In this world, people get paid for results - not time spent trying. A certified BMW tech with a diagnostic computer should have no problem figuring out a no start problem. Are the plugs sparking when the engine is turning over? does it have compression? if yes and yes, it's a fuel issue. It just isn't that fucking complicated, this is clear cut incompetance.
If I read the op's last post he still owes part of the bill? for cripes sake don't pay any more. If you paid by check or cash just forget it and move on. If you paid by credit/debit card I almost guarantee a victorious dispute. Say the only reason you paid is because they wouldn't let you have the bike back after an unsuccessful attempt to fix your bike. I've disputed bad service before and won - write up a detailed report with any emails, they will have to prove they earned your money - how could they possibly do that?