Originally called the XS1 when introduced to North America in 1970, the Yamaha XS650 was a Japanese copy of British parallel twin-cylinder motorcycles such as the Triumph Bonneville and BSA Lightning. Known for reliability and ease of maintenance, the XS650 lacked some of the style of its British counterparts but made up for it in performance. To properly adjust the valves on the XS650, the cam chain must be adjusted prior to the valves. The XS650 valves can be adjusted on a cold engine, which eliminates the danger and difficulty of working on a hot engine.
Things You'll Need
- 3/8-inch drive socket wrench
- Metric socket set
- Metric wrench set
- Small metric crescent wrenches (optional)
- Feeler gauge
Remove both spark plugs with a socket wrench and spark plug socket. Shift the transmission into first gear. Place the motorcycle on its center stand.
Use a wrench (preferably a crescent wrench) to remove the cap located behind the cylinders, underneath the carburetors. Inside the hole is a threaded stud with a lock nut on the end. Inside the stud is a small pin, which should be even with the end of the stud. If it is not flush, it needs to be adjusted.
Rotate the rear wheel forward. While rotating the tire, the pin should move in and out an equal distance in both directions. Stop turning the tire when the pin is in the middle of its stroke. Loosen the lock nut with a wrench and turn the stud until the end is even with the end of the pin. Tighten the lock nut and replace the cap. The cam chain is now adjusted.
Look into one of the spark plug holes using a flashlight. Turn the rear wheel until the top of the piston is visible in the spark plug hole. The engine is now at top dead center.
Remove the valve covers using a crescent wrench. Four valve covers are located on the front and back of the two cylinders; three are round and the left front cover is square. The exhaust valves are at the front of the cylinder and the intake valves are at the back.
Adjust the valves on the cylinder at the top of its compression stroke, which is the one with the closed exhaust valve. Insert a feeler gauge of the correct thickness between the rocker-arm bolt and the top of the valve stem. The clearance is correct when the next size up feeler gauge will not fit in between. Adjust using a crescent wrench by turning the bolt on the top of the rocker arm counterclockwise to tighten or clockwise to loosen. Bring the other cylinder to the top of its compression stroke and repeat. Remount the four valve covers.
Tips & Warnings
- According to 650 Central, the valve clearance specifications for the Yamaha XS650 are: 1970 to 1972 models, intake valve .003, exhaust .006; 1973 to 1975 models, intake .003, exhaust .004; 1976 and 1977, intake .002, exhaust .006; 1978 models, intake .004, exhaust .006; and 1979 to 1983 models, intake .0024, exhaust .006. Measurements are in thousandths of an inch.
- Photo Credit Jupiterimages/BananaStock/Getty Images
How to Adjust Valves
Drag racers who compete in sanctioned events around the country must be able to produce a vehicle that has reliable performance in...
How to Troubleshoot Ford Superduty Brake Light Problems
Brake-light problems on the Ford Super Duty are caused by one of a few issues. A faulty fuse, faulty wiring at the...
How to Adjust the Cam Chain on a Yamaha XS1100
The Yamaha XS1100 was produced from 1978 to 1984 and was Japan's first "super bike". Its four-cylinder, dual-overhead-cam engine propelled the XS1100...
How to Adjust the Clutch on a Yamaha 650
The clutch on your Yamaha 650 motorcycle allows you to effectively cut the power that drives the rear wheel. Doing so allows...
How to Adjust a Turbo XS Blow Off Valve
A Blow Off valve, or BOV, is a component found in most turbocharged engines. It is used to release compressed air from...
How to Wire a Yamaha XS650
The Yamaha XS650, a motorcycle made from 1968 to 1985, must be properly wired before it can be used. Though wiring can...
How to Set the Pilot Screw on a 1983 Yamaha Maxim 650
Your Yamaha Maxim 650's carburetors rely on a quartet of pilot screws to meter the amount of air and fuel allowed into...
How to Adjust the Valves on a 2001 Yamaha Kodiak
The gap between your 2001 Yamaha Kodiak's valves and the rocker arms that move them is called valve clearance. This gap is...
How to Clean the Carbs on a 1982 Yamaha Maxim 650
The effects of time can take a toll on a motorcycle, especially if it has been stored without regular maintenance. While there...
Yamaha XS650 History
Yamaha's XS650 was introduced in 1970 as a powerful alternative to the British motorcycles that had been ruling the streets from the...
Yamaha Xs650 1979 Electric Starter Troubleshooting
The Yamaha XS650 is a popular line of motorcycles produced in the 1970s and early 1980s. Even today, they are still popular...