cutting new gaskets

kainbanford

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Jul 15, 2008
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So my bike has been leaking/splattering/whatever some black "goo" from around the exhaust gasket (where the exhaust bolts onto the engine). I tightened the bolts, but it's still doing it.

I bought some gasket material at AutoZone, cut a piece out, and then I noticed that the gasket I was replacing was covered in a thin sheet of metal.

I didn't have anything like that, so I put the old one back on. Do I need to figure out how to "sheath" my gaskets in metal before I put them on the exhaust? Should I go and use something like unrolled and flattened pop can, or would a couple of layers of tin foil work OK?
 

Skyliner70cc

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Nov 17, 2007
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1,338
I'd buy OEM gaskets from a vendor. They work pretty well. I'd also replace the studs and bolts with US made ones so you can torque down that muffler.

Also make sure your muffler flange is flat, if not file it so it is and allows better seal.
 

BoltsMissing

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Jan 31, 2008
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What Skyliner suggest is the same as what I would have said to, I had same issue and took it to a exhaust place to get advice.

When you cut out a new gasket or replace it with a HT gasket, fasten the gasket by itself on the engine's exhaust port. If you don't a have a dremel, use a file and shape the centre hole the same shape as the port hole.Try and get it as exact and clean as possible so the gasses flow past the gasket on not on to it which causes it to fail cos it's "bombarded" with exhaust gas.
Use your fingernails to feel the inside of the gasket faciing the port hole and file away till it's level.


I use Stag for sealant and now wait till the next day ( 24 hours no less) so it drys completely. I used to think the heat from the exahaust soon after I start it will dry it out anyway, this did not work, it still leaked.

Then it needs to have the expansion of the flange taken care of so it don't warp, causing it to leak, and this what the exhaust place suggested.
A "heat sink" can be tried.
Replace the stock studs with longer Socket Head wrench screws ( Allen Key bolts) and use spring washers, flat washers and use the old nuts to take up the space. This transfers the heat away from the flange plate and apparently reduces the tendency for it to warp.
 

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fatboy67

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Mar 29, 2008
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107
Hey bolts you wrote to fasten the gasket to the motor wouldn't that get all **** inside the motor??
I bolted it to the exhaust and filed it out to the same size as the exhaust. The exhaust port is smaller than the engine port, Yes I know this,, but If you make the gasket the same size as the engine port the gases are still going to hit the steel exhaust. Or is there more to it than that???
To seal it I just used normal silicon you will find that normal roof silicon is rated at up to 300 Degrees.Just leave it over night and it should be fine.
I just used the gasket that came with the kit just make sure you seal it, And Also make sure the face of you exhaust flange is true. I had to true mine up. I put a straight edge across it and I could see that it sagged in the middle.
Mine is about 5-6 months old and I ride it every day to work, well most day depending on the weather.
 

BoltsMissing

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Jan 31, 2008
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895
Hey bolts you wrote to fasten the gasket to the motor wouldn't that get all **** inside the motor??

Emm, yeah so you stick a bit of rag while doing the job. I had some acetone and wiped it all clean, clean as new.

The exhaust port is smaller than the engine port, Yes I know this,, but If you make the gasket the same size as the engine port the gases are still going to hit the steel exhaust. Or is there more to it than that???

Yes, but what I aiming at, is to eliminate restriction due the gasket being not cut right. As far as the next path of gas travel as it enters the pipe, yes it is smaller, on this particular new engine I tried this on I let it go, the only objective was the gasket.
I think the "more to it" is I figured to leave the pipe hole as it is, and not mess with it and get whatever I can get to retain "back-preasure".
It worked ok on initial fire-up of an new HT, and I also did the same with the carby gasket,and not messed with any other metal bits.
Only the gaskets concerned me at that point, easy stuff.


To seal it I just used normal silicon you will find that normal roof silicon is rated at up to 300 Degrees.Just leave it over night and it should be fine

Personal choice, I never liked silicon on engine builds, except now the CDI is covered with a thick layer and where it's needed for the electrics/wires on a HT.
Been using Stag for well over 30 years on almost everything, including the gas threads on a BBQ bottle.
The other type of gasket stuff I use if the job requires it is hard setting gasket stuff, looks like vegemite.

I had to true mine up. I put a straight edge across it and I could see that it sagged in the middle.

Yep, every pipe I have had so far from a kit needed truing. I now use the side of a grinding wheel to get it as best as.
I'd like to hacksaw it off and put my own cut out, one day,but since the heat sink idea I have never had a problem since.
 
Last edited:

kainbanford

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Joined
Jul 15, 2008
Messages
4
I'd buy OEM gaskets from a vendor. They work pretty well. I'd also replace the studs and bolts with US made ones so you can torque down that muffler.

Sure sure, jump to the easy and reasonable solution. Duh, I always try to make things more complicated than they are. I'll order one up!

Also, good tip about the gasket sealant and verifying that it's totally flat. I'll check that out too
 
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