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so.... ive been fixing up a kz900 here in monterey ca. and doing well so far thanks to a job and e-bay..recently the bike left me stranded after a ride to the coast with only starting on the inside two cylinders.2&3 i think...so remembering back twenty years- i ordered some cop bike coils cheap from e-bay .i installed a 3 ohm 1&4 coil and rode for a 160 miles on and off during the week.... now i'm on my third used coil, and yesterday it failed agian ...why are my coils on only 1&4 failing...i'm told the bike has a dyna elec.uder the points cover and i'm heading in there next ..anything i could look for or adjust.????...time for new ignition nip -or set?????? any way that a slow or fualty charging system cuold be the cuase???once years back a z would fail to rev when i had charging probs??/thanks and peace my fellow zed brothers and sisters...craig

Not exactly sure what would be causing that but the first thing I would do is check resistance on the coils. If its 3 ohms across the terminals like you said then I'm gonna guess it should be 16,000 across the spark plug wires. Just a guess though hope someone else knows what they are for sure. Also I would check how many volts are going into the coil. Should be 11 or 12 with the ignition on checking for DCV on the yellow/red wire. Its possible that your bike was only designed for 4.5 ohm coils two. If you have a manual I would look all this stuff up first before digging into the Dyna.

o.k i'll take note of the things you mentioned and start there.Your comments are greatly appreciated..sounds like i might be saying 3 ohms because i heard it somewhere..ha..ha i'll do some checking in the books and try and smarten up a little thanks again ..kinda not my strong suit hope i figure out the prob it's no fun not riding it peace..craig

One of the benefits of aftermarket ignition systems is the generate a higher open circuit secondary voltage to jump the spark. They also may be cranking the voltage on the coil windings higher than design value which can break down the insulation over time. Don't know if that killed yours, but it killed one of mine.

thanks...
I was thinking the same thing ..then the 1&4 continued to fail and not2-3 coil..i want to get a whole new ignition and coils..and have been watching e-bays dyna packages(new ones) with some interest..it would be a drag to put a new system in only to find that i burn the same set from some simple glitch i could have researched better and fixed...but your thoughts mirror my initial ideas as to the cuase...anybody going to the u.s red bull gp at laguna seca this year???i only saw one z last year there while glacing around at bikes..15 years ago i went and they had roped off an area..with some elrs and trick kzs ..any one know where the zeds gather at the event..peace craig

You might want to ask someone with a cop bike manual to look up the specs on the stock coils, I seem to recall reading somewhere that the cop bike coils are 2 ohms or so, and the Dyna requires three ohm coils. Maybe get some 3 ohm Dyna coils to go with your Dyna ignition?

Check out Z1 Enterprises, they have some good prices on Dyna stuff (along with other things).

thanks man,this is what i'm thinking too.i put about 800 miles on the bike in various stints while changing it after getting it about 6 months ago..i had just put a newer speedo and reset the trip meter on it at thesame work as the replacement coil(the guy before was a hack and had what appeared to match the cop coils in there allready... but they made it 800...now i get 150 miles or so on a ebay set of used ones and the problem returns. burning 1&4..hate to try a new dyna coil and burn it ..checking on some used green dyna 3 ohms now....your advice is helpful i'll check the specs peace craig