In spite of cleaning and assembling carefully with a new gasket and paste there is still a weep from the exhaust where the pipe meets the exhaust ports. Has anyone got advice on how to fix it? So far as I can see the flange on the pipe is in good condition so any tips welcome.
I always bolt up the flange to the head before I bolt up the bracket on the tail pipe, ensuring that the bracket, if fitted, will attach without pulling on the pipe, by shimming or slotting the mounting hole. Then attach the silencer, again making sure that it doesn’t stress the pipe in any way.
I’d first check the flange is not deformed if you haven’t already. Place a straight edge across all directions and use a feeler gauge to see how deformed it is at all locations as follows:
Horizontal centre (ie through bolt holes)
vertical right near mounting bolt
vertical centre of RH pipe cutout
vertical centre of LH pipe cutout
vertical left near mounting bolt
If any of these are more than a few thou out you need to flatten the mount surface by tickling on a mill, grinding, or filing until it is flat. Just like carb mount faces when you mount it do not overtighted the nuts as this distrorts the flange too. You often find it is bowed in near the bolt holes due to past overtightening onto soft gaskets. Sometimes just backing them off a little can improve sealing.
There is also the steam engine method of sealing, and just let it seep as eventually it will likely clog itself up!