|Finding TDC/Adjusting Valves
Finding TDC (top dead center) and turning the engine over for the purposes of adjusting valves can be a pain in the ass. Here is an alternative to using the rear wheel for turning the engine and looking for the timing marks on the flywheel.
Remove the alternator cover and both valve covers. Use a 15/16" wrench/socket on the alternator nut--this will turn the engine over. Turn the engine over in the normal direction of rotation (if you’re not sure which direction that is--take the wrench off and just tap the starter button to see). Watch the rocker arms on the cylinder that you will be adjusting the valves on. You will see them move up/down as you turn the engine over. You are trying to find the point at which BOTH rocker arms move (the intake valve is just starting to open and the exhaust valve is almost closed). This is called "valve overlap" and it is the position in which the piston is at TDC with both valves slightly open for that cylinder. Take a marker/pencil and place witness marks on the alternator rotor and the engine case--label this mark for the right or left cylinder (the one you are adjusting the valves on). Now rotate the engine (same direction as before) ONE complete turn, lining up the marks you just made. The piston for that cylinder is now on TDC, compression stroke--both intake and exhaust valves closed. Adjust the valve clearance for that cylinder.
Repeat the same process for the other cylinder. This procedure will work on any four-stroke engine regardless of the number of cylinders. For any skeptics in the audience you can use a soda straw and place it in the spark plug hole to make sure the piston is really at TDC or look at the timing marks on the flywheel. Also when you reinstall the alternator cover use four lock washers on the screws as they tend to come loose.
[note: an easy way to find TDC on compression stroke is to feel for compression in the spark plug hole as you’re turning the engine over by hand. You’ve now found the compression stroke. Stick a clean screwdriver/stick/straw/whatever in the hole and watch as the piston reaches the top of its stroke. You’ve now found TDC on the compression stroke- ed the ed.]