I had my 250 started - can't get it running today

[rgnprof]

I finally got everything back together on my '72 250 and I had it running yesterday. Hard to start and a lot of carb backfire, but once I got it running and good and warm it ran fine. Tried to make some adjustments and I think I made things worse because today I couldn't keep it running.

Yesterday, I had some carb sync problems and I had fuel dripping from the rear carb at idle - tried to make the necessary adjustments, but now I'm stuck. Double checked my Crane and it seems fine and I have fiddled with the timing all afternoon to try and get it running. I did get it started a couple of times today, but serious carb backfire - were talking some flames here! And I couldn't get it to idle. I'm not a Zenith novice as I have fine tuned these things several times over the years. I just can't get it started this time. I'm sure redoing all of the engine stuff, new timing chain, a valve job etc. has affected everything and I'm almost certain the chokes are messed up, the timing is probably off (although I did check it and it seemed fine) and the carbs are seriously out of sync - I guess I just don't for sure where to start - especially if I can't get it running.

Any advice?

ryan