Hi I've had my Cota for 6 months or so its a 1976 247T and it has had a habit of the exhaust flange coming loose. I eventually discovered the thread in the barrel is crossed and worn and the flange simply won't hold. I removed the flange washer in order to try and get the manifold in another quarter inch and used Loctite Blue Max and this appeared to hold for the first ride but another 2 hour session and the whole thing is loose again.

I am not sure what my options are as I have never encountered this type of problem before.

Look for a small hole in the top cooling fin above the exhaust port. install a stiff spring between there and the flange nut so if it undoes it works against the spring. Mine all have the hole, I don't know if it's stock or a common mod....

The hole in the fin and holes around that flange thing that screws into the barrel are all stock. One thing I did find useful to lock things up was to really give the flange and the barrel a really good clean with thinners or similar, smother the threads with silastic, put that spring Vintage Cota described and let it cure for about 24 hours. That silastic is fantastic stuff and will withstand temps of up to 500 degrees. Cheaper than getting the thread on that barrel done

Well there are no holes in my fins and no spring shows on any of the parts diagrams for the 247 that I have. I have wired it up before but that doesn't work as the thread just gives.

I have refitted with Permatex Black silicon and I will have a go at drilling and hooking up the spring.