You do need to learn how to do it, because it is something that you must monitor in order to maintain peak performance. You will need a valve lash adjusting tool. Part number 35-3461 from
http://www.motorcyclecarbs.com or just ask your local Yamaha dealer for an FJ1200 valve lash adjusting tool (aka bucket holder) Most folks agree that lash should be .004" to .006" (.101mm to .152mm) on the intake, and .006" to .008" (.152mm to .203mm) on the exhaust. You measure each cylinder with the tops of the lobes of the intake cam and the exhaust cam for that cylinder pointing 180° away from each other, NOT pointing up. You turn the cam lobes by turning the crankshaft with a wrench on the rotor nut back by the firewall. (remove spark plugs first!) There are a few components that set the lash. Just under the cam lobes are some little disks which are shims, situated and held in cups that cover the top of the valve. The cups are actually lash caps that hold the shims, and the shims come in different thicknesses. The shim thickness is usually etched on the underside of the disk and is expressed in millimeters . You change the shims to change the lash.
To begin, you will need to measure and record the lash at each valve, and right beside that, figure how much you need to adjust each one. It will simplify things later to take your measurments in millimeters, and most feeler gauges have both inches and millimeters etched on them. As you measure this, be sure to turn the lash cap cup so the little slot is positioned where you can pop out the shims later with a small screwdriver.
Beginning at cylinder 1 at athe firewall, make a list like this:
I1a E1a
I1b E1b
I2a E2a
I2b E2b
and so on...
For each valve where your lash is out of tolerance, you will need to remove the shim, and replace it with a shim of the right thickness to achieve proper valve lash. If you don't have a stockpile of lash shims, you will need to remove your existing shim and record the thickness in order calculate what shims you will need to order. You can get shims from any Yamaha dealer, but you may be able to swap some around so you don't have to buy as many. 2.15mm is about as thin as you will find. If you need thinner shims than that, you are probably in desparate need of a valve job.
Shims normally have their thickness etched onto their underside. It will have 275 or 2-75 or 2.75, but they all mean 2.75mm.
The lash adjusting tool is used to hold the lash cap cup down so you can rotate the cam lobe out of the way and pop out the shim.
To do this, rotate the crank until the valve needing adjustment is all the way open. Place the adjusting tool in between the outside wall of the cylinder head and the cam lobe and screw the little screw into the threaded hole on the valve cover gasket surface of the head to hold it into place. The goal is to keep the valve lash cap, or bucket depressed. You may have to slightly turn the cam away from the holder to get it to sit right on the bucket as you tighten the screw. Then turn the crank so the cam lobe moves away from the holder, and keep turning til you have enough clearance to pop out the shim.
