What's the black box for?

[brucemg51]

It occurred to me while mowing the lawn that the motorbike has an extra part that my lawnmower doesn't. On the single cylinder Briggs & Stratton mower engine, the spark plug wire goes directly from the magneto to the spark plug. Whenever the mag makes a revolution, it induces a spark to the plug. Why do these MB kits have a CDI ignition unit? Is it really necessary for a single cylinder engine? Is it because the lawnmower engine is four stroke rather than two?

[Nomad]

yeah!! I'd like to know that too... maybe the lawnmower has an "internal" CDI..

[Caus-I-Can]

i think this is correct dont quote me but a magnetos spark is regulated by the fly wheel so its only option in incresing spark regulation is by increasing speed of motor by of course adding more fuel - hopefully u understand what i mean -

where as a cdi regulates voltage/ and speed of spark thus working in conjuction with fuel increase to deliver an all over performance improvement--

p.s. "WARNING' it is very very late were i am so i could be just raving

IF I'M WRONG PLEASE SOMEONE CORRECT ME SO I GET IT RITE

peace!!!

[Bikeguy Joe]

Yes, you are raving....

The mower does have a cdi or points/condenser set up. It's just not open to the eye like a bike engine.

The cdi on these bikes doesn't change spark timing, intensity, duration or anything else.

[Caus-I-Can]

So what is the differnece and for what reasons

[Bikeguy Joe]

Points are mechanical, CDI does the same thing electronicly.

[brucemg51]

Yes, now I think I remember seeing that the spark plug on mower engine is connected to a coil.