Yeah I`d think welding would be a good idea while its apart, and perhaps even more so now that its slipped once..not sure if this makes sence, but it seams like it could slip again a bit more easily once its done it once?
as far as which one is off..I`m not sure which would be most likely to be off, but I`m thinking that if which ever one is off, is off enough, you may be able to see it...
its been a while since i had my crank out (its an 800, but still) I`m pretty sure, that when you put the dots at the 12 o clock position, that the pistons should be even..even meaning, number 1 at TDC, and 3 & 4 even..or, which ever way it works out..they should be even one way or another..
hope that made sence?
say for example, the dot on the big gear, was at the 12 o clock position, yet, the piston was just a tad down..that would likely indicate that the large gear was off..same with the small gear..if it was at the 12 o clock position, yet the 3 & 4 pistons were`nt lined up..that would indicate that the small gear was off...
thing is..i can`t remember exactly which pistons would be even, and which would e at TDC...but it should`nt be hard to figure out, once you line up the dots, then position them at 12 o clock..two pistons should be a bit off...(if its defiantly twisted)..but if its only off by a couple degree, it may be very difficult to detect?