A buddy of mine has a f4i i am thinking about buying it for a stunt bike. The only thing wrong with it is when you put it in, i can't remeber if it is second or third, you put it into gear and the revs hit about 6grand and it pops out of gear into like a neutral. Only does it in one gear.

 

TTT

I have the same prob. Just recently, it happens to me in third. Don't know what caused it. Nothing comes to mind how it happened.

I'm in third hard on the gas and it will jam back down into 2nd. All of the other gears are fine.

I don't know what the hell is wrong with it...

 

the problem is the detent arm, and gear selector drum or " shift star". the stock one is a piece of crap.
factory racing makes a way better detent arm kit and shift star.
i have this kit on my bike and it work flawlessly. shifts are way faster and it never pops out of gear. both kits are about $200 bucks but well worth it.