Exhaust gasket - fibre or copper

[hebdenwill]

Hi all,

Trying to put the exhaust back on my adopted 1994 Suzuki AH100. When I took it off the 'gasket' situation was as pictured in the two pics I attached - a flat, ringed hobby. Before taking the exhaust off I ordered a copper gasket for the exhaust off eBay, claiming to be for the right model of bike. This consists of a rounded ring with a seam in it.

The other complication is this - the exhaust won't fit on exactly flush as one of the holes has had to be retapped, meaning I've had to fiddle around with starting the bolts off in different sequences to get them in.

Would it probably be best to just buy a sheet of that thick fibre stuff and make the right shape as it'll be more forgiving and fill any small gaps better?

**Couldn't add the photos cause I'm using my phone but the gasket that came off is nearly flat, aluminiumish coloured and has two black poly / rubber rings embedded in its mating surface on each side**

[MCN]

Usually the ports feel high temperatures and require some sort of metal 'fire ring' to protect the edge of the gasket. (The hot gas can even cut through alloy head too in some applications.)

A silvered (not the element Ag) material is usual for exhausts.

The material will perform better if it can be crushed by the clamping force of the fasteners.
They don't get hammered up to ludicrous tension the nuts only have to be 'tight' Lock nuts are used because exhaust fasteners do not rely on the friction and stretch that keeps other fasteners in place.

Can you offer-up the manifold to the head.
Mark the tight spots and wallie out the holes that show any interference?
Battering it on can be ok but it puts the wrong sort of mechanical load on the parts and it may fail.

If you have a drilling machine you can open up the manifold holes using a masonry bit. (They need a cutting edge ground onto the 'percussion chisel tip so they cut. Masonry bits are designed to punch brick not cut it. 😂
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[WD Forte]

Fibre will last 10 minutes so that's not going to help much.
The seal will be copper or alloy or a mixture of that and some
asbestos substitute.
Your problem sounds more like the ill fitting collar not the seal
I'd offer up the downpipe and fit the bolt that fits easily then
position it to where it fit originally.

Next I'd use a pencil to outline the new bolt hole and see of there is enough material to enlarge the collars bolt hole in that direction with say a rat tailed file.
If so, good do that.
If not you'll have to get creative, Its not an unusual problem, there are various methods from slotting to welding, pics would help.
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