I don't know for sure if they can be repaired but don't think so. I was advised to buy new when my one went tits up last year. Just checked the usual suspects MSD, GGR, Burton, Matt Lewis, R&B etc and looks like the amal valve is discontinued? Didn't hear about that to be honest...

If it's true I wonder will everyone be moving on and going boost controller, bleed valve or air injectors?