Silencer Gaskets

[Tony H]

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.

[cymaz]

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 Flyer]

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 Cooper]

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.

B.C.

[Richard Clark 2]

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 McIntosh]

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.

[Former Member]

[This posting has been removed]

[wingcoax]

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

[Martin McIntosh]

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

[john stones 1 - Moderator]

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 T]

Sorry guys, but I'm going to break ranks on the 'thin smear'! 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 Christy]

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

[Robin Colbourne]

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

 

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 Flyer]

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 Welford]

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

[Steve Hargreaves - Moderator]

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...

[Nigel R]

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

[Guest]

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 - Moderator]

I created drawings of the commonly used muffler/silencer interface. OS/ASP/SC are all the same after all....it'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....