this motor is a little hard to start but runs very well at once it gets pass about 2000 rpm , it goes dead sometimes when i apply more throttle. Also 0nce it i run it for 20 minutes or so to get to the destination and stop for 20 minutes or so it is hard to get started again. the carbs have be cleaned and the compression is 142 psi + or - 4 psi . the timing is correct and the idle speed in neutral is 900 rpm ,,, can you folks help