Motorcycle Repair: CT-90 Valve timing, flywheel alignment, punch mark

Question
How do I set the valve timing on a 1970 CT-90?  I recently purchased a new piston and rings for it, and after disassembly, my kids turned the crank...

Answer
Paul,  turn the crankshaft to the T mark on the flywheel alignment.

Look at the camsprocket. It should have a round O punch mark one one side.

Look at the opening on the cylinder head. There should be a notch or mark on the head, as I recall.

The camshaft inserts with the lobes down towards the crankshaft (compression stroke). The camsprocket goes into the camchain and then the alignment with the punch mark on the cam and the mark on the cylinder head should match, when the piston is at TDC (T mark).

Basically, as you look at the layout, there is a straight line between the center of the crankshaft, through the camshaft mounting bolts to the cylinder head..

head< ( O<>O )cam sprocket (or 90 deg to this) O crankshaft (set at T alignment).

Hope that is clear enough for you. When the piston is at TDC, the valves are both closed. When you turn it over one turn the valves will both be slightly open at the T mark alignment (overlap stroke).

Turn it over slowly after you have installed the bolts. If it starts to get tight/hitting something DO NOT FORCE IT!
Recheck the valve timing again.

Bill Silver