i have a 99 sportsman 500 it starts and runs to about 1/4 throttle then any further it starts poppin back through the carb and wont rev up any more it is getting to much fuel i think or isnt burning it i have rebuilt carb adjusted the floats and the jet needle i even put new spark plug and boot and cleaned the pickup coil so it will have good spark please help thanks

Could be the needle jet is worn allowing too much gas through. You could lift the "C" clip a notch or two and try that or go with a smaller main jet....

thanks i tryed that with the c clip and in helped but doesent have any power still

If it's down on power that could be due to worn lobs on the camshaft. This was a common problem on the pre-2001 500 Sportsman models....

It could be worn cam lobes, a plugged exhaust, a torn carb diaphragm, or a torn boot between the carb & cylinder, as well as a carb needing an adjustment.

i checked spark plug again and it looks like maybe the exciter coil is goin out do yall think that could be the problem

Could be going out or could be out of adjustment. An out of time situation, or a weak/intermittent spark can also cause problems.

When an engine starts popping through the carb it is often because the intake valve clearance is gone.

Loss of power can also be caused by incorrect valve clearance.

If all else fails have a look in that department.