MOPED ARMY

As I stated David ... some dirt bikes come with the mounting holes slotted from the factory... that would be Yamaha and Kawasaki... Honda and Suzuki you have to slot the holes.

And it is not just theoretical.... I have altered mine for more low end performance by advancing it a little.... On a modern dirtbike, you advance a little for more low end and less top end. And retard it for less low end and more top end.

Which is the opposite of what you have been reading here by people other than me... which is why I have not agreed with the popular opinion here

On another older 2 stroke racebike... I played with the timing 3 or 4 times... and got detonation (pinging) every time I got away from stock specs very far either way... Both too far advanced and too far retarded caused temperature to rise in a bad way.

That is why my opinion is that pretty close to stock is best.

And I don't believe mopeds are set with "bad" timing on purpose.

Because the BTDC timing measurement is specified by the book... and those measurements are almost the exact same as the older point ignitions on 2 stroke street and trail motorcycles.

Here are some examples

50cc...... 1.6mm

100cc..... 1.7mm

175cc..... 1.7mm

(and those are fixed timing motorcycle ignitions.. no kind of "advance mechanism built in)

And the 2 peds reported here were 1.5mm and 2.0mm.

So they are not "retarded".

I will come back with a link Dave...to a description of how to change timing on a 2 stroke dirtbike from a world reknown 2 stroke engine tuner.

Here it is David >>

http://ericgorr.com/techarticles/basic_two_stroke.html

Cut and paste that into your address bar and go there and read all about 2 stroke tuning.... By the BEST there is.

The part about ignition timing is towards the bottom.

Fred,

OK, I read it and I'm still confused. This guy has to be leaving something significant out of the equation.

I also went back to my old 2 cycle tuning book and it says that higher rpm power bands can support more advanced ignition timing. If this guy is right about losing top end power then there has to be something going on that he is not describing too well.

As an example, as rpms increase, the cylinder volume increases faster, if the burn rate of the fuel/air mixture does not increase, this should lower the cylinder pressure. What does this guy know that he is not telling us in his explaination?

By the way, most peds run at fairly low rpm, which he may refer to as mid-range, so maybe advancing the ignition a liitle is not too bad.

Ron

Fred,

Maybe electronic ignition is the reason.

Anyway, I'm leaving for bike week now.

I know, I'm a little late, but I hear the sun is still shining and I need a ride.

Signing off for a week or so,

Ron