January 21, 20197 yr Hello- I am stalled in rebuilding a spare kt250 engine that was seized. I have rebuilt the lower end, and before I spend the money for a bore and new piston, etc., I want to make sure I can get a spark. I have the flywheel installed, and I have a CDI unit, but I do not have a coil. I'm looking for an aftermarket coil but I can't find out whether I need a 12v or a 6v coil. I know the lights are 6v, but the ignition coil on the magneto may not be 6v as well. Does anyone know which voltage coil I need, or maybe which coil specifically I could use? I found a couple of reasonable coils on ebay that say they are compatible, but I'm skeptical. And of course the used kt parts on ebay are usually shot AND super expensive. I think it's a cartel...LOL Any help would be appreciated, Larry
January 21, 20197 yr I'll have a look at mine and see if says anything useful on the coil Edited January 21, 20197 yr by feetupfun
January 21, 20197 yr Ignition coils for CDIs are neither 6 volt nor 12 volt. CDI coils work on a completely different principle than "induction coils". The capacitor inside the CDI gets charged to on the order of 200 - 300 volts, and then is discharged into the ignition coil. Technically, such ignition coils are "pulse transformers". They typically have somewhere around a 1 : 100 (primary : secondary) turns ratio. Their primary resistance is very low (usually under 1 ohm). I just searched "CDI ignition coil" on eBay and found something for $8.25 USD shipped from China. Better yet: https://www.ebay.com/itm/IGNITION-COIL-YAMAHA-TTR125-TTR125L-TT-R125-TT-R125LE-2000-2009-2011-MOTORCYCLE/281087430819?hash=item41721dd0a3:g:iFIAAOSwDk5T1Lw~:sc:USPSFirstClass!55066!US!-1 Edited January 21, 20197 yr by konrad Added content
January 21, 20197 yr Author thanks to Konrad and feetupfun for the replies. I did look at the ebay link, and that coil, though cheap says it is not compatible. But, I have a feeling that the compatibility may be based on physical dimensions and not on electrical factors. I think I'm going to order one from ebay that is like $19 but says compatible. I can make it work physically one way or another, so I've got my fingers crossed that it will make a good spark, and if so, I can proceed. I'll let you know how it works out...Larry
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