This pulsar your talking about, could it be that youre referring to the fuel pump? If so, this would be something to check...usually they are vacuum controlled by a hose to the crankcase...if the hose is leaking then the fuel pump wont work or work crappy. Also check/replace the fuel lines for leaks, Ive had sets that looked fine that had no holes but made the motor run bad if it would start at all. I dont know why, but replacing them solved the problem.
One other thing, I know its a long shot but...check your spark. I have a 77 Yamaha YZ80 that was getting gas and everything, but it would only run on starting fluid. Turned out the coil and stator were both junk and would only produce barely enough spark to ignite the starting fluid. Replaced them and it made a world of difference. Just some things to check.
-Nick
1988 Chevy Silverado 5.9L Cummins : 1986 ATC250R : 2012 Polaris RZR 570 :
98% of Americans say 'OH $#!T!!' before going into a ditch on an icy road. The other 2% are Alaskans, and they say 'Here, hold my beer and watch this!!'