Welcome to the world of flame gulpers
Fun isn't it
Looks tight 
?
That's where the timing has slipped, needs a locking nut or a spacer made so the screw can locate down onto the rear valve opener, I think I'll be remaking the cylinder and piston as it looks to have rusted up over the last two days. It can't stay like that indefinitely. So I've found a company that sells short lengths of graphite rod quite reasonably