts that attach the tail piece to the rest of the muffler. "Performance Specialties" suggested that the exhaust is over-heating and that probably need to get more air flow to the motor. I have an area of nearly 3" x 4" already cut out of the bottom of the cowl with the stock holes in the front. Has anyone else experienced these sort of problems, an if so what was the cure?
       Post #: 1

MUFFLER - 6/18/2002 4:44:44 AM   
BUDMAN



Posts: 41
Joined: 2/2/2002
From: PEORIA, AZ, USA
Status: offline 		GET A AAP MUFFLER FROM CENTRAL HOBBIES. THAT WILL CURE YOUR PROBLEMS.............
[url]WWW.CENTRALHOBBIES.COM[/url]

(in reply to jnjones)
       Post #: 2

YS 91 Exhaust Problem - 6/18/2002 6:39:10 AM   
Crash_N_Burn



Posts: 535
Joined: 3/29/2002
From: d, AL,
Status: offline 		I heard the same things about the YS muffler problem, so I just omitted it....easier to cut the cowel, too....




This is a YS 91FZ also...just used a flexible Hobbico exhaust deflector instead of the muffler.

Sounds GREAT, not that much louder and the cowel is easier to remove, too.

No worries about buying new mufflers anymore.....


_____________________________

-dave-

(in reply to jnjones)
       Post #: 3

YS 91 Exhaust Problem - 6/19/2002 5:13:02 AM   
jnjones


 

Posts: 2
Joined: 7/7/2002
From: Magnolia, TX, USA
Status: offline 		Thanks for the comments and the pictures. I've ordered the tail piece of the stock muffler that vibrated off from YS Engines. I'm also going to fabricate a straight pipe in conjunction with threaded header that is still on the engine. Also, I believe that the prop that I was using (APC 15 x 6) might be the wrong prop for this engine, allowing it to rev too high (i.e. 9,500 rpm). I'm going to give a 14x10 APC prop a try.

(in reply to jnjones)
       Post #: 4

YS 91 Exhaust Problem - 6/19/2002 5:34:59 AM   
Crash_N_Burn



Posts: 535
Joined: 3/29/2002
From: d, AL,
Status: offline 		For my situation, a 14-6 works well. Had lotsa problems with being unable to land properly with a 15-10 and a 15-8, 15-6 and a 14-8, went to the 14-6 and real slow on landing....Revs a little high 9,600 but I always run at 1/2 throttle......

.......your situation may differ.

Good luck with the muffler problem...you can always wire the parts on so you don't lose them.....


_____________________________

-dave-

(in reply to jnjones)
       Post #: 5

Join the club - 6/19/2002 7:16:46 AM   
elmshoot


 

Posts: 568
Joined: 12/27/2001
From: Nashville, IN,
Status: offline 		Jones,
I have the same set up w an YS .91AC I had heard all the stories about the muffler. So I safety wired the top of the muffler to the plane. I blew the lower part off the muffler. I replaced just the lower part with anothe muffler from a NIB YS .91 I put a piece of safety wire on what I thought was the correct part of the lower part of the muffler were the threaded part was. I did it wrong and during the next session I blew the lower part off again.
I called performance RC and talked to them about my problem they have discontinued the muffler I have and want 49$ for the replacement muffler. He did have a used one they finally sent me a great price. I installed it correctly and during my last session the whole muffler came loose.
My solution will be to remove the muffler, clean all the threads with acetone then install with RED Loctie or what ever the auto shop recomends for the application then resafetywire the thing and a helo guy says that a tailboom clamp from a helo may fit and will help to hold the SOB in place.
I feel your pain!
Sparky

(in reply to jnjones)
       Post #: 6

YS 91 Exhaust Problem - 6/19/2002 8:48:28 AM   
mrbonk



Posts: 600
Joined: 2/18/2002
From: BundabergQueensland, AUSTRALIA
Status: offline 		[QUOTE]Originally posted by Crash_N_Burn
I heard the same things about the YS muffler problem, so I just omitted it....easier to cut the cowel, too....

Sounds GREAT, not that much louder and the cowel is easier to remove, too.

No worries about buying new mufflers anymore..... [/QUOTE]

Well, bugger me......now why didn't *I* think of that?! I just spent ages agonising about how to get the cowl on and off my World Models Super Sports Senior and the muffler was the problem. Geez, I could have saved myself some mucking around by just putting the exhaust deflector on the end of the stub :


_____________________________

MrBonk
http://www.mrbonk.com

(in reply to jnjones)
       Post #: 7

YS 91 Exhaust Problem - 6/19/2002 4:49:43 PM   
Steve Campbell2


 

Posts: 603
Joined: 12/5/2001
From: Baton Rouge, LA
Status: offline 		I'm curious about all these muffler problems. A buddy has a new 91FZ with no issues anywhere. I just got a new 91FZ. These engines do have the new, ugly muffler that has three bolts holding an end-piece on.

