A friend asked me to look over his carb since a mechanic had told him the jets he bought for his 2006 yfz450 weren't fitting the carb. I disassembled, cleaned, blew through the passages, and reassembled. The float height was set (8mm) and it was reinstalled. It began to overflow to it came off again and I switched the needle to another I had that measured the same as the one in there (14mm long). Air/Fuel screw was adjusted to 2 turns out as it was only 1/2 a turn out.. I decided to switch it because the original one looked like the wire that loops around to catch the tang was a bit mangled. I installed it again and now it was stuck in the opposite direction (bowl was empty). I blew a bit of air through the inlet and it came down and got stuck down (overflowed). I came off again, got a quick spray down again, and went back on. The bike still would not run so it came off yet again and we went back to the original needle and 1/2 a turn out on the A/For screw. It fired and ran fine up and down the street. He loaded it up and took it home.
Next day he texts me and says the bike is not starting again. He felt confident having watched me do the carb to go through it himself. He said it wouldn't idle and would only turn on with the gas lever depressed. Also, it would shut off when he pulled the clutch in to shift. After several tries, the bike finally fired after I asked him to test the TPS. He hooked up lights and went around the block and his lights went off as he got into 3rd gear. He got it home and it wouldn't start again. I'm not sure if this is an electrical or fuel issue. Any pointers on where to get started with this thing? He has a carb kit and water pump seal kit (water leaking from tube attached to underside of water pump) coming in and we're going to do that. He mentions the bike has burned through several aftermarket lights (LED, etc) but he replaced the stator and regulator/rectifier recently. The harness has a few taped off ends. We're thinking electrical, but not sure where to start diagnosing before throwing money at it.