Trying to remove the axle to replace bearings.
Pull off. After you've tried all of TXm42's suggestions, soak it with penetrating lube. Turn off the petcock and drain the carburetor - so you don't make a mess on the floor. Flip the quad on it's right side (with the left wheels facing up). Spray the splines with penetrating lube (available at auto parts stores) and let it sit overnight. Then repeat TXm42's ideas.
They are splined and mate with a spline on the axle. It has a big nut that retains it. Remove that nut,,,and the sprocket carrier/hub just slides off the axle towards the left. It just Slides Off. Ya,Right,,,famous last words :) The $#% 'd things are Very Tight to begin with,,,and seem to grow Roots over time. You'll probably have to Beat the thing off,,using care not to damage anything. Penetrating oil helps. USUALLY a 16oz Hammer is almost pointless,,,you need a Big Hammer 2-3 pounder at least Or,,,Heat and Beat Or,,, Use a Puller,,,,I should say,,Rig up a Puller to Use Be very cautious of YOUR personal safety. Or,,remove the whole assembly and use a Hydraulic Press. Many Auto Parts places can do the Pressing for You,,,most any bike shop,,,lots of Auto shops,,or automotive machine shops. The cost is typically very low. Once you get it all apart,,,Clean ALL the splines very thoroughly,,,and reassemble using an actual ANTI-SEIZE COMPOUND. Good hi-grade wheel bearing grease is usually good enough,,,but not the 1st / Best choice Good Luck,,,it may come off easy for you,,,,many times it can be a Tuff Chore. If it's obviously gonna fight back and be Really Stubborn,,, You'll probably come out ahead to take it to somewhere that can press it off. Fighting things like that too often ends in Damage or Injury.
I would hope that the sprocket doesn't spin off. Usually, you would expect the sprocket to be fixed to the rear wheel, usually by a series of bolts. Front sprockets are often on splined shafts held in place with a nut and tab washer.
