Jean-Pierre, Quite a lot has happened since I wrote the message you responded to. In the end, I simply swapped the two coils and the problem moved from the 1 & 4 plgs to the 2 & 3 plugs. I believe that this proved that one of my two coils was bad. I have another one on it way to me now so in a day or two, I will know if this theory is correct.
Thanks for your thoughts. Dennis G. - Seattle -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: 08 June, 2009 01:56 To: [email protected] Subject: [Nighthawk Lovers] Re: My CB700SC and the CDI unit Hello At that point, I would make a harness to connect the pulse generator to the cdi unit, allowing to measure the signals of the pulse generator on an oscilloscope. Simple to do with faston clips. Making the same type of harness on the output of the cdi to the coils would allow to monitor the output signals. Seing both pulse generator signals on the scope would allow to check for integrity (up to the harness). Monitoring on each pair of cylinders the input/output of the cdi would allow to check for it's integrity. And if you get two good signals to the coils and still no spark, the problem comes from the coils / their ground connection / the wires / the spark plugs. If you don't have an oscilloscope, ask somebody in electronics business : lot of people have old ones at home. You can even find now, on ebay or else, cheap multichannel scopes which are just peripheral of computers. By the way, I would not rule out so fast the fact that different cdi units could loose preferably one channel, always the same : could be normal with lost of capacity of electrolytic capacitors, given such or such design. Like getting too low water pressure feeding a a washing machine would always make the same type of apparent defect. I discussed this week end with a friend, amateur of cars of the end of the seventies / beginning of the eighties. Had the same problems with one of his cars cdi... ended up in changing the electrolytic capacitors. I was on the way to make this type of diagnostic on my 650 CBX, when abruptly, this week end, it failed : no more sparks at all. Had to go and take it with the car and trailer, fortunately close from home. Will see later what happened. Regards JPD At 19:46 05/06/2009 -0700, you wrote: >Well, my new Ignitor unit came and I installed it and my bike still has >the same symptoms. That is, cylinders 1 and 4 are not getting any spark. > >I sat down and had a longer look at the schematic and I can see some >possible scenarios that might be consistant with the facts on hand. > >Those facts are: > >- I've measured the resistances of both my primary and secondary coils >and >my pulse generator coils and they all show continuity and resitances that >are within spec. > >- I've tried two different Ignitor units (my original and the new one) >and >the system fails the same way with either (no spark on 1 & 4). > >Scenario # 1 is that the new ignitor unit is bad in the same way that the >old one is, i.e. failing on the cylinder 1 & 4 side. I don't think much >of this idea however - seems like too big a coincidence. > >Scenario #2: that even though the pulse generators both measure good >on >continuity and resistance, the one that sends the signal for 1 & 4 may, >somehow, be out of place relative to the central shaft that spins with >a magnet on it to generate the pulses. I'll be able to see this, I >think, by cranking the bike and looking for voltage pulses coming up the >cable from the pulse generators. If both sides have similar pulses, then >I think this won't be the issue. If one pulse is low or mssing, then I'll >open the pulse generator cover and see what's what in there. > >Scenario #3: one of the connectors linking the pulse generator cable to >the Ignitor may be corroded and not passing signal. Frankly, this seems >remote to me. The surfaces seem clean and I've plugged and unplugged >them several times. > >Scenario #4: The wire that carries the 1 & 4 signal from the ignitor >to >the 1 & 4 coil may be open. I can run a simple continuity test to demo >this. I know the ground wire and the 2 &3 wire from the ignitor to the >coils has to be good as I've got spark on 2 & 3. > >Scenario #5: The wire on the coils that carries the ground from the 2 & >3 >side to the 1 & 4 side may be open. > >Scenario #6: The connection where the 1 & 4 signal from the ignitor >connects to the 1 & 4 coil may be corroded and not passing the >signal. I've had this disconnected and reconnected and it seems unlikely >to me like in #3. > >Dennis H., are you reading this? I'm looking at page 19-0 in my CB700SC >manual and I'm wondering if I'm missing some other scenarios? > >Dennis >- samadhi<soft|coda|muse>.com > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/nighthawk_lovers?hl=en -~----------~----~----~----~------~----~------~--~---
