Time For A Service

After retuning from Mt Gambier, my bike has done nearly 13000 kilometers and a major service was due. I do the servicing myself now, as it helps me learn about the bike and cuts down on cost. The major service on the GS500 involves the following

Big Stuff:
Check the valve clearances (replace the shims if needed)
Replace the oil and filter
Replace the spark plugs
Replace the air filter
Correctly torque nuts and bolts
Check the drive chain (adjust or replace if needed)
Check the battery (recharge or replace if needed)

Smaller Stuff:
Check and adjust the idle speed
Check the fuel hoses
Check the brake hoses, pads and fluid
Check the PAIR hoses
Check and adjust cable freeplay
Check wheel runout
Check and adjust steering head bearing freeplay
Front and rear suspension checks
Lubrication of cables and pivot points

Things like tyres, lights and controls should be checked far more regularly. Of the above list, I have never checked the valve clearances before. This is probably the most time consuming task, but also an important one. After taking off the fuel tank, detaching the throttle cables, removing the breather cover and finally removing the valve cover I revealed the cylinder head, as pictured above.

Most bikes have four valves per cylinder (two intake and two exhaust) but as my bike is old technology, it only has two per cylinder (one intake and one exhaust). The GS500 has two inline (side-by-side) cylinders, so four valves in total. The camshaft at the top of the picture (towards the front of the bike) links the two exhaust valves, and the one at the bottom links the two intake valves. The cam chain in the middle rotates the camshafts. The gap between the cam and the shim that the cam lobe presses down on should be between 0.03-0.08 mm for all four valves. My feeler gauge has 0.05, 0.06, 0.08 and 0.10 mm blades, and the result was as follows.

Left Intake: 0.05-0.06 mm
Right Intake: 0.00-0.05 mm
Left Exhaust: 0.08-0.10 mm
Right Exhaust: 0.06-0.08 mm

The right intake valve clearance is some value under 0.05 mm which is fine. No commonly available feeler gauge has blades less than 0.05 mm, so I'll assume it is okay. Of more concern is the left exhaust valve which is out of specification, but only just since I can't get the 0.10 mm blade through the gap. I'll leave it for now as I haven't got replacement shims anyway, but it's something I need to look at for the next minor service.