You may or may not need to remove some body panels for this job. You might need a flashlight and something soft to kneel down or lay on, as well as a set of sockets and wrenches, a Phillips screwdriver, a set of feeler gauges and a pair of pliers.
NOTE: THIS SHOULD BE DONE ON A COLD ENGINE!!!
1. Place the scooter on the center stand.
2. Remove the breather pipe from the valve cover.
3. Remove the valve cover from the engine. There is no need to drain the oil. Some engines will have a metal tube that's in the way. Remove the two bolts holding the tube to the head and the valve cover/tube will come off as a unit. Immediately wipe off the oil that runs out of the top of the cylinder head so it doesn't run into the cooling shroud.
4. Remove the cooling fan shroud from the right side of the engine to expose the flywheel. There is a 1 inch diameter access plug in the fan shroud for timing mark viewing with a flashlight, however it's better to remove the entire cover to familiarize yourself with the marks if it is the first time you are performing this task.
5. Turn the engine to line up the T mark on the flywheel with the alignment mark on the engine case as shown below. This places the piston at the top of it's stroke and assures the valves are closed. Ignore the F mark.
IMPORTANT! At no time during the adjusting process should you allow the flywheel to move!
The three cam sprocket holes should be aligned as shown below. If the T mark is aligned but the holes on the cam sprocket are not, rotate the flywheel 360° (1 full turn) and then it should line up correctly. Both valves are adjusted with the cam in this position.
6. Loosen the 9mm lock nut on the adjuster and using a gauge placed in the gap, turn the adjuster screw until the gauge is snug but not tight in the gap as shown in the following pics. The manual says .05mm for both valves. That's about .002 - .003 in. It helps to bend the tip of the gauge to get into tight places.
7. Now the tricky part. Tighten the locknut without allowing the adjuster screw to move. This usually requires holding it with a pair of needle nosed pliers or some other tool while tightening the lock nut with a wrench, and may require a couple or more attempts to get it just right. Leaving the gauge in the gap while tightening the locknut is helpful. Again, you want the gauge to be snug but not tight in the gap after the locknut is tightened.
Tighten the locknut very tight. Don't strip the threads, but the last thing you want is for it to loosen up on you 35 miles from home. If you hear a loud tapping when the engine is idling, then the gaps are too big.
8. Repeat the process on the other valve.
9. Replace the valve cover and tighten the bolts in a criss-cross pattern.
There is no need for a new gasket.
10. Re-attach the breather pipe to the valve cover.
11. Replace the fan shroud.
12. Re-adjust the idle mixture screw according to this guide:
http://www.scooterforumonline.com/index.php/topic,1603.msg7405.html#msg740513. You are done!
Final Note: Once you are familiar with the marks on the engine and the cam sprocket you don't ever have to remove the fan cover in the future to adjust them. You can use a socket on the center plastic hex hub on the fan right through the center of the fan cover to rotate the engine till the cam holes are aligned at the right position. Just make sure to use the right size socket so you don't round off the plastic. It's a 13 or 14mm I think. You only have to remove the fan cover if you are going to install a new cam or remove the top end so you can align the cam properly.
