Dirtbike Electrical System

[Homer88]

Hi there.

I'm trying to understand how the electrical system of my Yamaha WR200 works.

From my current limited knowledge, I've figured the magneto kickstarter creates a current which will fire the spark plug to ignite the mixture and it'll keep going on and on like the Energizer Bunny.

To be more precise, when I kickstart my bike, where does the current goes to until it reaches the spark plug??? I can't picture how does the CDI fit in, the distributor( if it's on a dirtbike's system), blah blah blah....

Most info. I found on the net relates to automobiles.

I hope someone can enlighten this Dude...

 

[Kawierider]

This might help a bit

Ok, i am not an expert on this but i do know how it basically works. The magneto generates the electricity......it then sends the electrical currents though the cdi unit, which condenses, adn strengthens the current....then its is quickly released through the spark plug wire in a quick pwerful burst to ignite the fuel air mixture....the part i dont understand is what the computer does......modern bieks have some kind of computer wired in to the ignition and i dont understnad its purpose or how it fulfills its purpose
tim

 

[Kramer]

I can add very little, but here goes....

the kickstarter turns the crankshaft, and the "rotor" that is mounted on it.

the rotor is magnetic and induces a current in the stator, coils of wire fixed to your crankcase half. Mounted either inside the rotor, or around it (depending on the desired flywheel effect).

That current goes here (they explain it better than I ever could).

Beyond the simple cdi box, I believe the computer "maps" the exact timing of the discharge by comparing things like sensed RPM, and throttle position. We'll have to look to someone more experienced for detail there.

 

[spanky250]

The ignition unit tells the plug exactly when to fire based on crankshaft position, rpm, and on some bikes, throttle position. The map programmed into the ROM chip is developed during the product development phase at the factory, both through extensive computer modeling, and testing, and even through experience.

 

[Kawierider]

ok, one more ?

ok, but on a bike like my kdx...ther is no sensor going to the computor for the cranckshaft position or anything for that matter......is cranckshaft position sensed by the pulses the indiviual magnets provide ?
Tim

 

[spanky250]

Re: ok, one more ?

Originally posted by Kawierider
ok, but on a bike like my kdx...ther is no sensor going to the computor for the cranckshaft position or anything for that matter......is cranckshaft position sensed by the pulses the indiviual magnets provide ?
Tim

The KDX ignition is analog, not digital. The ignition is energized by the magnets as they pass over the stator. The placement of the magnets in relation to the position of the stator determines basic crankshaft position, the ignition box then adjusts the spark timing by rpm. Not at all like the digitally mapped ignitions on modern MX bikes.

 

[Homer88]

Mine is a 92 WR200.

And I was thinking of changing the stator or coil kit to make it provide more power for my Acerbis DHH light.

So does this "analogue" method when fitted with an aftermarket stator or coil kit make the ignition haywire?

Any simple DIY methods that I can do to make it product more power?

 

[spanky250]

Originally posted by Homer88
Mine is a 92 WR200.

And I was thinking of changing the stator or coil kit to make it provide more power for my Acerbis DHH light.

So does this "analogue" method when fitted with an aftermarket stator or coil kit make the ignition haywire?

Any simple DIY methods that I can do to make it product more power?

There are two coils attached to the backing plate on your bike. One is for the ignition, the other is for the lights. They are seperate circuits.

 

[Homer88]

After reading some articles here's what I think is happening...

The flywheel has a magnet in it and it is spinning round a stator with coils in it. This induces current to flow to light up the electrical stuff on the bike ie. Headlights, signal lights, rear brake light etc.

On the other hand, there's another wiring from the flywheel to the ignition that will from the magnet position, determine the crankshaft position and ignite the spark as accordingly?

Correct?

 

[spanky250]

Close enough.:)

 

[Homer88]

Thanks all for the replies especially the "new" link.

One more question, saw this product that claims to make your headlight brighter just by plugging in some wires.
Is this possible ???