What is the method for adjusting motorcycle valve clearance?
4 Answers
Motorcycle valve clearance adjustment method is as follows: 1. Adjustment for overhead camshaft valves: Remove the magneto cover and valve chamber cover, rotate the magneto rotor counterclockwise to align the "T" mark on its outer circumference with the mark on the engine casing. At this point, the piston should be at top dead center of the compression stroke. Then select a feeler gauge of specified thickness, insert it into the valve clearance and pull it back and forth. If slight resistance is felt, the clearance is appropriate. If there's no resistance, adjustment is needed. First use a small wrench to turn the adjustment screw while pulling the feeler gauge to sense resistance. Once the clearance is correct, tighten the adjustment nut. 2. Adjustment for side valve clearance: Side valve clearance refers to the gap between the valve stem end and the adjusting screw on the tappet. Remove the valve chamber cover and spark plug, then block the spark plug hole with your finger while stepping on the kick starter. When airflow impact is felt, the piston is in compression stroke. Insert a screwdriver into the spark plug hole and slowly step on the kick starter. When the screwdriver reaches its highest point, the piston is at top dead center. Then check and adjust the valve clearance using the same method as for overhead camshaft valve clearance inspection and adjustment.
Last time I helped a friend adjust the valve clearance on his motorcycle, I first made sure the engine was completely cooled, because when hot, the gaps become larger and inaccurate. Locate the valve cover on the engine—usually at the top—remove the cover with a wrench, and use a feeler gauge to measure the clearance. If it's too tight, the engine will make a clicking sound; if too loose, it may cause air leaks and affect performance. Adjust the screw bit by bit: loosen the lock nut, slightly turn the adjusting screw to set the clearance to the manual's standard value (check your bike's manual, don't guess), then tighten the nut. After reassembling the cover, test-start the engine to listen for smooth operation. The job isn't hard, but don't rush to finish and hit the road—I recommend checking it at least every 10,000 km to prevent engine wear and extend its lifespan. After riding for so many years, maintaining this habit has kept my motorcycle running smoother with fewer repairs.
I've adjusted the valve clearance on my motorcycle several times myself, and it's been incredibly fun. Prepare the necessary tools: feeler gauge, adjustable wrench, and a rag. Make sure the motorcycle is completely cooled down before starting, as doing it hot is risky. After removing the valve cover, directly measure the gap with the feeler gauge—if it doesn't fit or is too loose, adjustments are needed. Slowly turn the adjusting screw until it just meets the standard value (which varies by model, so check the manual), then tighten the lock nut to prevent loosening. The whole process takes about ten minutes—don't apply too much force and damage the parts. After adjustment, the engine runs much smoother with improved power. Regular maintenance like this saves a lot on repair costs; checking every 5,000 kilometers or six months is safest.
Adjusting valve clearance is quite straightforward. First, let the motorcycle cool down for a few hours. Locate the engine valve cover and remove it using a wrench. Then, use a feeler gauge to measure the clearance: it should slide in with slight resistance for proper adjustment. If the clearance is incorrect, loosen the lock nut, fine-tune the adjusting screw to the correct position, and then tighten the nut. Finally, reinstall the cover, start the engine, and listen for any unusual sounds. The whole process takes about 15 minutes—beginners should take their time and stay calm. Remember to follow the clearance values specified in the manual, as incorrect adjustments may damage the engine.
