To adjust the needle valve that regulates the amount of air to fuel mixture for the engine, carefully screw the valve in until it cannot go any further. Do not over-tighten the valve to avoid damaging the needle. If your engine is not starting easily, the intake and exhaust valves need to be adjusted. Remove the hood and the housing over the valves, and then adjust the tightness of the valves using an appropriately sized wrench.
If tightening the needle valve that regulates the air to fuel mixture does not fix the problem, unscrew the valve until it is out about 1.25 inches and start the engine. Slowly unscrew the valve until the speed of the engine slows so you have somewhere to start the adjustment. When the engine is slowed, the mixture of air to fuel is too strong, so gradually tighten the valve until you hear the engine hit its best rotation speed.
When adjusting the intake and exhaust valves, power off the engine, open the hood and find the OHV exhaust valve at the front of the engine. Using a socket wrench, remove the four bolts around the valve cover. Under the engine, rotate the crankshaft to compress the valve spring. Use a Torx wrench and unscrew the Torx screw on the upper rocker arm nut. Insert a .004 feeler gauge between the valve spring and the pivot point of the arm, and then tighten the nut with a wrench until the feeler gauge does not easily move.
Hold the nut in place with a wrench while tightening the Torx screw to preserve the adjustment. Compress the exhaust valve spring by rotating the engine. Repeat the process with the intake valve. Replace the valve cover and the engine hood and test start the engine.