Cdi Questions

[yamaha125trimoto]

i just would like someone to tell me what a cdi box does how to test them (mine has 5 wires and its a 1988 polaris 250 2 stroke) and if theres any way to repair them ,bypass them or if anyone knows of a cdi box that would work with my bike

[bigredhead]

the CDI provides the spark you need for ignition ( Capacitor Discharge Ignitiion )

first... remove spark plug from cylinder head.. conect spark plug to wire.. touch the plug to the cylinder ( holding on to the rubber boot.. ) and pull the cord... do you get a visible spark ?

[yamaha125trimoto]

i have no spark the coil is fine the plug is new .025 gap kill switch bypassed

[yamaha125trimoto]

ANYONE i just want to know the general stuff about them mabie a diagram of whats inside of the actual CDI BOX

[yamaha125trimoto]

i dont understand why noone will help me out all i want is a general explanation on how a cdi box works but i guess thats just too tough for yall
thanks for nothing


P.S. I am not a newbie just havent ever had a bike with a bad cdi
and i would like to know more about them so i could figure out why
mine went out all of the sudden and what may have been the cause

[TwoHundredEx]

I'm not completely positive on this, but I thought I remember reading that there doesn't always have to be a cause for a bad CDI.
Electronics can go bad for no reason at all, they don't last forever. Also think I read that an improperly gapped plug could harm it. Like I said, not positve on that though.

Are you sure it's the CDI, and not something in wiring? Possibly a broken wire somewhere?
Eliminate all the small stuff first.

[The Goat]

calm down man, if i had to guess, you got water in it somehow or there is a loose wire.

[McDerry]

i dont understand why noone will help me out all i want is a general explanation on how a cdi box works but i guess thats just too tough for yall
thanks for nothing


P.S. I am not a newbie just havent ever had a bike with a bad cdi
and i would like to know more about them so i could figure out why
mine went out all of the sudden and what may have been the cause


Its a resin filled bakelight box with a Discharge Capacitor in it. The input line builds power in the capacitor, and is then released by the pick-up lines discharging it to the coil at a much higher voltage.

Its solid state.

When they go bad the capacitor itself goes bad.

[Ken99287]

i had a no spark problem on my atc because the wires from the pulse generator were being grounded when the seat smashed them into the frame. on the atc, that wire comes from the cdi cover to the main wiring harness right near the cdi.