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Motorized Bicycle Trouble Shooting Use this area to post problems that may arise, if you could use some help in figuring out what is wrong with your engine and what needs to be done to achieve top performance.

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Old 09-10-2013, 08:04 PM
tdsears0627 tdsears0627 is offline
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Join Date: Sep 2013
Location: Illinois
Posts: 1
Default exhaust gasket keeps blowing out

I have an issue with the exhaust gasket keeps blowing out I replaced the stock studs with Allen head bolts I am using the voodoo expansion chamber exhaust, I put lock tight on the bolts and tightened the bolts until they wouldn't go any more and they are not bottoming out either ,

I guess my question is has any one else had this issue and how did you fix it, and is there a metal exhaust gasket out there or some other material than the cardboard type that came with it
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Old 09-10-2013, 08:18 PM
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2door 2door is offline
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Join Date: Sep 2008
Location: Littleton, Colorado
Posts: 16,271
Default Re: exhaust gasket keeps blowing out

Remove the exhaust and try this. Clean the gasket surface of the exhaust flange and 'paint it' with a magic marker or paint. Now rub it against a sheet of sandpaper laid on a known flat surface, glass is best, and you'll see the high and low spots that must be removed to get a good gasket seal.

The welding process when the flange is welded to the pipe warps the flange so you won't have a good flat surface where the gasket is supposed to seal.
Sand or grind the flange flat and see if this doesn't help preserve the gasket.

Also the gasket material needs to be something better than comes in the kits. I like to use gasket material made for exhaust applications and is at least 1/8" thick. Torque the fasteners to about 60 to 80 inch pounds then check the torque again after the engine has reached operating temperature a couple of times. Using gasket sealers is not necessary.
Longer or heavier pipes also need to be supported. Don't rely on the exhaust manifold fasteners only to keep the pipe secure.
Good luck.

Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"
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Old 09-11-2013, 10:58 AM
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crassius crassius is offline
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Join Date: Sep 2012
Location: USA
Posts: 3,074
Default Re: exhaust gasket keeps blowing out

after checking that mating surface is flat, also check that whatever you're using to support the weight of the exhaust is not pulling the pipe crooked on the gasket

also check obvious things like engine is loose and pulling away from pipe
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Old 09-11-2013, 12:03 PM
SuedePflow SuedePflow is offline
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Join Date: Jun 2013
Location: Coloma, MI
Posts: 49
Default Re: exhaust gasket keeps blowing out

I'll bet your flange isn't flat. Between being poorly cut from cheap, thin material, and then having a tube welded to it, my flange was far from flat when I got it. I ran it on a belt sander until it was flat and even across. And its been sealing with the same gasket since.
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Old 12-01-2013, 10:34 PM
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paintgun paintgun is offline
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Join Date: Nov 2013
Location: Illinois
Posts: 94
Default Re: exhaust gasket keeps blowing out

I just noticed today I had an exhaust leak on the bottom side of the connection to the engine. Thinking it might be either a warped flange or the cheap gasket burned through. Will check for trueness of the flange when I get a chance.
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exhaust, exhaust muffler, port

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