Muffler gasket?

You don't need any gasket, that just tends to make the muffler come loose in flight, a rigid attachment is better. You can also use split washers on the screws in order to stop them from coming loose.

I looks like you have a Thunder Tiger muffler on there though (.10 or .15 GP), instead of the original OS muffler?
It should be fine too but it likely explains the error in the screw length.

Ya ...was a gift. Not sure whats what!  Screws don't come loose,they're just bottomed out before the muffler is tight! Lock washers WOULD probably make up the difference. Don't know where I can find any this tiny though. Muffler IS a perfect match to exhuast port.

I usually make a paper gasket by pressing the muffler onto the paper and cutting it out with scissors and a scalpel. Might not look pretty but works great!

My OS Max .15FP-S (control line version with venturi & NVA) came with same type muffler, supposed to be quieter. I had another OS muffler I bought some time later that didn't have the second chamber and used it, slightly lighter but with a little more noise. So, this type muffler wasn't limited to Thunder Tigers alone.

I have the Thunder Tiger .15 R/C plain bearing engine prior to their Magnum series coming out, appears to be a copy of OS earlier Schneurle prior to the FP's. Thunder Tiger used a larger venturi on their R/C carb, and kind of fickle with feed, liked the OS carbs better, seemed to always work. No complaints about Enya's, too.

Can't say what mufflers OS supplied overseas to Europe, could have been a little different.

If one is concerned with muffler joint to engine burbling with Castor, could use a little temperature tolerant RTV silicon sealant. Then seal it tight with RTV sealing imperfections. I like Permatex Ultra Gray, because it covers well even in very thin coats, used in automotive transmission cases and covers, motorcycles, etc. But, everyone has their own methodologies and preferences, some with more success than others.

Good advice all around here, but I wouldn't rely on
any of them to make the muffler secure. Cut, grind,
or get a shorter screws, so the muffler can be tightened
to the exhaust port without counting on a gasket to
take up the looseness. Then you can use a gasket to
seal if you like. All aside, a couple of split washers might
do the trick too. Nice engine.
Bob

I agree with the washer idea, it also makes good engineering sense. One flat and one lock washer, the lock washer goes against the screw head.

Go to you local hardware store. They should have washers of that size for less than a dollar for all 4.

These are really tiny screws and no room for a washer thats any larger than the diameter of the screw head . I have thought of just shortening the screws,but hard to maintain the entegrity of these very fine threads.

The washers are out there. They come standard from the factory with them. I think...

Anyway if you don’t want to bother with washers just go pick up shorter screws. That way you don’t have to worry about messing up the threads.

OhBee wrote:These are really tiny screws and no room for a washer thats any larger than the diameter of the screw head . I have thought of just shortening the screws,but hard to maintain the entegrity of these very fine threads.

I'm sure if you went to an established, real hardware store, and
showed them the screw, they might come close for washers.
You could also determine what size washer you need, and go to
a site like https://www.microfasteners.com/ , or McMaster Carr,
and just order them. If you scour the net, you might find the
parts call-out, which might list the screw specs needed.
Maybe something like one of these. https://www.microfasteners.com/home.php?cat=662
Keep us posted, OB.
Bob

I always use muffler gasket .
With new gasket, I retighten muffler mounting screws  after first run.
Works like a small vibration damper, crankcase/muffler ,never lost one muffler in flight.
Every engine Manual tells you: use muffler gasket, for good reason.
Found very GOOD QUALITY + FAST SERVIVE @

http://icbimproducts.com/gaskets/newcart/viewitem.php?productid=1

Buddy

germanbuddy wrote:
Every engine Manual tells you: use muffler gasket, for good reason.

Really?
I don't remember ever seeing that from OS or Enya.
Might have seen it for possibly for a Thunder Tiger engine....

I seldom use a gasket except on pipes which is important.  I found that a very fine flat single cut file rubbed over the machined exhaust surfaces flattens out the chatter marks from machining.  Just use your thumb pushing against the centre of the port and move the file back and forth maybe 1/4" to take the tops of the ridges off and you can see when you have filed enough.  Leave witness marks and don't round the surface.  I have not lost any mufflers either. RC carbs on the LA .40s sometimes come loose. I usually drill out the exhaust hole and turn away the baffle on the LA .15 mufflers too if the club field allows it.  The .10 and .15 motors are not too loud usually.   I think you may have a problem with most local hardware stores getting the bolts.  They are 2.5 mm dia. I think, not the usual M3.  LA .15s can really rock for what they are.  We run them without mufflers for racing, and you get pretty dizzy on the Goodyear racers and Clown racers.

Generally Japanese engines are machined so well that a muffler gasket is not necessary. I know that none of my Enya or OS engines use them.

Grind a tad (1 tad= 1/16th") off of screw, use some Loctite and go fly!

If gaskets arn't used,wonder why they are available?

OhBee wrote:If gaskets arn't used,wonder why they are available?

If the surfaces of engine and muffler are well machined to a high degree of tolerance and have a perfect match then no gasket is necessary any. Some engines have low tolerance, so a gasket needed.

Well, I can confidently say that the small lock washers are out there as I have just received an OS LA myself today, and my screws have little lock washers on them the same diameter as the head. However, like yours, my screws are too long. Not my first rodeo, but I will be chopping my screws down some. I would but new ones, but the LHS does not have them in stock anymore, and cutting them is relatively painless, but I have also done it before. I know you *should* have a nut beyond the cut so you can 'chase' the threads clean after. I do not have a nut, so I just carefully roll the screw around the Dremel cutoff wheel so as not to have as 'hard' of an edge. When done, I also roll the screw on the cutting disk to put a very slight bevel on the screw and I feel it also aids in not having the screw threads cause any problems.

Here is a picture.

What size is that "allen" head? I had nothing that small and had to find another way to loosen them.

Sorry, I cannot tell you that. I don't usually use Allen keys. A little thing I do and use are Torx bits. I am just laying down using my tablet, but I can see what size Allen key tomorrow for you if you like.

Appears to be 2 mm to me. I've never had the need for an allen wrench that small and I was a Honda motorcycle service tech for 42 yrs. 2 roller cabinets full of tools!

A standard metric Allen key set will go down to 1.5mm, which is needed for smaller engines (e.g. the MP Jet .061) using M2 screws. On electronics you'll often need even smaller ones...