If there is enough slop in a crank to make TDC an issue when a piston is at TDC, then you need a new crank and bearings.
No the srobe was not being used that is how miserable my degree scale was printed.
Once you have done all of this you ride it up a hill and advance the timing until it pinks then back it off a little!!The reality is that there has to be crankshaft movement while the piston is at TDC. So it totally depends on the accuracy you are seeking. You can 'find' TDC by: holding your thumb/finger in the spark plug hole and feeling when compression stops; you can 'find' TDC sticking a pencil/screwdriver/whatever in the spark plug hole and observing the point where it stops moving; you can use a bubble as described. Depending on what you are trying to do, any of those methods can work perfectly well.
Yes, you can misread a degree wheel or do the math badly but it's about as basic as math gets...determining 1/2 of a number. The biggest IN-accuracy issue using a piston stop/degree wheel involves the size of the wheel and the diameter of the pointer. If you print out a 4 1/2" 'degree wheel' from the internet and adhere it to a CD - which seems to be a fairly common recommendation - and use a piece of 12 Gauge Romex copper ground wire as your pointer, you have very closely-spaced indices and a pointer that will probably cover 4 degrees! Heck, it's probably LESS accurate than watching the pencil move up and down! OTOH, a 12" Moroso wheel with a sharp pointer will be dead-nuts accurate.
I am NOT saying that other methods don't work but on an accuracy scale, the degree wheel/piston stop is the most accurate. Yes, I admit that assumes it's a decent sized wheel/pointer and the operator knows how to do it.
No the srobe was not being used that is how miserable my degree scale was printed.
The 850 Mk3 scale has a small range of adjustment, however, I'm not sure if it fits (or can be made to fit) earlier models?
https://andover-norton.co.uk/en/shop-details/16351/ignition-timing-degree-scale-850-mk3-only-
Once you have done all of this you ride it up a hill and advance the timing until it pinks then back it off a little!!
Once you have done all of this you ride it up a hill and advance the timing until it pinks then back it off a little!!
The reality is that there has to be crankshaft movement while the piston is at TDC. So it totally depends on the accuracy you are seeking. You can 'find' TDC by: holding your thumb/finger in the spark plug hole and feeling when compression stops; you can 'find' TDC sticking a pencil/screwdriver/whatever in the spark plug hole and observing the point where it stops moving; you can use a bubble as described. Depending on what you are trying to do, any of those methods can work perfectly well.
Yes, you can misread a degree wheel or do the math badly but it's about as basic as math gets...determining 1/2 of a number. The biggest IN-accuracy issue using a piston stop/degree wheel involves the size of the wheel and the diameter of the pointer. If you print out a 4 1/2" 'degree wheel' from the internet and adhere it to a CD - which seems to be a fairly common recommendation - and use a piece of 12 Gauge Romex copper ground wire as your pointer, you have very closely-spaced indices and a pointer that will probably cover 4 degrees! Heck, it's probably LESS accurate than watching the pencil move up and down! OTOH, a 12" Moroso wheel with a sharp pointer will be dead-nuts accurate.
I am NOT saying that other methods don't work but on an accuracy scale, the degree wheel/piston stop is the most accurate. Yes, I admit that assumes it's a decent sized wheel/pointer and the operator knows how to do it.
Racing Yamaha 2-strokes, TDs, TRs and TZs where ignition timing is far more critical, a dial indicator with a spark plug hole screw in adapter (sold by Yamaha for the purpose) is all we needed to find TDC accurately enough. Just saying.