ignition loop - coil '78 XS650E

Kevin Werner

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From the Tech Section Are you checking both points sets?

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arcticXS

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If the orange points wire is on your left coil, perhaps disconnect it at the connector next to coil, then turn key on and tap the orange wire to bare metal ground (make jumper if needed) - see if spark is produced at plug inserted into cap (bypasses points and condenser)
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I have thought about whether the point is grounding too - I have a new set so I’ll replace the left side first and see if that makes a difference, before doing more measuring.
That is VERY simple to check. Disconnect the capacitor/ condenser, but leave points connected. And coils connected both to power (brown) and to points (Grey/orange) Then turn engine so the points close. Connect voltmeter + lead to coil negative side (grey or orange, depending on what side you're checking. Voltmeter - lead to any good ground on engine, i.e cylinder head fin. With ignition and kill switch on, you should see less than 1-2 V . To check the supply voltage to coil, move the + lead to the coil positive side, with everything still connected. Now you should see very close to battery voltage. If not, you have one or more poor connections.
Note that it is not very useful to disconnect the brown wire and check the voltage with no load on the circuit. The coils draw around 3 amps, so any resistance in the supply to coils will reduce the available voltage across the coils significantly.
 

Niels B

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That is VERY simple to check. Disconnect the capacitor/ condenser, but leave points connected. And coils connected both to power (brown) and to points (Grey/orange) Then turn engine so the points close. Connect voltmeter + lead to coil negative side (grey or orange, depending on what side you're checking. Voltmeter - lead to any good ground on engine, i.e cylinder head fin. With ignition and kill switch on, you should see less than 1-2 V . To check the supply voltage to coil, move the + lead to the coil positive side, with everything still connected. Now you should see very close to battery voltage. If not, you have one or more poor connections.
Note that it is not very useful to disconnect the brown wire and check the voltage with no load on the circuit. The coils draw around 3 amps, so any resistance in the supply to coils will reduce the available voltage across the coils significantly.
Thanks will get back on the ignition soon - right now I’m banned from the garage until at least tomorrow :) family duties haha. Happy Thanksgiving everyone !
 

Niels B

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Removed the left side point and took some measures with points both open and closed - apparently there was a bad connection somewhere the movable part rotate around the “axle” - surprised me as I would have thought the vulnerable point was where the wire connect. Anyhow - put a new point on and all is good with a nice spark on both side.
So this exercise taught me a lot. Especially check your old coils and your point before you mount them, also tighten the screws that holds the condenser , and last I also found a weak connection between condenser connections to the points.
Once again thanks for all the feedback.
 

arcticXS

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Sounds like you had poor insulation, i.e leakage to ground, on your movable point. Parts that are supposed to be connected, needs to have good continuity all the way, and parts supposed to be well insulated, need to be just that.
 
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