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Silencer Gaskets

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Tony H04/07/2020 23:26:58
870 forum posts
242 photos

Hi All,

I was wondering, sometimes 2 stroke ic engines come with a silencer gasket, does anyone use them? I dont usually because some engines done come with them and work fine.

cymaz05/07/2020 06:19:38
9281 forum posts
1200 photos

On glow 2t exhaust I use the thinnest ( and I mean thinnest ! ) smear of epoxy. Be very careful not to get any in the threads. Tighten up as usual. It will not leak or come lose.

To remove undo the bolts and give it a light sharp tap with a wooden mallet

Tim Flyer05/07/2020 08:04:23
1296 forum posts
236 photos

I would second that . For glow 2S exhausts epoxy. has the advantage that excess is burnt off in the pipe. If you use silicone it can block / restrict exhausts. Even so as said, a very thin smear is all that is needed. Removing epoxy is very easy with a heat gun.  Epoxied bolts can easily be undone after quickly heating with a soldering iron. 

Edited By Tim Flyer on 05/07/2020 08:06:06

Brian Cooper05/07/2020 10:05:40
566 forum posts
27 photos

Only use the gasket if you want the silencer to fall off. . . . and it will fall off.

Using a smear of epoxy seals the joint and, as a bonus, the silencer stays in place. yes


Richard Clark 205/07/2020 10:26:17
418 forum posts

Personally I think that as the average glow engine spews copious amounts of fuel containing 15-20% oil from both its carburettor and its exhaust a little extra leakage from the silencer joint doesn't matter.

Martin McIntosh05/07/2020 14:39:26
3471 forum posts
1216 photos

I use stuff called Kapton Tape which is similar to Sellotape to look at. Clean up one surface until oil free, stick on the tape then cut out the centre. This is almost totally heat proof, the only little snag being that it is super expensive. Luckily I happened to `acquire` a few rolls.

Steve J05/07/2020 14:54:21
1979 forum posts
54 photos
Posted by Tony H on 04/07/2020 23:26:58:

sometimes 2 stroke ic engines come with a silencer gasket, does anyone use them?

I use Granville Instant Gasket on the surfaces and threads.

wingcoax05/07/2020 15:18:04
104 forum posts
2 photos

Martin, i seem to recall using Kapton tape in coil winding.

Martin McIntosh05/07/2020 17:33:10
3471 forum posts
1216 photos

You are quite correct. It is/was used on car alternator windings which can get very hot.

john stones 105/07/2020 17:39:00
11595 forum posts
1517 photos

I tend to use them when supplied, not really had issues with manifolds blowing nor silencers falling off, blue threadlock is all I've ever used on bolts.

Mike T05/07/2020 18:01:25
524 forum posts
45 photos

Sorry guys, but I'm going to break ranks on the 'thin smear'! smiley I'm sure it works, but I usually put a small (but distinct) bead of 5-minute on one mating surface.

Dot it on with a toothpick/cocktail stick/barbecue skewer/whatever to form a small meniscus. Leave for 4.5 minutes then bolt up firmly but not super tight. The only 'smearing' involved applies to the oil put on the other mating surface (or not*). Leave a couple of hours to cure then apply the final 1/4 turn to fully tighten up. You'll get a gas-tight seal which can be easily dismantled with a tap when the bolts are removed.

*The last time I omitted the oil, tapping with successively large hammers had no effect and I had to resort to a blow torch to break the joint! (For reference: on a Moki 210 fitted with a Bisson Pitts muffler)

Peter Christy05/07/2020 22:57:10
1830 forum posts

Another +1 for 5 min epoxy.

I was taught this trick many years ago, and I've never had a silencer come loose or leak since adopting it! I do use a drop of threadlock on the bolts, but that's just to stop the bolts coming loose, not the silencer!



Robin Colbourne05/07/2020 23:59:20
605 forum posts
17 photos
Posted by Peter Christy on 05/07/2020 22:57:10:

Another +1 for 5 min epoxy.

