SOHC.co.uk Forums > CB500/550
Fuse box woes
alexdecker:
Alright, took the fuse box off and apart, and someone had rewired the whole thing in reverse. So I put the 7A in the 15A spot and the 15A in the 7A. I don’t know if this has anything to do with the spark in 1 and 4 or the hi beam, but at least I fixed that now.
K2-K6:
"I also don’t have spark in 1 and 4. I have power at the coils, at B/Y coming out of the coils and at B/Y at the points plate (tested by disconnecting them from the plate and measuring). I have also tested all the spark plugs, and they are all giving blue sparks. Just only in 2 and 3.
Any ideas?"
The points are switching the earth circuit and not as many visualise the positive voltage. Conceptually (with them closed) it's a bit like having a plug in a bathtub, the coils fill up with energy from positive feed all the time the earth is established, removing the earth causes the coils to discharge out through the plugs the energy that's been stored.
Unplug the points, put continuity metering on the points wire (not the coil wire) and check it across to the crankcase as it should have continuous route with points closed. When the points open that continuity MUST be broken. If it doesn't do this the coils will never discharge a spark.
Check that firstly to see if those points are fulfilling that function before moving onward.
alexdecker:
--- Quote from: K2-K6 on July 29, 2022, 04:58:00 PM ---"I also don’t have spark in 1 and 4. I have power at the coils, at B/Y coming out of the coils and at B/Y at the points plate (tested by disconnecting them from the plate and measuring). I have also tested all the spark plugs, and they are all giving blue sparks. Just only in 2 and 3.
Any ideas?"
The points are switching the earth circuit and not as many visualise the positive voltage. Conceptually (with them closed) it's a bit like having a plug in a bathtub, the coils fill up with energy from positive feed all the time the earth is established, removing the earth causes the coils to discharge out through the plugs the energy that's been stored.
Unplug the points, put continuity metering on the points wire (not the coil wire) and check it across to the crankcase as it should have continuous route with points closed. When the points open that continuity MUST be broken. If it doesn't do this the coils will never discharge a spark.
Check that firstly to see if those points are fulfilling that function before moving onward.
--- End quote ---
Unplugging the points and measuring them from the wire harness and grounded to the crankcase, I get continuity on both points when they are closed.
K2-K6:
And what do you get when the points are open ?
You should loose continuity as soon as the contact faces move away from each other, this is what initiates the spark to come from the coils.
Effectively two states, continuity fills the coils ready to spark, breaking the continuity makes the stored energy exit down the HT leads.
alexdecker:
--- Quote from: K2-K6 on July 29, 2022, 06:32:11 PM ---And what do you get when the points are open ?
You should loose continuity as soon as the contact faces move away from each other, this is what initiates the spark to come from the coils.
Effectively two states, continuity fills the coils ready to spark, breaking the continuity makes the stored energy exit down the HT leads.
--- End quote ---
When the points are open, I don’t have continuity! So that should be good, right?
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