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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › RTV silicon in your engine...
07-23-2012 07:32 PM  8 years ago
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RyanW

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Edmond, Oklahoma

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RTV silicon in your engine...
I personally don't like using RTV silicone for exhaust sealing because it can and will (no matter how careful you are) get into your engine.

I have some of the old KSJ muffler gaskets that I love dearly, but you can't get them any longer (that I know of) and the only ones I have are for 90 size engines. In a moment of wander, I used the silicone. I used a prepped Q-Tip to remove about 1mm of silicone from the inside edge of the flange (this usually provides enough "squish" room).

I fired up the helicopter for the first time and poof, she died about two minutes into the flight. Auto'd down.

Checked everything, but she wouldn't start. Pulled the plug and found this. Yep, a piece of RTV silicon. Put a new plug in just to see if she would fire and she did, but only ran about another minute before doing the same thing. Now I am pulling the engine and cleaning it out thoroughly. Should have listened to my own advice!

-Ryan
Mikado USA, Kontronik, Opti-Power, MKS Servos
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07-23-2012 07:39 PM  8 years ago
YSRRider

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usa

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you dont really need any sealer. quick shot of brake cleaner after flying will clean off any oil. OR windex and an air compressor.

RTV is pretty thick and hard to apply on these motors. HONDABOND and YAMABOND from your local bike dealer are a better alternative. YAMABOND comes in different styles. One is soft, the other dries hard. Either way, they spread really thin and you should have no issues with them.
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07-23-2012 07:41 PM  8 years ago
dkshema

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Cedar Rapids, IA

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You don't need a gasket between the muffler and motor. No RTV, no epoxy, no aluminum or fiber material. Nothing. Not even on a motor that depends upon muffler pressure into the tank to improve fuel flow.

Your YS uses tank pressure, but that comes from the motor via the backplate nipple and check valve, not from the exhaust.

Both mating surfaces are flat and smooth (especially if it's a new motor and muffler.

What are you really trying to accomplish via the gasket, anyway?

Use an allen wrench that fits the socket heads well, tighten down the bolts good and tight. Go fly, land, and while still hot, tighten again. Repeat one or two times, the muffler will stay put till you want to take it off. Simple, free, and leaves no nasty residue.

You may want to clean out the muffler before putting it back on, as bits of RTV may have also gone there and are lurking, waiting for their chance to attack later on.
-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz
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07-23-2012 07:44 PM  8 years ago
fla heli boy

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cape coral, florida

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I used to use the copper high temp stuff (Permatex I think it was)for exhaust manifolds and never had an issue.
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07-23-2012 07:51 PM  8 years ago
Ace Dude

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USA

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I had the same thing happen once with regard to a piece of silicon in the glow plug.

I don't use anything anymore and it works just fine. One less headache to worry about.
  
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07-23-2012 08:46 PM  8 years ago
BladeStrikes

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Shelby TWP,Mi

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RyanW,
You do need a gasket or a good gasket Adhesive.Having a air leak where the pipe/block meets is no different than having the head come loose which will blow the motor,seen it happen too many times..If you have a tiny leak where the pipe bolts to the block,you'll start getting a dark spot on the piston..If you look at alot of pics where pistons broke,90% of the time its on the exhaust side because it had a leak.Either use the Aluminum gaskets or 3M gasket Adhesive.
I like the gasket Adhesive because it pretty much glues the pipe to the block.When I take the bolts out,the pipe is still on and doesn't fall off..Just use a tiny bit on the out side/lip of the pipe and put it on right away as it drys fast..

BTW,
its also very easy to clean off.It also doesn't matter if its a OS/YS motor because a air leak is a air leak with either.
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07-23-2012 08:53 PM  8 years ago
reddragon

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Brooklyn, N.Y.

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How much sealant does one apply when when they use the RTV? Do you wait some time for it to cure our do you apply it and then immediately attach the muffler so that it will squeeze out, break off and cause a flame out? I have never had a failure in all the years I have been using it and my coat is THIN.Wayne - Fly it like you stole it! You're in good hands with Runryder!
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07-23-2012 08:55 PM  8 years ago
BladeStrikes

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Shelby TWP,Mi

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BTW,
If you have a air leak where the pipe meets the block,i also effects power..
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07-23-2012 09:10 PM  8 years ago
fla heli boy

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cape coral, florida

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I can't remember why now, but I used to cut metal gaskets from fairly thin aluminum and put copper high-temp on both sides of the plate and bolt it up. You had to unbolt it and literally PEEL that muffler of the block.
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07-23-2012 09:14 PM  8 years ago
adamsz06

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Geilenkirchen Germany

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Sounds like the aerosol Permatex copper I use on v8 header gaskets...R.I.P. Roman
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07-23-2012 09:24 PM  8 years ago
RyanW

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Edmond, Oklahoma

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I have ran no gaskets on two engines. One was an Italian engine that no gaskets anywhere on the engine... the surfaces were that precise.

