Having problems with my frst. built it back up last weekend, started it up last night and it runs great one minute then rubbish the next!

It sounds like the fuel isn't getting through, but then it does the next minute?

Could it be the fuels regulator or maybe a loose wire??

It's not been moved for 11 months could it be just sh*t in the tank???

Any help appreitiated???
Cheers
Darren