TDC the measuring of.

[firekdp]

So, will it work ?

All methods will work. Use what ever you are comfortable with.
But until those with the "experience" come forward and explain why it isn't, I'll keep believing that the dial gauge is the most accurate.

[10 inch Terror]

So, will it work ?

All methods will work. Use what ever you are comfortable with.
But until those with the "experience" come forward and explain why it isn't, I'll keep believing that the dial gauge is the most accurate.

Good enough for me thanks very much...

[dirtyhandslopez]

Might not have said it clearly Firedkp.
But if you read again, I said tolerance differences could throw the whole "equation" out the window. "Equation" being the trig. equation. If the measurements aren't what they are supposed to be(ie 107 isn't 107 etc) then the end of the equation will be different than if the measurments are spot on.
Clear as mud now?

[firekdp]

Clear as mud now?

No, not really
How does the list of "crank rotation vs piston travel", that you obviously use, take into consideration the tolerance differences that you are worried about (if 107 isn't 107 etc.) . Especially since they are worked out by that "equation" . And especially since, a massive tolerance discrepancy will make a miniscule error in mm. So small, in fact, that once rounded up/down to 2 decimal places (which most gauges go to) it will read exactly the same.

[dirtyhandslopez]

Well then a, it doens't matter. 1' and a 1/8 arond the mag flange works for 23 btdc so 1' and a 16" is 19 btdc

[Strummer10]

INTERSTING question........i'm a bit fussy on my engine builds so I undertook a test using

1/ the industry produced gadget you screw down the spark plug hole

2/ a screwdriver pushed down the plug hole

3/ taking the head off, holding back the barrel and feeling with my fingers the piston as it approaches TDC and guestimating it

I've not tried the dial gauge method (which I guess is more scientific and on the money !!) as you have to take the engine out the frame

To be frank, the screwdriver seemingly wins hands down !!

To test all 3 options, I ended up with 3 sets of marks on my mag flange, but pretty much the centre point was the same ......

I think wot's needed is a device like yours that can be used with the engine still in the frame and perhaps a gauge attached to it...to definitively measure TDC......as getting it wrong can throw the timing out by quite a few degrees...I'm surprised there isn't a better proven method to do the TDC set up with the engine in the frame yet established in the scooter I industry, or maybe there is ?? does anyone know this ? IT IS perhaps the most important gadget for an engine build ?????

[firekdp]

Well then a, it doens't matter. 1' and a 1/8 arond the mag flange works for 23 btdc so 1' and a 16" is 19 btdc

As I said earlier, use the method you're comfortable with. If that is the method you understand, then it's the best one for you.

[Muppet]

1 and a 1/8 from where?

[starreem]

1 and a 1/8 from where?

From your TDC mark on your magflange

[Strummer10]

yes agreed there needs to be a more scientific gadget in the scooter world that accurately determines TDC.......if we all agree the 'dwell' period is irrelevant then that makes it easier (as some state above the TDC point stays in the same position anyway)....