Disconnect the cable from the negative terminal of the battery, remove the air filter housing, raise the vehicle and support it securely on jackstands, and drain the engine oil. Disconnect the exhaust pipe at the exhaust manifold and remove the structural collar. For 4WD models, support the front axle assembly with a floor jack, remove the front axle assembly mounting bolts, and lower the axle housing as much as possible. Remove nuts from the engine mounts, support the engine from above with an engine hoist (avoiding the intake manifold), take the weight off the engine mounts, and remove the engine mount through-bolts. Raise the engine sufficiently to allow access for oil pan removal, then remove the mounting bolts and lower the oil pan using a criss-cross pattern to loosen and remove the bolts. If the pan is stuck, tap it with a soft-face hammer or use a wood block to assist. Remove the oil pump pickup tube and screen assembly, clean both thoroughly, and install with a new seal. Clean the oil pan and sealing surfaces on the block and pan, removing all traces of old gasket material, and check for distortion, straightening or replacing as necessary. Apply a 1/8-inch bead of ATV sealant at the cylinder block-to-oil pump assembly joint at the oil pan flange and install a new oil pan gasket. Place the oil pan into position and install the bolts finger-tight, then tighten them to the specified torque. Lower the engine and install the through-bolts in the engine mounts, tightening them securely. Install the structural collar by placing it in position between the transmission and the oil pan, hand-starting the collar-to-transmission bolts, hand-tightening the collar-to-oil pan bolts, and then tightening both sets of bolts. The remainder of the installation follows the reverse order of removal. Refill the crankcase with the correct quantity and grade of oil, run the engine, and check for leaks, followed by a road test to check for leaks again.