Believe it or not I like regular maintenance, generally it keeps me busy enough that I wont go off and try to modify something. My 73 Honda CL175 requires frequent maintenance, an example of which is adjusting the valve lash. This is setting the gap between the rocker arm and valve stem. There needs to be a slight gap here to allow for the valve to fully close throughout the operating temperature range of the engine. The metal will expand or contract as the motor heats up or cools down.
These are general steps for adjusting the valve lash on my Honda but these steps may be applicable to other vehicles, the general idea behind adjustable valve lash is simple.
First thing is to actually get to the lash adjusters. Its a 19mm wrench to remove the four plugs. Here is what the lash adjuster looks like close up. A small rod is threaded through the end of the rocker arm. The rod has the square end sticking up. The nut you see locks the threaded rod into position. Below that the top of the valve spring can be seen. The smaller circle inside that where the rod actually makes contact with the valve stem. Thats where the the lash is measured.
Before checking the lash the engine must be in a position where the valve being checked is not open. To do this the timing cover must be removed to look at the timing marks. With the side stand down oil will come out from behind this cover so make sure the bike is tilted away.
Now to check the lash. Having an angled gage is great for this because of the tight clearance. If it is within spec than just leave it alone. Otherwise loosen the lock nut then turn the square end of the small threaded rod. Tighten the rod to reduce the lash or loosen to increase the lash. Once the lash is within spec the lock nut must be tightened. Be sure to hold the square end when doing this, it will have the tendency to tighten with the lock nut. Things are small so it takes some practice. Be sure to re-check the lash after you are done.