I was taught this trick many years ago, and I've never had a silencer come loose or leak since adopting it! I do use a drop of threadlock on the bolts, but that's just to stop the bolts coming loose, not the silencer!




Pete, The only ways the silencer will come loose without the bolts themselves coming loose are:

  • A flexible gasket which gets squashed resulting in play between the silencer inlet and engine exhaust flanges
  • Distortion of the silencer or engine exhaust flange or mounting bolt holes
  • Stretching or thermal expansion of the mounting bolts or crushing of any washers

The reason epoxy works well is that it allows metal to metal between the flanges whilst sealing potential leak paths.

Threadlocking compound is good, but can attack any plastic parts onto which it finds its way. Plastic-safe threadlocking compounds are often little more than cyanoacrylate adhesive.

Most locking washers are virtually useless, as this video shows; hence the reason aircraft still rely on locking wire. locking washers have to be hard to retain their springiness, but will then chew up aluminium alloy and non-hardened steel, thus defeating their purpose.

Edited By Robin Colbourne on 06/07/2020 00:09:57

Tim Flyer06/07/2020 08:11:29
1296 forum posts
236 photos

Good post Robin. That Nord-lock system is clever. Those special washers are a great idea.

As you say the epoxy we use isn’t to glue the exhaust on , but simply to provide a rigid seal on imperfections in the manifold to crankcase contact. I’m quite surprised at the previous post saying the modeller attacked his engine with a hammer to remove the muffler. Maybe the castor in his fuel provided added adhesion?

The epoxy method for sealing manifold to exhaust flange has also been used by model boaters for decades. Boat exhaust systems are long as the include a tuned pipe with a silencer can on the end. As boat engines are mounted on rubber bushes there is a lot of movement in the engine and exhaust system. On boats a very good seal is needed ( or the boat fills with oil and smoke!) as the pipe and can have a fair bit of back pressure. The ability of the exhaust system to move with the engine without loosening is also required. A number of smaller model engines like Rossi’s now use a silicone washer and a spring clamp manifold to connect to the engine. This allows a bit of movement without damage.

Edited By Tim Flyer on 06/07/2020 08:24:16

Edited By Tim Flyer on 06/07/2020 08:28:09

Robert Welford06/07/2020 10:39:25
205 forum posts
4 photos

Yes - I use Nord-lock washers on petrol engine manifolds - they remain secure.

Steve Hargreaves - Moderator06/07/2020 12:05:55
6765 forum posts
197 photos

Have to say I always use a gasket on the muffler to manifold joint. I can't remember the last time one came loose on me. Use the correct gasket material & tighten the bolts correctly & it should be fine.

I contacted a local gasket company & begged an off-cut of Klingersil 4500....carbon fibre reinforced with a nitrile rubber binder...good for 220C continuous....

The Nordlock washers work well but they are a little wide to fit on the muffler screws unfortunately. Or at least the ones I have are...wink 2

Nigel R06/07/2020 13:57:36
3981 forum posts
714 photos

No, never used gaskets. I've just accepted a bit of leakage. Maybe I should use something.

John Laird06/07/2020 14:33:52
442 forum posts
57 photos

I Have used either thin brown paper - oiled then pressed against the exhaust port to get the pattern to cut out or a smear of silicone. Neither has caused any problems either from leakage or removing from exhaust when needed.

Steve Hargreaves - Moderator06/07/2020 14:46:58
6765 forum posts
197 photos

I created drawings of the commonly used muffler/silencer interface. OS/ASP/SC are all the same after's just the dimensions that change....

When needed I print them onto sticky labels....stick the sticky label onto the gasket material....a couple of minutes cutting around the template with a scalpel & a 3/4mm hole punch & Hey Presto! A new gasket emerges....

Happy to share the templates if anyone would like them...just drop me a PM with your email address & I'll whizz a copy over to you....thumbs up

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