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Home✈️Aircraft🚁HelicopterAlignT-REX 700N › YS 91 pipe keeps loosening up
09-23-2018 07:40 PM  3 years ago
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jasonrusso

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Haverhill, Massachusetts

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YS 91 pipe keeps loosening up
I've been flying the 700n with the YS 91 SR with Hatori pipe for 5 years without issue. A month ago, the pipe loosened up (flange was tight). I put new bolts in, got 2 flights and it loosened up again. Put new bolts in again, first flight loosened up!!!

What's the deal? I don't think it's the pipe, maybe engine bearings causing a vibration? The engine runs well.
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09-23-2018 08:38 PM  3 years ago
NQNA

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USA

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Buy some Dynalock washers. They will not become loose. I use them on all muffler bolts and other high vibration applications. Below is a link to some washers at Microfastners. There also is a brand called Nord-Lock available online and on Amazon. I’ve used both brands.

https://www.microfasteners.com/dynalock-washers.html
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09-23-2018 10:42 PM  3 years ago
jasonrusso

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Haverhill, Massachusetts

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NQNA Buy some Dynalock washers.
3mm? Any idea where I can find the silicone spacers in the hatori pipe? The fell out when the pipe got loose.
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09-24-2018 12:31 AM  3 years ago
NQNA

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USA

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09-24-2018 01:31 AM  3 years ago
wjvail

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Meridian, Mississippi

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Another directions... Make certain the mating surfaces between the exhaust and the muffler are really flat. At times in the past, when I've had a muffler that loosens up, I've found that the "ears" of the muffler have distorted or worn enough that there isn't a very flat mating surface to the engine. By ears I'm mean the area nearest the mounting bolts. Similarly the outer edges of the engine exhaust can wear and not mate evenly with the muffler.

The solution has been to take some wet/dry paper mounted to a gauge block and re-level both the muffler and engine exhaust mounting port.

Errr... now that I think about it, did you mean the 4 screws that mount the muffler to the flange or the two screw that mount the muffler to the engine. I'm about to confuse myself.
"Well, nothing bad can happen now."
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09-24-2018 02:32 AM  3 years ago
jasonrusso

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Haverhill, Massachusetts

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wjvail Another directions... Make certain the mating surfaces between the exhaust and the muffler are really flat. At times in the past, when I've had a muffler that loosens up, I've found that the "ears" of the muffler have distorted or worn enough that there isn't a very flat mating surface to the engine. By ears I'm mean the area nearest the mounting bolts. Similarly the outer edges of the engine exhaust can wear and not mate evenly with the muffler.

The solution has been to take some wet/dry paper mounted to a gauge block and re-level both the muffler and engine mounting port.

Errr... now that I think about it, did you mean the 4 screws that mount the muffler to the flange or the two screw that mount the muffler to the engine. I'm about to confuse myself.
Yes, that is not the case here. The flange mounts to the engine, that is still tight. It's the pipe that is falling off.
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09-24-2018 08:25 PM  3 years ago
ticedoff8

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Morgan Hill, CA. USA

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Check out Grand RC for Hatori parts
http://grandrc.com/advanced_search_....x=0&search.y=0
+ > ÷
Believe 1/2 of what you see and none of what you hear.
Fake News will be the downfall of our Republic!
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09-24-2018 09:20 PM  3 years ago
balsapro

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Gallatin,TN

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Just throwing this out there... If the engine has been in service for a while you might check the rear bearing if its going bad and creating some bad vibes could cause the pipe to loosen.Build the Best, Fly the Best, Crash the Best
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09-25-2018 02:53 AM  3 years ago
wjvail

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Meridian, Mississippi

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jasonrusso Yes, that is not the case here. The flange mounts to the engine, that is still tight. It's the pipe that is falling off.
I see now. Try replacing the two large o-rings. They are something of a consumable. If you've been flying a lot and have a lot of time on the muffler you may need to refurbish it. I'd begin by replacing the rubber parts and since you're at it, I'd look at replacing the little aluminium spacers that go in the silicone grommets.

I know - it's a muffler and doesn't have any moving parts. Still, Hatori 2-piece mufflers need freshening-up occasionally.
"Well, nothing bad can happen now."
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09-25-2018 03:04 AM  3 years ago
jasonrusso

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Haverhill, Massachusetts

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wjvail
jasonrusso Yes, that is not the case here. The flange mounts to the engine, that is still tight. It's the pipe that is falling off.
I see now. Try replacing the two large o-rings. They are something of a consumable. If you've been flying a lot and have a lot of time on the muffler you may need to refurbish it. I'd begin by replacing the rubber parts and since you're at it, I'd look at replacing the little aluminium spacers that go in the silicone grommets.

I know - it's a muffler and doesn't have any moving parts. Still, Hatori 2-piece mufflers need freshening-up occasionally.
I already ordered 2 parts kits from China. It comes with all the grommets, orings, etc.
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09-26-2018 06:14 AM  3 years ago
wjvail

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Meridian, Mississippi

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Please post if you find a solution to this problem."Well, nothing bad can happen now."
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09-26-2018 11:15 AM  3 years ago
jasonrusso

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Haverhill, Massachusetts

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Well, the Chinese guy I was ordering the parts kit from cancelled the order. I really don't want to have to buy a whole new pipe because the silicone and aluminum spacers are gone.
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07-23-2019 09:21 PM  27 months ago
Rob43

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Midland, MI USA

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I am thinking the MRCI exhaust may be compatible with the YS. I thought I read that somewhere. If so, the accessory kit they list may be the same thing as needed here. Unfortunately, for the moment, I see that both AMAIN and Helidirect have them, and are both on backorder. Something to check.

https://www.amainhobbies.com/mrci-m...cc-1310/p754645
https://www.helidirect.com/collecti...ccessories-1310
Rob
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