Exhaust gaskets burning up

[GasX]

I have the phantom bikes exhaust on my 4 stroke and while I love its look and sound, I have burned up two exhaust gaskets in quick succession. The first was the stock one with the exhaust and the second was a BGF gasket with metal on both sides of the gasket material (as recommended by phantom...)

What are the possible causes of this?

I have a hunch that my bolts are too long and the gasket is not getting compressed. A tiny air leak here might cause it to burn up, yes?

 

[2door]

It's easy to check your bolt length but my guess is the gasket surfaces aren't laying flush against each other. One or both might have a warp which will cause the problem you're having. This is very common on the Chinese 2 stroke pipes and mufflers but it might also apply to your 4 stroker.

Start with the muffler or exhaust pipe flange. Clean it then paint it with a broad tip magic marker and run it across a sheet of course grit sandpaper that is laying on a sheet of glass or any known flat surface. You'll quickly see if there are high/low spots that are keeping the flange from fitting flush to the gasket and cylinder. You can check the cylinder gasket surface by placing the sandpaper on a flat file and running it across the exhaust port. (plug the port with a small piece of cloth or paper towel to keep grit out.)

Let us know what you find.

Tom

 

[MEASURE TWICE]

http://catalog.remflex.com/SearchResults.asp?Search=gasket+material

http://catalog.remflex.com/category_s/154.htm

I saw this in a search and maybe it works well for high heat. It is supposed to compress up to 50% and not shrink under heat.

For my exhaust I used some high temp material that said it was good for exhausts and it burned up. Also the asbestos stuff same thing happened.

Graphite is supposed to be to 2000 F.

They say return it if fails, I hope it does not disintegrate, cause then you have nothing to return for refund.

I ended up making copper gaskets. Think copper sheet drilled and cut up did it for my application. It was a bit extra work as I needed a thick gasket as I am using flex copper water pipe end fittings and the thickness to replace the rubber gasket is much more than the normal exhaust flange type gaskets.

I made 20 of these and put 10 on the exhaust port and the other end from pipe to muffler and so far so good.

See page #6 post #58 pictures of the copper exhaust gaskets I made:

http://motorbicycling.com/showthread.php?t=29678&page=6

MT

 

[Fugi93]

I just used Permatex black. That was 3000 miles ago. I just let it set up for a few hours before I tighted it all the way down. I didn't use any gasket at all and no problem since.

 

[GearNut]

Get yourself a heat riser gasket for an old 50's thru 70's VW. They cost me 99 cents at the local VW hot rod shop. You can't beat the quality of them. All metal construction with a crush ring around the port hole. They match up with the HuaSheng exhaust studs and port perfectly too.
Definitely check the exhaust pipe flange for true flatness as 2door suggested. A warped or curved flange will make it nearly impossible for any gasket to reliably seal up.

If you suspect that the bolts are too long, check for that by temporarily attaching the exhaust to the cylinder head without any gasket in place. You should be able to get the exhaust to tighten up before the bolts stop turning.
If they are too long, don't get replacement ones that are much shorter. You want as many threads of the bolts to go into the threads of the cylinder head as possible, nearly but not quite bottoming out.
Mine came very close to bottoming out, but I added 1 split lockwasher to each bolt and the fit is now perfect.

 

[thatsdax]

Your Flange is getting lose.

 

[d_gizzle]

Gearnut,do you know of any websites selling that heat riser gasket?

 

[GearNut]

http://vwparts.aircooled.net/Preheater-to-Muffler-Gasket-Large-Hole-1963-74-p/113-251-263.htm

 

[d_gizzle]

Thanks for the link and the super-fast response. Ill be getting that soon.

 

[GearNut]

You are welcome. As to the super fast response, It was just blind luck I was here at the right time when you asked.

 

[2door]

You are welcome. As to the super fast response, It was just blind luck I was here at the right time when you asked.

Don't let this guy fool you. He lives on this forum and just sits 24/7 and waits to post.

Tom

 

[GearNut]

I DO NOT!
neener neener neener

 

[d_gizzle]

Hey I can't say nothin. I got my email synchronized with my phone just because of this obsession.

 

[mat_man]

What are the possible causes of this?

Check your plug.

too lean = too hot = burning/warping/blowing up engine parts like pistons, rings, and valves.

 

[GearNut]

A lean burn wouldn't cause exhaust gaskets to burn up/ blow out.
A warped header flange, non reinforced exhaust gaskets, or a combination of both certainly will though.

mat man, you are totally correct about a lean burn frying internal parts though.
I'm not trying to diss you here.

 

[mat_man]

I would spray some soapy water on the gasket/flange to find any leaks. (only when motor is cold).

Many exhaust have spark arrestor fine screens that tend to get clogged. This would
give back pressure. I would take the screen out

 

[locutus_1]

copy the exhaust gasket to a 1/8 thick aluminum sheet and cut it out.. then adjust your carb you are running to lean.. its over heating your engine causing it to burn out