Things You'll Need
10 mm socket
Spark plug socket
6 mm Allen wrench
17 mm socket
Blade-type feeler gauges
12 mm socket
5 mm Allen wrench
Magnetic pickup tool
Kawasaki's KFX400 was a sport all-terrain vehicle produced from 2003 to 2006. Curiously, the KFX400 was co-developed by Suzuki, which led to the production of the nearly identical LT-Z400. Both models require a strict maintenance program to ensure the ATV operates at its peak level of operation. This includes a routine inspection and adjustment of the air gap, or clearance, between the intake and exhaust camshafts and their corresponding valves every six months. The valves are operated by a pair of shimmed tappets that can be removed to keep the valve clearance within a specified range.
Park the ATV on a level work surface and allow the engine to cool for a minimum of four hours.
Remove the seat from the ATV using the release lever under the rear fender. Unscrew the gas cap, then remove the pop rivets from the base of the upper fuel tank cover and both side covers using the tip of a Phillips screwdriver. Pull the upper and side covers away from the ATV. Screw the gas cap into place.
Turn the fuel valve lever under the left side of the gas tank to the on position. Pull the fuel hoses off of the fuel valve, using pliers. Remove the bolts from the base of the gas tank using a 10 mm socket and a socket wrench. Lift the base of the tank upward, then pull the tank away from the ATV's frame.
Unplug the spark plug cable from the top of the engine cylinder head cover, then unscrew the spark plug using a spark plug socket. Pull the oil hose and breather hose off of the top of the cylinder head cover. Remove all three bolts securing the cylinder head cover to the cylinder using a 6 mm Allen wrench.
Remove the generator port cap, located at the center of the left engine cover, and the timing port cap, located just above the generator cover cap, using a 6 mm Allen wrench. Place a 17 mm socket and a socket wrench on the end of the crankshaft, located within the generator port.
Rotate the crankshaft clockwise until a T-shaped mark is aligned with the triangle printed into the left engine cover below the timing port. The pointed portion of the intake and exhaust cams, located at the top, left side of the engine cylinder, should be pointing away from each other and toward the front and rear of the ATV. Rotate the crankshaft clockwise 360 degrees and realign the T mark with the timing triangle if the cams are pointing inward, toward each other.
Measure the clearance between the valve tappets and the exhaust and intake cams, located at the front and rear of the engine cylinder, using a blade-type feeler gauge. Ideally, there will be a 0.0039- to 0.0071-inch gap between the intake cam and tappet and 0.0079- to 0.0118-inch gap between the exhaust cam and tappet. The tappet shims must be replaced if either exhaust or intake clearance is out of specification.
Unscrew the cam chain tensioner spring holder bolt and spring, located at the rear of the engine cylinder, using a 12 mm socket. Remove the cam chain tensioner mounting bolts using a 5 mm Allen wrench.
Take note of the direction the cams are pointing, then remove the camshaft holders using a 10 mm socket. Lift the camshafts off of the engine cylinder head to access the intake and exhaust tappet shims. Place a screwdriver under the center portion of the cam chain, located at the top of the engine cylinder head, to keep the chain from falling into the engine.
Remove the shim from the top of the intake or exhaust valve tappet, if the valve clearance is not within the valve's specified range, using a magnetic pickup tool. Take note of the number imprinted into the bottom of the tappet shim, which indicates the shim's thickness in millimeters. For example: A shim with the number 280 indicates a thickness of 0.11 inch. Select a thinner shim if the intake valve clearance is less than 0.0039 inch. Select a thicker shim if the valve clearance is greater than 0.0071 inch. Coat the top and bottom of the new shim with a molybdenum-based grease, then slide the shim onto the top of the tappet.
Reinstall the camshafts onto the engine cylinder head, pointing the cams away from each other in the same position they were removed. Reinstall the camshaft holders, then tighten the holder bolts to 7 foot-pounds using a torque wrench.
Push the release latch, located on the inner tip of the tensioner, into the cam chain tensioner body. Push the tensioner push rod into the chain tensioner body, then mount the tensioner onto the engine cylinder. Screw the chain tensioner mounting bolts into place and tighten the bolts to 7 foot-pounds. Push the tensioner spring into the tensioner body, then screw the spring holder bolt into place. Tighten the spring holder bolt to 21.5 foot-pounds.
Turn the crankshaft two complete turns to seat the shim, then realign the T mark with the triangle at the bottom of the timing port. Recheck the valve clearance. Replace the shim with a thinner or thicker shim, if needed to bring the intake valve clearance between 0.0039 to 0.0071 inch or the exhaust valve clearance between 0.0079 to 0.0118 inch.
Reinstall the engine cylinder head cover. Tighten all three bolts to 7 foot-pounds, then tighten the bolts again to 10 foot-pounds. Push the oil and breather hoses into place, then screw the spark plug into the center of the engine cylinder head. Tighten the spark plug to 8 foot-pounds, then push the spark plug cable into place.
Reinstall the gas tank, then push the fuel hose onto the fuel valve. Reinstall the upper and side covers onto the ATV. Reinstall the seat.