Head Repair

[Barry]

Some years ago we had a discussion about accurately determining TDC and the Micro tool was mentioned. I punched the numbers into a piston position calculator ad determined it would be a challenge  to make it  work very accurately as at TDC a 1 deg rotation of the crankshaft produces only 0.00024" of piston movement which is less than bearing clearances.

If anyone wants to use the tool for it's intended purpose the static timing mark at 6 Deg is 0.00848" below TDC.  It would be more accurate at this piston position as 1 deg error now produces approx. 3 thou of piston movement.

When I crunch these numbers it always surprises me how very close to TDC the piston is when the fire is lit by the spark. Even at full advance the piston is only 0.232"  below TDC

[montmil]

Tony, I too have a vintage Micro-Time tool. Still have the booklet that came with it -giving what mark on the plunger should be 'locked in' for timing a Yamaha DT-1, etc. Been in my tool chest for over 40 years.

Mine was purchased to use on a Bultaco Sherpa-T, 1975 seems a long, long way away now.....

but i think you are a few years older than me.

That was uncalled for. Be nice to your elders