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Post by posereddie on May 27, 2008 5:57:21 GMT -5
'78 SR, I have no spark. I have replaced the CDI unit because I thought I fried it by hooking the regulator and CDI plug up backwards. The readings across the coil are good. The readings across the magneto windings are good. I understand a battery is not necessary to run the ignition (though my wiring and batt are sound). The magneto must have a permanent magnet. How do I check this? I have read every message on this board. Problems are solved by replacing this or that, or finding a poor wiring connection. I had a similar problem with my XS, rewired the rotor and found it interfered with the ignition's magnetic pickups, so just retro-d a points set up onto it and hooked up a boyer. Is reverting to points cost effective? I hate to just keep guessing. Anyone have a definitive way to verify the magneto is square? I'll go on from there. Thanks! By the way, I have 5 bikes. If They all crapped out on me I'd freak. This bike is the lightest and most fun and I miss it! That's saying a lot for a little 500. Thanks again.
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Post by aero on May 27, 2008 7:19:50 GMT -5
If the CDi box is good and the megneto windings measure OK what's the other thing left in the system? Apart from what connects it all together!
You can't easily convert the SR to points and if you did I'd guess you'd be using XT500 stuff, which would mean a low powered generator not really up to powering a decent headlamp without alot of messing about. Even then the results are marginal.
I wouldn't have thought your magnets are the problem, unless someone has welded the rotor.
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Post by malakiblunt on May 27, 2008 11:56:54 GMT -5
Cheak your earths! 9/10 its the problem with non functioning electrics.
i bet it will be something emberasingly simple, i shelled out for a new regulator for my XS only to find out the id just conntected the old one up wrong !!
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Post by stevec5000 on May 27, 2008 13:58:08 GMT -5
There aren't really any earths involved with this system except for the kill switch, the wires from the magneto go right to the CDI and from there to the coil. Perhaps he has a short on the wire to the kill switch or ign. switch that permanently kills the spark? If the kill switch wire isn't grounded the engine should fire when it's kicked over. The 4 outputs from the magneto can be checked with a 'scope to see if you get a pulse when it's kicked over, black wire is common to all four. If you do get a pulse on all four outputs then your CDI or coil is likely to be bad but if the CDI has been changed that only leaves the coil. The coil can be ohmed out or tested on a coil tester. Also, don't overlook the spark plug wire and cap. They should be ohmed out since the resistor in the cap frequently goes bad.
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Post by malakiblunt on May 27, 2008 15:58:40 GMT -5
defintly worth continuity testing all the wires.
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Post by posereddie on May 27, 2008 18:39:14 GMT -5
Awesome replies! Stevec5000 has made some good points -
W/R to B: 17.5 Ohms (good)
W/G to B: 94 Ohms (good)
R to Br: 5.8 Ohms (good)
Br to B: 336 Ohms (good)
These are the magneto/alternator readings, good A/P the Haynes manual. The coil primary and secondary were within specs. I replaced the cap because I took the original apart and the spring and spacer went SPROING! I replaced it with a Honda lawn mower type. I don't suppose that should be a problem??? Yo, it definately would be embarrassing if it were something simple, like a sparkplug(!!), I certainly have no way of checking for the "pulse." I plan on a THOROUGH investigation. I GOTTA get this thing running. By the way - it was mentioned that the black wire is a ground for the 4 wires, as you can see, the Haynes manual only gives ranges for three to the black wire, then one R to Br. Keep this thread going, I apreciate the input!
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Post by posereddie on May 27, 2008 18:46:04 GMT -5
Crap! Just read over the Haynes manual! I haven't checked the R to B, which is the 4th output wire that Stevec500 had refered to. The machine is at the shop at work, I'll check it tomorrow. Frankly, I sure hope it's just something I overlooked, like the kill wire on the CDI shorted to ground, or the wire to the coil open. Oh, please, everybody think good thoughts!
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Post by stevec5000 on May 27, 2008 18:55:06 GMT -5
Awesome replies! Stevec5000 has made some good points - W/R to B: 17.5 Ohms (good) W/G to B: 94 Ohms (good) R to Br: 5.8 Ohms (good) Br to B: 336 Ohms (good) These are the magneto/alternator readings, good A/P the Haynes manual. The coil primary and secondary were within specs. I replaced the cap because I took the original apart and the spring and spacer went SPROING! I replaced it with a Honda lawn mower type. I don't suppose that should be a problem??? Yo, it definately would be embarrassing if it were something simple, like a sparkplug(!!), I certainly have no way of checking for the "pulse." I plan on a THOROUGH investigation. I GOTTA get this thing running. By the way - it was mentioned that the black wire is a ground for the 4 wires, as you can see, the Haynes manual only gives ranges for three to the black wire, then one R to Br. Keep this thread going, I apreciate the input! That must be a misprint in the manual. It should be Red to Black (not brown) equals 334. I checked it and got 354 but all of mine read slightly high. |
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Post by posereddie on May 28, 2008 7:15:02 GMT -5
Stevec5000: You're correct, R to B and Br to B should show approx 330 Ohms. The third reading it calls for is R to Br which should show 3.5 to 6.5 Ohms. In an earlier life I'd have taken this all apart and learned something. Many times I learned I shouldn't have torn it apart. I'm hoping to come away from this as knowledgable as any of you about this, so pass on your dope concerning this convoluted system. Thanks.
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