Did you try JB Weld for plastics? On the plastics I’ve repaired this stuff has worked well. Proper preparation of the surface material to be repaired was key.
https://www.jbweld.com/product/plasticweld-syringe
Where is it leaking? Can you make a large patch of similar material and use the sealant to attach it over the leak?
Have had luck with this on plastic Polari RZR fuel tanks.
I tried it on a 5 gallon plastic gas can and it ate right through the stuff. But maybe I got a bad batch.
Check out a kayak dealer. They do plastic repairs, and if the tank is similar to the weld "rod" they have, it can definitely be fixed.
It has 2 brass nuts molded into the plastic. Bolts into those nuts and a bracket is how the tank attaches to the backbone of the motorcycle. Not sure if its leaking through the nuts or around the nuts. I used some thread sealant on the bolts but they still leaked.
Called OKC kayak. They do all plastic repair in house. Told me they would be happy to look at the tank and try to repair it. Thanks for the recommendation!
