I'm hoping there's an electrical guru out there who can help me with the wiring of my coil. I have a 48 sport running 6v electrics. I have had to re-wife the whole bike as the loom had rotted away in a ditch so used this wiring diagram ... The coil I have has an HT lead to the plug obviously and two terminals. Does anyone know whether it makes a difference which terminal I connect to which wire in the diagram, are they interchangeable as such? Does the wiring diagram look correct too with one terminal of the coil going straight to earth? The juice is provided by a motoplat rotor/stator and points btw. Any coil experts out there who can educate me it'd be much appreciated. Thanks
If you posted the wiring diagram it would help! Coils usually have one terminal marked "+" and the other "-". If it's a negative earth bike the + terminal goes to the supply and the other to the contact breaker. But if the power is provided directly from a magneto coil it may be different. If you connect the coil the wrong way round the spark will jump from the spark plug body to the centre electrode instead of the other way round. On a bike with a marginal ignition system this may make starting harder and/or lead to plug fouling.
Bl00dy apple iOS stopped me doing that on the ipad Derek so resorting to an old fashioned PC to upload it. Grrr. The coils are tiny things two spade terminals one at each end but no markings on any of the three I have so it's impossible to know which is +ve and which -ve. I assume the bike is negative earth based on the diagram and the fact it's a ducati...
I think I've found your diagram online. And yes, one side of the coil is connected to ground and the other to the magneto coil. Although not shown, the points will be in series between the magneto coil and ground, completing the circuit and there should be a capacitor across the points. If the coil terminals are marked I'd connect the "-" one to earth.
You're right Derek there is a capacitor/condenser across the points too - that is another area of suspicion. I've checked the coil resistances and they look good so I think the coil is ok but I can't get a decent test on the condensor. All that happens is if I connect to a battery, when I touch the second wire t the condenser case it sparks.
Ah. I see it now, different diagram but same idea. 15 is the standard number for the +ve ignition feed, I'd connect that one to the magneto and the other to earth.
You can't easily test a condenser. If you connect a meter reading resistance to the condenser it should read a value which will increase as the as the condenser charges up, probably starting in the 100's of KΩ and getting much higher. Once it has charged you won't be able to check it again unless you reverse the connections, or discharge the capacitor. Some modern digital multimeters can read capacitor values. I think they are about 0.25 µF. Here is an article about ignition capacitors which might be useful - Capacitors in Ignition Systems
Wow! I never knew 15 meant that, superb stuff and it means I'm connected correctly too so only the condensor could be at fault now. Thanks Derek, you're a superstar!
All the auto-electrical standard numbers are listed here - DIN 72552 - Wikipedia, the free encyclopedia
Thanks for those links too, great resources. I wish I understood electrics better so these will help a lot. Thank you so much for your help!
Derek, the points are shown on the wiring diagram within the generator. In reality they look something like the attachment with the condenser installed (courtesy of Pete). If Ducati have issues supplying one, get a new spare from a Mini for a quid or two and adapt the connections/make a bracket. IIRC the Mini ones were 0.2µF. They tend to fail to open circuit so are easy to test by temporarily connecting any suitable sized capacitor (poly/metal ones for Maplin will do) parallel to the suspect one.
Thanks Denzil, I've been eyeing up the mini condensers in Halfords so that sounds promising. I'm hopefully close to solving the oil,lead from the pedal shaft now so then it'll be full steam ahead to test the electrics...cheers!
Yes I know, but when I was replying the OP hadn't at that time succeeded in posting the diagram. I found a similar one for the same bike on-line but it didn't show the points.
Thanks for that information - I have been having a few problems with my old 851 and wanted to check the coli connections but was puzzled by the markings. Now I know!
