Small Engines (Lawn Mowers, etc.): Timing on a Honda HR194, honda hr194, piston rings

Question
Dear Eric

I have an a self propelled 19" Honda HR 194 rotary mower with a 4 HP overhead valve Honda GXV120 engine rated at 118cc. It has been creating clouds of blue oil smoke every time I start it which after running it for 5 minutes subside. I have completely stripped it down, thinking that the piston rings or valve rails might be responsible. However, despite this being a relativley old mower I can find very little wear in the cylinder on the piston rings or around the valves or valve rails. Have you any idea what might cause this smoking? Furthermore having stripped it down I realise I was very stupid and didn't make any marks on the cam or crank shafts to indicate the timing. Are there any standard procedures for working out the timimg or should I simply resort to first principles?
Many thanks
Robin

Answer
To set the timing, turn the crankshaft until the piston is as the top of the cylinder, TDC.  There should be a line or mark on the crank gear.  The cam should also have a line or mark.  Install the cam lining up the marks on the cam and crank gear.

To be sure it is timed rotate the crank and follow the strokes of the piston.  Are you familar with 4 cycle engine operation?  If so just follow the strokes and make sure the valves are opening and closing correctly.

A tip for all 4 cycle engine timing is to check the valve overlap.  This will happen when the piston it at the top of the cylinder or very close to TDC.  Both valves will be open, just slightly, at TDC.  You probably can't see that the valve are open but you can usually rotate the valves with a lapping tool.  You may have to rotate and check for the overlap several times with the piston near TDC.  You will only see the overlap on one of the rotations.  

As for the blue oil, the valve guiedes could be wore.
Are you using SAE-30 oil?
Is this engine an overhead valve model?

Let me know.
Eric