SOHC.co.uk Forums > CB750
No Spark
Saesneg Shaun:
I checked the static timing and points. It all seems fine but I slackened them off and set them again and it now runs on 1 & 4.
Curious as i'd not touched the points since i've owned the bike but it runs, sort of!
2 & 3 still not sparking though. Its quite hard to set them as the centre cam that the points run off is really slack and can be rattled about on the shaft. I'm guessing it isn't supposed to be like that
Saesneg Shaun:
--- Quote from: Oddjob on May 04, 2022, 03:01:16 PM ---Also check the connections on the block connector the fuse box connects with. It's possible they were the fault in the first place and it was them failing and connecting with something it shouldn't that caused the fuse to blow.
--- End quote ---
Could be. I did find a bodged wire soldered between the back of the 15A fuse holder and the brown/white wire from the ignition switch, gawd knows why as the original wire seems fine!
K2-K6:
Normally it wouldn't be rattling around, likely part of the problem for you.
Not hard to take apart, undo 10mm nut in centre, lift off the large "crank" nut, undo the securing screws that hold the whole points plate on and you can swing that out the way.
Then the cam (advance retard mech) can just be pulled off to look at it. It's got a location pin on rear so you can put it back in same place. Low risk to check it out and see if anything is out of place.
Oggers:
A slack cam is no good at all! ATU weights should move out freely, springs free of any crud. Oil the pivot points perhaps. Also check out all screws holding points for 2 and 3 are tight, and re-check the gap. Clean the points. Check out all electrical connections to 2 and 3 points and check out the condensor - with ignition on and if it sparks when you open the points gap, then a possible condensor problem. Have you a spark across the points when it turns over?
Saesneg Shaun:
--- