hey again ill be needing a ac cdi for my quad bike soon so ive googled around and found this circuit, only problem is i cant find anywhere that stocks the 15nf 250v capacitor, can it be replaced with something of a different value?

 

ukash -Please fill in the rest of your profile so we know where you live.

15 nF = 0.015 uF and is a common value available in both ceramics and films. Anything 250V or above will be fine.
http://www.mouser.com/Passive-Compo...z0vl8wZ1z0vk34Z1z0sq4zZ1z0vl8q&Ns=Pricing|0
http://en.wikipedia.org/wiki/Ceramic_capacitor which will work in this circuit but a film cap will work just as well and be less tendent to drift from the humidity and temperature variations a motorcycle is subjected to.
http://www.mouser.com/Passive-Compo...Z1z0vk34Z1yzu3quZ1z0sq4zZ1z0vl8q&Ns=Default|0

A lot of trouble to go through for a 4-cyl bike and you may not get the results you expect. If you look at my previous link to Ignitech as they'll have one off the shelf to fit your needs. They are not inexpensive by any means but having the capability to program them opens up a new (but perhaps dangerous) world if you try and advance your timing too far.

May I also ask which bike you're putting this in?

 

hi thanks for info and links, will sort profile out after this, its a 200cc 4 stroke quad bike which i paid £50 for so i don't really want to pay out a lot to get it working its just something to have a bit of fun on


-ash

 

hi thanks for info and links, will sort profile out after this, its a 200cc 4 stroke quad bike which i paid £50 for so i don't really want to pay out a lot to get it working its just something to have a bit of fun on

4-stoke is a lot different than 4-cyl (you said quad) so pick out a cap and go from there. Due to the sensitivity of the circuit I wouldn't alter from it much but it needs thermistor in the gate circuit to compensate for temperate. We've got another thread on this somewhere, try searching a bit.

 

Heres a circuit.

 

Hi Marshallf3, while were on the subject of CDI , the following is the circuit of a CDI module I pulled apart from a mucullock brush cutter, it was pretty simple It had a HV & trigger winding on the E core & a seperate IGN coil moulded on the side.

 

hi thanks, sorry quad here is a 4 wheel bike or quad bike, i think you call them atv's
what wattage resistors should i be using in these circuits?

cheers

 

Half watt should be more than good.