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CDI Schematic

First and foremost, All AC-CDI needs a KILL switch in order to stop the HV generator to supply power on the CDI that charges the capacitor, normally kill switch is just a switch in where one end of the terminal is connected to that when pressed will send the current to ground disabling it.

Some AC-CDI circuits schematic diagram that may be useful in search of a DIY cdi circuits. In order for this to work with your machine, be sure its an where a HV generator is needed from your stator. aside from the low level voltage that charges your battery. Can be used on 50cc all the way up to 250cc.

2 stroke CDI schematics

SUZUKI RM85 (old models)
DC-CDI using lm2587 

This is another AC-CDI schematic, without an MCU that can adjust the advance curve or mapping of the ignition timing. The circuit is not that difficult to assemble and no tweaking whatsoever by PC for full performance.


The CDI is in need of an external High Voltage Generator to charge the capacitor C1, that will be dumped to the ignition coil at the right time by the SCR Q1. When a pulse arrived at pin 1 of the cdi connector, the pulse is clipped to not more than 5 volts by D5 and D6. Q7 and Q2 is the pulse shaper, Q4 is the scr trigger.

In order to cut the High Voltage supply and stop the ignition entirely. D1 will be shunting the generator to ground, stopping the flow of voltage and current to D2. thereby disabling the engine. Without the kill switch, even if u off the ignition switch on an AC-CDi, the engine will still be turning because the circuit is still alive via R1 to which supply low voltage to the whole circuit in dependent to the High Voltage input. That is why the kill switch is commonly connected to other terminal of the ignition switch.


Resistors all 1/4watts otherwise specified
R1---30k 1/2 watts
R11---500 ohm


C1---1.5uf /400V
C2---100uf /10v or 16v
C3---0.33uf or 334
C4---0.1uf or 104
C6---0.015uf or 153
C8---0.033uf or 333
C9---0.068uf or 683


D4---8.5 volts zener/ 500mw
D5, D6---5.1v zener / 500mw


Q1---BT151-600 SCR
Q2,Q4, Q6---2n5401
Q3, Q5, Q7---2n5551


Reinaldo Guerra said...

tenho 1 motor popa suzuki 15 hp preciso de 1 cdi ano 2009 brazil Reinaldo may name.

Reinaldo Guerra said...

preciso de 1 cdi enginer popa suzuki 15 hp ano 2009, Brasil tks

Unknown said...

Hello from Kuwait,
ERRATA ; Diode in question for suzuki rm80 cdi schematic is D4 (ZENER). May I know the voltage value of the zener diode?

Thanks again.

Edgardo M. Diolola (Philippines)

Nathaniel Berdan said...

Edgardo, D4 is 4.7v - 5.1 volts zener of at least 500mw it should be enough to clip undesirable voltage the pick up coil generates when revving the engine.

Unknown said...

Nathan, thanks a lot, more power to your works.

Edgardo (Egay)

Gerhard Nel said...

Hi, I would like to know what us the cross reference for fr25g?

Nathaniel Berdan said...

Gerhard Nel you can use BT151-500, or any other SCR that has the 12A-500 volts specification.

Gerhard Nel said...

I appreciate your blog! Would you be able to help with a Kawasaki klr 600 Cdi?

herry said... have schematic cdi mio 5tl??? tks

herry said... have schematic cdi mio 5tl??? tks

冠強調 said...
This comment has been removed by the author.
冠強調 said...

sir I want the buy (real )racing cdi (rpm fast and powerful ).can you make one for me ? I don't care how many much . so are you ok ?