If you ride a motorcycle sooner or later you're going to deal with your bike's scheduled valve adjustment. Many people are quite happy to drop off their bike at the local shop and pay a mechanic to perform this task. But with a few simple tools and some basic mechanical skills you can accomplish this job yourself. If you do you'll save money and time as well as improving your mechanical ability, all while increasing your knowledge of your bike's inner workings.
If you're ready to take the plunge and tackle the job read on, because that's just what we did with our long-term 1996 Yamaha Virago 1100. This particular bike's get-up-and-go had got-up-and-went, and we felt it was time to bring the valves back into the swing of things. After clearing a space in our cluttered shop, we tossed the beast up on its center stand, put on our rubber gloves and went to work.
Valve clearances must be checked on a cold engine to ensure proper readings. Your next step is to remove all parts that limit your access to the valve cover. Our Yamaha manual recommended removing side covers, seat, airbox, spark plugs, and fuel tank. However, we found that removing the tank was more trouble then it was worth due to its sub tank and marathon-length plumbing. Instead we unbolted the tank and propped its rear up about two inches which allowed sufficient maneuvering room. Obviously the amount of parts you must remove will depend on which motorcycle you are working on. Sportbike riders will be forced to remove fairings and probably radiators, while BMW boxer-twin riders are just laughing at us all right now.
Next, the left-side ignition cover must come off to reveal a 22mm nut at the crankshaft's end. On the Virago you'll find a sight window above this nut which is used to align the timing marks. Turn the crankshaft with a 22mm socket until a "T" appears in the sight window, indicating top dead center (TDC) for the rear cylinder. Check the rocker arms for free play. If they're tight, rotate the crankshaft another 360 degrees and check the rocker arms again. When they have free play, check the clearance between valve stem and rocker arm on the exhaust valve. If it's out of spec, loosen the 12mm lock nut and use a 4mm Allen® wrench to turn the adjuster screw. Hold the adjuster screw in place while tightening the locknut then recheck clearance with your feeler gauge. Repeat this process for the intake valve. It may take a few tries to get it right, so be patient -- you want your bike to run at its prime, don't you?
Now rotate the crankshaft clockwise until the "I" mark lines up in the window, which on the Virago indicates TDC of the front cylinder. Check for rocker arm free play and adjust clearances if necessary, as with the rear cylinder.
Valve adjustment procedures are fairly similar from bike to bike, and lessons learned here can be applied across a broad spectrum of motorcycles. A factory service manual is very useful, as is having all the necessary tools at hand. Be sure to work on your bike's engine when it is cold, and wear gloves to help keep oil off your paws. If all goes well, give yourself a pat on the back and reward yourself by buying those new gloves you've been eyeing with the money you just saved!
Required tools: Feeler gauges Hex sockets: 13/16, spark plug, 10,12,17, & 22mm Allen® keys: 4 & 5mm