Sounds like timing to me. BUT,stranger things have happened. When I installed an H.E.I. system to my 261,it wouldn't start,either.(Ran GREAT when parked)! After about two weeks of frustration,I found that my carburetor float needed adjustment,Then it would only start and run after the carb. was primed. I replaced the fuel line from the tank to the fuel pump,and the fuel pump,(hardly a dribble,at the carb.)I also installed a filter between the tank and pump,and another at the carb. It ran,but not like it should,after that.(sluggish acceleration,and sputtered out the exhaust-No backfire). Then I replaced the carb,because i found the base was warped,causing a vacuum leak. After a month of chasing a dozen "gremlins",It finally runs better than ever,thanks to the HEI. Just take one thing at a time,like these GREAT folks suggest,and you'll be up-and-running in no time!
