i have no idea whats goin on with it. it gets fuel all the way to the carb, i also pulled the carb off and the float looked fine, no gunk anywhere, it gets air because i ran it without the air filter for just revving it. there is also a knock in the engine, im thinking its the timing chain. it may be stretched. i just need some help and any ideas without having to rip the whole engine apart

 

Your carb is getting fuel, but it could be either too much or not enough and it could cause the engine to bog/hesitate. Read/inspect your spark plug color to determine that. A loose cam chain normally causes more like metallic rattling noise from top end. Also, your 250 has an automatic cam chain tensioner that pushes against the chain guide and takes up any slack in the chain that may exist. But if you really think it is the chain, check to see if the tensioner is maxed out (extended all the way in) or something wrong with it. If maxed out, then the chain needs replacement. I've seen sometimes that tensioner stopped in the middle and would not push in anymore. By the way, the chain does not really stretch but it gets worn out - giving the same impression/result - longer in length. The real cause is the poorly maintained air filter allowing dirt to enter into the engine and/or dirty engine oil. Check the cylinder compression which should be 150+ psi with elec start when cranking at about 400~500 rpm and maybe a leak down test. Good compression usually means your top end is OK.

 

check your idle adjustment screw..

WE just rebuilt the carb on my friends bayou 220..
ran great, than a few days later after a ride.. she could start, but any throttle killed her.
One twist of the screw to lean her out, and she purred like a kitten all day

 

Idle adjustment screw does not the change carburetion setting, neither leaner or richer. Idle adjustment only changes the engine idle rpm. The air screw changes the Fuel/Air ratio. You turn OUT to make it lean (more air), and turn IN to make it rich (less air) - the spec is 1.5 turn out on 250 after you softly bottom out first. The idle adjustment screw on the carb is pointing horizontally toward left side of the atv. The air screw is pointing vertically down toward the ground. These two can be easily mixed up on this atv.