Malleable gasket to connect exhaust to engine

Hi, my CB500 failed an MOT due to excessive smoke and noise at the front end of exhaust.

I have taken the exhaust off, and sicovered damage to the face of the o-ring joint that fits to the engine. The gasket had completely perished. Since the surface onto which I'd place the gasket is dimpled (through someone's hammering), I'm concerned that a solid gasket e.g. Copper, won't affix neatly, and have therefore considered solutions such as using a liquid/ instant gasket (eg silicon / gun gum or similar), but would prefer to put on a physical gasket which would be slightly malleable and therefore neatly squash/ fit neatly into the unnecessary grooves on the o-ring.

Grateful for your thoughts and support

Firstly, congratulations on getting it off - that's the hard part done.

The proper copper gasket isn't a flat gasket. It does have an element of 'squash' to it.  Could you grind the face flat perhaps? Hard to know without seeing how bad the dimples are.

I tried those Fibre Gaskets on my exhaust and did not seal properly, then I ordered the Copper one, when I saw them, I thought they are not going to seal, but they did, since my experience I would always recommend the Copper ones.

Many thanks for the prompt and helpful response. It’s good to know the copper gaskets have some ‘squash’ capability. I have used a metal file to get the ‘face’ as flat as possible without damaging the o-ring itself. See attached pic.

Another concern is that one of the lugs has been sheared off. I’m hoping that three of four lugs screwed in, plus two anchor points on the exhaust, plus new copper gaskets will prevent any more noise and smoke and that I’ll get this ‘94 model through the MOT. Thanks again

Oops I tried to attach two photos and copied it many times. Sorry!

Copper gasket and instant gasket.

Smeer the head with instant gasket, then place the copper gasket on top of it making sure it's centred, then put some more instant gasket on the exhaust collar then just refit the exhaust. To I think 14nm

Just to clarify... you’re suggesting a thickness of 14mm, comprising the copper and instant gasket combination, yes?

Have other people found this combination to be effective?

14nm (Newton Metres) is a torque setting,  i.e. how tight the bolts should be.

James suggestion makes sense as the gasket paste will fill the dimples and give a better seal than the copper alone.

What golly said

DGW.Honda wrote:Oops I tried to attach two photos and copied it many times. Sorry!

Fixed it for you now

when I replaced my manifold gaskets I was on with the job of re -spraying the down tubes and at first I thought that there wasn't any gaskets in there I had to get a torch and a sharp scriber and dig them out and by this time they were a mess anyway so were replaced by new ones

I suspect if you haven't got any instant gasket you could use exhaust paste to equally good effect: smear it on the copper gasket before fitting.

On the subject of your snapped stud: if the exhaust won't hold onto the engine with only three studs/bolts then you could use some thin-ish wire wrapped around the engine to try and hold it in place a bit more - it will be an horrific bodge, but the MOT man can't fail you for bodges, as long as they are safe.