AJS & Matchless Owners Club

Hi

I am refurbishing a K2F magneto and would like to confirm it's function before refitting to the bike. The theory suggests that if I fit the HT leads and plugs, grounding the plugs to the mag body, the mag should produce sparks when rotated.

Should I expect to see sparks just turning it by hand or will I need to spin it faster or for a longer duration?

Oh! and am I leaving myself liable to become a ground and subject to electrical stimulation

Regards Mick

I've managed to get a spark on a refurbed mag by just finger twiddling it over the max flux 'flip' point. No electrical shock.

Agree with Nev, a good mag will jump 1/4" easily by hand , bright blue spark
my refurbished mag still does that after 10 years while waiting for me to do the rest of the bike

Agree with the comments above "a flick of the wrist" should be enough to generate a good spark, Groily will confirm in due course.

Colin

Lucas's standard for this magneto is to jump a 5.5 mm gap, full advance, turning 150 RPM, with under 5% miss. This is best replicated with a motor driving the input shaft, but easily tested with a dozen turn of string around the shaft, and a slow steady pull.

Ciao, DC

Yup, and a good one might do rather better. 100% sparks at 130-140 is what I always aimed for, and sometimes have seen 100% at 110rpm using three point 5,5mm test gaps per Lucas. Advanced, and at room temperature that is. At a test temp of c 50°C, it will drop off a bit, but if it won't perform hot under about 180rpm without missing, fully advanced, I'm not happy. Retard will add a good 30-50rpm to the figures, depending on exact amount of movement on the camring, and the quality of the spark will reduce a bit too. The later steel contact breakers will often be marginally better at very low rpm - although I personally far prefer the brass type.
A flick of the wrist should be good . . . as long as it's turned the right way, which is anti-clock on any K2F on our bikes.
If there is any way of testing the interval between the 2 sparks, it's a good plan . . . can be done with a strobe on the bike of course. But worth doing because K2Fs are the world's worst for not delivering at 180:180°. Errors of 3, 4 or even 5+ degrees at the mag are not rare - and that has to be doubled up as the mag goes half speed. Six, 8 or even 10+ degrees of timing error between cylinders ain't good . . . .

Thanks Guys

Always nice to know what to expect This is my first magneto bike so a bit of a learning curve, very pleased with fat blue sparks at very little rotational speed

Regards Mick