How do you fix the exhaust leak where the exhaust mounts to the engine?

I have a leak on my exhaust head pipe and burnt black fuel spits out of there and was told not to use RTV because eventually it'll get sucked it.

I also heard that this leak may be bad for the engine because it will make it run lean and eventually seize it.

I've had no problems riding so far with no seizing, but I'd still seal it; better safe than sorry. I haven't look at the piston and it has 60 miles of riding like this with an unsealed exhaust and I won't look at the piston unless something happens, but I hope it's still in good shape and will last me long. While it works I want to seal the exhaust head pipe area before anything major happens.

Does anyone have anymore information?
Does anyone have a solution?

I have a different kind of engine. I use a gasket for the head pipe. But the exhaust is held to the head pip via a spring. That's where it leaks, how do I seal that?

Would the aluminum foil break inside the gape and eventually get sucked into the engine?

Does it really stretch that much?

Is that silicone resistant to synthetic oil and fuel mixtures?

I have a different engine, a pocket bike engine. The exhaust mounts to the engine in a very similar way as the one in the picture. Where it leaks for me is, you see where the bolts are on the exhaust in the engine. Well that's the head pipe.

My exhaust is directly held to the head pipe by a spring and it has a nice gap between the exhaust and head pipe from where it leaks.
I don't know if that rubber will work because the exhaust goes over the head pipe.

Maybe a rubber that I can slide the pipe over and make it act like a o-ring?
But it needs to be a bit of a thinner rubber, and what material will work I don't know.

I heard silicone is not always resistant to fuel.

I recently checked SBP and the hose was $6 or $7 for 6" of it.

In that picture, is that a long hose or is that a metal pipe between the 2 "fatter" parts which are silicone hoses?
The first fatter part looks smaller in length than the second one and looks like it's holding loose, but correct me if I am wrong. It just doesn't seem long enough to seal.

I'll take a picture of my pipe tomorrow in the morning if I have time.

Sorry for the late pics, but here they are:
In the first image you can see what I use to cover the spits, it's covered full of black fuel after only a few rides. It's a white fiberglass based high temp piece of rope tide around.

The second and third pics show how the exhaust is mounted (what I was trying to explain, exhaust goes over head pipe). In the second pic you can see the head pipe, I can say that that thing is about 1/2" in length which is not much.

The outside diameter of the head pipe is almost 0.85".
Outside diameter of exhaust pipe where it goes over the head pipe is just about 1", a little bigger, but the increment is in the thousandths (1.00x"). The inside diameter of the exhaust is about 0.90-95" if I remember correctly, but that is still ALOT of play and room for spitting.



Right now I tried a method that I recently learned about: cut out a soda can shim and wrap it around the head pipe and then slide the exhaust pipe over the shim. It was hard to do it because it's a 4 hand job, but I did it with just 2 of my hands. I first tried doing 1 layer of soda can shim, but that did not seal very well.
This time I Dremeled down the inside of the exhaust with a straight carbide bit to make a slight taper (or chamfer) to be able to slide the exhaust over 2 layers of shims without damaging them. I hope 2 layers seals better.

What I'm concerned about right now is hoping that I didn't make the taper (chamfer) too deep in the exhaust pipe lol. If I did make that mistake then it would not seal as well as it should if it's deeper than 1/4"-1/2" deep of an angle (taper) because the taper causes the diameter to be a little larger on 1 side for a certain amount of depth just to be able to slide it over the shims, and then pushed on them where the taper stops. If the taper is too deep, it just wouldn't seal if that makes sense to you because the head pipe is only 1/2" in length so part of the exhausts ACTUAL inside diameter has to be there and pushed over the shims to seal (that's why I said the taper should not be deeper than 1/4" to 1/2" deep. It needs to be only deep enough to get the exhaust to slide over the shims, then it can be pushed onto the shims from the point where the taper stops. Where it's pushed on, that's where it seals because of the tight fit).
I'm trying too hard to explain this, but I hope you understand what I said.

See the problem with using the silicone hose is that the head pipe length is only 1/2" in length so not much room for the hose.

Hey you mentioned using foil right? Is that the same spot you use foil where I use shims?

Hmm, looks like foil is working for you but it is prone to breaking or bending just like the shims. (That's why I made a little taper).

If you are interested in knowing how I cut the shims straight I'll post a pic. Just let me know. It's very simple.

Where do you use foil? The flange where the black gasket is (in the pics)? Instead of the gasket you use foil there? It would be a little different on your engine, but that spot right?

Oh I see, I'll keep that gasket while it works. It does a pretty good job with sealing. Then if I need to I'd do what you did. Thanks for the tip.

If anyone would like to know how I cut out the shims straight this is how:
With a knife or scissors cut the top round hard part and bottom round hard part of the soda can completely off. This doesn't have to be precise and straight.
Then you can push/ bend the soda can flat, use a straight edge and a sharpie to draw a line across the soda can then a second line where you want to cut.
You can easily cut along the lines with scissors and you have a nice and straight shim.
It's going to look like a circle, so just cut it in half on 1 edge and now it's a straight line that you can wrap around anywhere you need to. The edges might be rough from the bend so you can cut a little bit off from the edge.
If the shim has bends and deformities on it, you can always rub something on it to make it straight if you know what I mean.

If you need pics to explain this little tutorial easier just request for them and I will take and post them.