The second one I took a mirror, wet/dry sandpaper (super fine) and a little oil to get a nice figure of eight swirl pattern on the muffler flange. That worked well if I recall.

As everyone has said before, you DO NOT want their to be a gap in the seal on the muffler.

When I used sealant previously, I always spread it with a new razor. I would run the silicone so thin you could see through it. Then I would run a Q-Tip to get it away from the edges.

Okay, tear down time!
-Ryan
Mikado USA, Kontronik, Opti-Power, MKS Servos
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07-23-2012 09:57 PM  8 years ago
BladeStrikes

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Shelby TWP,Mi

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Ryan,
The problem is---> Silicone turns into rubber when it drys and stays that way for a long time.If you have a tiny,tiny air leak thats its blocking,it will suck some into the engine sooner or later..
Thats why I like useing the 3M stuff,it doesn't do any of that.
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07-23-2012 10:26 PM  8 years ago
McKrackin

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Lucasville,Ohio

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Just an FYI but almost all pistons that get a hole in them or break will break in the exhaust port just because that's the hottest point on the piston.

It confused me for a while until a mechanic told me that.

Any two stroke that ruins a piston will do it right in the exhaust port.

Exhaust leaks are bad though...I have started using Align muffler gaskets and it made a big difference....Much cleaner and dryer too.
I literally never use the word literally right.
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07-23-2012 11:13 PM  8 years ago
ticedoff8

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Morgan Hill, CA. USA

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I have the Hatori pipe / header on my YS 91SR-3DS engines (on two helis).

Then, I use the 2-part thermal epoxy that I get from HeliExpress / Grand RC. It is the same epoxy that you use to cement the thermal-couple for head temp & SmartCarb sensors.

I mix up a small batch, smear it around the exhaust opening on the engine and add a little dab inside each of the 2 the bolt holes where the muffler bolts through.

Then, mount the header for the pipe (assuming it is a 2-part muffler / header). If it is a 2-part muffler / header, I will leave the header attached for all normal heli maintenance / crash repair.
It is a last resort to remove the header, just because I don't want to run out of epoxy.
But, the bolts come out easily and the header will "snap off" with a little side load. I will clean up with a wire brush, and it is ready use again.
There are a few benefits:
* Better heat transfer from the block to the header;
* Contour the header to the exhaust port for a better flow;
* Seal the exhaust the header so the "tuned pipe" effect works correctly (assuming it is a tuned pipe / muffler).
* 0-Chance the muffler / header will unbolt in flight

Having said this, I've also used the side of a Coke can (thin, soft aluminum) to cut a header gasket. It is pretty easy to do.
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07-23-2012 11:24 PM  8 years ago
airdodger

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Johnston USA

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Mckrackin The hottest place is the ring gap it breaks the continuity of the heat path. Most pistons showed seizure at the ring end gap. I have ruined a lot of two stroke pistons and most were not stuck at the exhaust port. I have had pistons that were concave after a run, but not seized anywhere.

You can run an engine without an exhaust, it will run fine. LOUD though. The old Enya engines had only a metal piece that opened or restricted the exhaust.
Chris
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07-23-2012 11:34 PM  8 years ago
wifeorheli

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reno, nevada usa

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I have been using RTV for my muffler forever its even reccomended by bobby watts. Since i haver switched to rtv i have had zero problems with leaking. If installed correctly you will be fine. the key here is a "VERY" thin layer.Novarossi Motors U.S.A
www.PLanethobby.com
Team GrandRc.com
Team Byron Fuels
ZRC U.S.A. "PushGlo, SwitchGlo"
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07-23-2012 11:42 PM  8 years ago
McKrackin

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Lucasville,Ohio

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Mckrackin The hottest place is the ring gap it breaks the continuity of the heat path.
That makes sense too but only adds a second reasonable opinion to the first I heard.

I can't go over it word for word but it was a very educated and well thought out explanation that he used text books to reinforce.

I think I believe you both
I literally never use the word literally right.
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07-23-2012 11:52 PM  8 years ago
jschenck

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La Vista, NE.

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I've been putting RTV on the last number of muffler installs. I put it on so thin that you can't see it on the metal. I also don't put any right next to the inside edge. My primary purpose is to keep the oil from leaking out but I would imagine it does help with keeping mixture adjustment tuning.
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07-24-2012 12:49 AM  8 years ago
wifeorheli

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reno, nevada usa

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Without a good seal your gonna be chasing needles all day long(this is with muffler pressure systems) all i can say is try it and use a thin layer. Gaskets are a pain problem is they WILL end up breaking down.Novarossi Motors U.S.A
www.PLanethobby.com
Team GrandRc.com
Team Byron Fuels
ZRC U.S.A. "PushGlo, SwitchGlo"
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07-24-2012 12:59 AM  8 years ago
Havoc

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Ky.

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I use a very thin smear of five minute epoxy. Works great a readily available. Any excess melts away harmlessly. Generally it takes a little knock to remove the muffler too. Before that, I did the RTV thing but eventually had it take out a plug.
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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › RTV silicon in your engine...
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