The backstory: I'm new to motorcycling, having only recently inherited a 1984 GPZ550 from my uncle. It's a wonderful bike and runs great. Too well, in fact. I wanted to improve my mechanical skills, so naturally when a 1983 GPZ250 (EX250-C on the VIN) non-starter went for sale near me I had to take the opportunity. The bike is in good condition for its age, the only real cause for concern the fact that it hadn't been started in 8 years. Compression is good, I bought a new battery and the starter turns over freely, but my problem is no spark.
First I checked and cleaned the electrical connections, confirmed there were good grounds and replaced the spark plugs. No issues there. In order to test the electrical components I first had to hunt for the service manual for this particular model, as the 1983 model appears to first in the 250cc series to feature electronic ignition. The pdf manual for the KZ250 & 305 years 1979 – 1982 freely abounds online, but I had to find a physical copy of the manual which also covered the relevant1983 and subsequent supplements. I intend to unbound, scan and upload this manual to share with the internet hive-mind once this bike is up and running.
I followed the manual instructions and performed resistance tests for each of the components in the ignition circuit; pickup coils (which perform the spark timing from the crank shaft), exciter coils (which induce current from the crank shaft to charge up the CDI box capacitor), CDI box and ignition coils.While there’s a whole table of readings for the CDI box I can’t get a single sensible reading from my multi-meter. I borrowed a few better quality multi-meters to confirm it wasn’t just my cheap meter. The manual does say that only the “Kawasaki Hand Tester 57001-983” should be used to measure the various resistances of the CDI box, as other testers “may show different readings”, but I have no idea how or if one could even get access to that kind of thing anymore? Still, it’s a dubious result for the CDI box, but doesn’t rule out any options.
As for the other components tested, I’ve compiled their specified resistance ranges and my test results below:
Pickup Coil – Range: 8.5-12.9kohm. Reading L: 12.4kohm. Reading R: 12.3kohm.
Exciter Coil (High Speed) – Range: 2.5-7.5ohm. Reading: 6ohm.
Exciter Coil (Low Speed) – Range: 2.7-4.1kohm. Reading: 3.3kohm.
Ignition Coil (Primary Winding) – Range: 0.18 – 0.28ohm. Reading L: 0.8ohm. Reading R: 1.4ohm.Ignition Coil (Secondary Winding) – Range: 3.2-4.8kohm. Reading L: 8.3kohm. Reading R: 8kohm.
To summarise; my Pickup coils are on the high side, but still in spec. The exciter coils are comfortably within spec. The Ignition coils are sadly well above spec, although the appear to be in good condition with minimal rust around the exposed iron core. The specified primary resistance range is also dubiously low. In my research I’ve haven’t been able to find any reference to such a low primary resistance for a coil.
Before I can attempt to draw conclusions and suggest possible next-steps, I have two more pieces of confounding information to share.
Firstly, during my initial optimistic attempts to try starting the bike with the carbies connected, after numerous unsuccessful attempts while feeding it mouthfuls of ‘Start-Ya-Bastard’ it did managed to start up and run for ~20-30 seconds on one occasion, and not again.
Secondly, while cleaning and testing the connections in the ignition circuit I observed the following strange behaviour: when I disconnected the wire supplying power from the CDI to one of the ignition coils I would get a bright and consistent spark from the opposite coil. When I reconnect the power to ignition coil I get a single spark and then nothing. This behaviour is consistent with either coil disconnected.
I’m sorry to ramble on, but I hope this all helps to paint a picture. The behaviour suggests to me that either the capacitor in the CDI box is giving out and as a result is struggling to produce sufficient charge to power both ignition coils, or the CDI box is fine and that simply the increased resistance of the ignition coils is too much for the circuit to overcome. Maybe it’s a bit of both.
Anyway, my question is; what next?
I’ve found original coils on ebay, but I don’t particularly feel like blowing $200-$300AUD on 40yo coils that are quite likely not much better than my current ignition coils. Same deal with a replacement CDI. After lots of googling I’ve also managed to get a quote from a company called ‘Vectriq’ that claims to specialise in ECU repair. Still, that’s ~$200AUD to troubleshoot and tell me that my CDI is fine, or $400 to repair and still have dodgy ignition coils.
I’d rather a cost-effective repair than maintaining authenticity, seeing as this is an under-represented and not particularly sought after model. Should I give up on trying to make the current ignition system work and throw it out in favour of replacing with a Dyna-S ignition? Another point of interest for those who’re still reading this far on; unlike all the other motorcycles I’ve looked at so far, the stator, pickup coils and ignition timing setup all sit in the engine oil. The oil seal is in the engine side cover which is removed to access these components. Is this a common configuration? Would a Dyna-S even work in this environment?