I'm having fits out of my son's 2007 KFX 90. It will not start without taking my hand and blocking the air intake. After it starts and runs for a few minutes, it runs fine and will start easily. I've spent alot of time reading other threads and was convinced that it was the electric choke. Paid $93 and replaced it with an OEM choke. Suprise, same problem. I've also read where the carb should be replaced with an aftermarket carb with a manual choke. That would have been a cheaper route, but I would prefer to keep it as close to stock as possible. Could it be an issue with one of the carb jets? At one time, it started great so I'm just not sure what the issue could be. It's a great quad, I just need to get past this one major issue. I'm gonna wear out the screws that hold the top of the air box on! Any help would be greatly appreciated.