Is this the muffler you guys are talking about?

Steve

(in reply to jnjones)
       Post #: 8

YS 91 Exhaust Problem - 6/20/2002 12:10:34 AM   
jnjones


 

Posts: 2
Joined: 7/7/2002
From: Magnolia, TX, USA
Status: offline 		Elmshoot - I've tried high temp and red Loctite and neither held at all. In fact, with the high temp the muffler fell off right after I took off. I tried red hi temp RTV silicone and it held the longest but it still came off. Others have suggested using white teflon tape.

Steve - the last muffler that came apart was the the same as the one that you described. I bought it recently from Central Hobbies. However, my YS is an AC not the FZ. I'm not sure the FZ owners are having the same bad experience. Wiring it might be a good idea though, the replacement is $40.

How are you guys wiring the muffler so that it isn't lost? Do you have to drill holes in it? Is the wire attache to the motor mount are firewall? What type of wire are you using?

Last, will rubber hose ( used as an exhaust extension) take the heat put out by the engine?

(in reply to jnjones)
       Post #: 9

YS 91 muffler - 6/20/2002 1:32:39 AM   
SeanT



Posts: 79
Joined: 2/18/2002
From: Park Ridge, IL,
Status: offline 		The same thing happened to me.

To prevent in the future do the following:

Install your new tail piece on the existing muffler and tighten. Drill a small hole through both pieces approximately 1/8" from the joint. The hole should pass through the threads. Tap the hole for an appropriate sized allen head screw. Apply loctite to your screw and tighten it to the muffler.

No matter how much vibration the screw will not let the tail piece come off.

Sean

(in reply to jnjones)
       Post #: 10

Mufflers - 6/20/2002 1:48:21 AM   
Mike James



Posts: 2438
Joined: 1/19/2002
From: Anchorage, AK, USA
Status: offline 		Interesting...

I have a new YS .91 (FZ) and simply tightened it normally. (no locktite, wiring, etc.) That's with 15% fuel and an APC 15/6 prop.

I've test run the engine, removed and re-attached the muffler several times, and flew it all day last Sunday on my "Extase". ( http://www.nextcraft.com/rcpp_extase03.html ) No hint of it coming loose.

One thing I noticed while doing some propeller experiments...
The Master Airscrew props would bend, at high RPM, causing a LOT of vibration. The APC props are very smooth running, in comparison. Are any of you guys with the problems using props that "warp" at high speed? If so, a more rigid prop will help a lot.

Also, I've gotten really superior service from YS in the past. Have you contacted them?


_____________________________

Mike James
RC Design and Building - www.nextcraft.com

(in reply to jnjones)
       Post #: 11

YS 91 Exhaust Problem - 6/20/2002 2:10:23 AM   
jnjones


 

Posts: 2
Joined: 7/7/2002
From: Magnolia, TX, USA
Status: offline 		Mike - I have only used a 15 X 6 APC prop on this engine in this airplane. Previously, the engine was mounted in s Super Sportster 60. In that plane, due to height restrictions, I ran a 13 x10 APC prop and didn't experience any exhaust problems.

I did contact Performance Specialties (YS Engines) and they thought that either the engine exhust was getting too hot ( not enough air flow) or that at high RPM ( i.e. > 9,000) some sort of harmonic vibration was occuring. I believe the engine is getting plenty of air flow, so I'm going to experiment with different size APC props starting with a 14 X 10.

(in reply to jnjones)
       Post #: 12

YS 91 Exhaust Problem - 6/20/2002 2:48:02 AM   
jabowil-RCU


 

Posts: 186
Joined: 1/3/2002
From: Houston, TX, USA
Status: offline 		I have a 91FZ mounted in a Dave Brown soft mount. Using an APC 14 x 10. Probably have 25 or so flights on the engine. No problems with the muffler, but I'll check it before I fly again.

(in reply to jnjones)
       Post #: 13

YS 91 Exhaust Problem - 6/20/2002 6:49:01 AM   
mrbonk



Posts: 600
Joined: 2/18/2002
From: BundabergQueensland, AUSTRALIA
Status: offline 		For those of you not able to keep the muffler on and tight, you may like to try plumbers tape....you know, that teflon stuff they use on water pipe joints? I did this on both of mine and they're still exactly where I put them when I tightened them up. Just wrap 2 layers of the tape around the threaded ends of the stub (making sure you wrap it in the right direction of course, so it doesn't snag up when you try to screw it on) and tighten the whole thing up like normal. Works a treat No loctite required.


_____________________________

MrBonk
http://www.mrbonk.com

(in reply to jnjones)
       Post #: 14

YS Muffler - 6/20/2002 7:20:18 AM   
elmshoot