Pug timing sensitivity?

So I was talking to a friend today that said the timing on my 103 may not be as sensitive as I thought. His theory is that you have roughly 4mm of stroke while at top dead center. This in theory gives you 2mm of play either direction when setting the timing? Sounds shit to me but I just wanted another opinions.

I micrometered mine and right now I'm about .66mm BTDC. It seems to be running great but my question is will it gain power and speed if I time it to exactly 1.44 BTDC?

Re: Pug timing sensitivity?

Probably Fred /

Try 1 to 1.1 mm

1.4 is kinda high and more heat, more seize

But I don't have a pug just a puch the timing may be different so just watch your head tempature gauge if you advance that high

Re: Pug timing sensitivity?

It is shit. His theory is mathamatically and geometrically impossible. He might think there is 4mm of rotation where he can not detect vertical movement, which there is movement that is very slight, but it is not 4mm of stroke (which is vertical movement).

Flame front initiation is based on the roataion because the crank still rotates forward over the time it takes to propagate the flame, burn the fuel laden air and raise the pressure in order to push on the piston. Because there is a time lag between initiation and the raise in pressure you need to fire the spark before top dead center.

Starting to push the piston too late would be like trying to get a pedal bike to go fast but only pushing on the pedal when it is already part way down.

Trying to push the piston too early would be like trying to get a pedal bike to go fast but pushing down on the pedal before it even gets over the top of its rotation.

Stock setting is a compromise setting so it would spread the the goodness over a wider band. Setting advance from stock would be better for higher speed (at the expense of starting) and retarding it from stock would be better for starting and off the line.

Trouble also is the earlier you set it the more parasitic heat is retained in the motor, so if you have a goodly exhause you can use the heat better in the pipe then in the motor. Lots of people have played with the advance before and have a goodly idea of the range for each set up, basically you can go slight retard from stock if you have a pipe and gain both for starting and some top end when the pipe starts over stuffing the combustion chamber.

Re: Pug timing sensitivity?

Probably Fred /

You got it backwards

High timing good take off worse on the top

Low timing better on the top but wirse on the take off. Many stock cylinders/mopeds will run ok on almost any stator settings it seems like.

Re: Pug timing sensitivity?

If you advance your timing too much it makes you a retard.

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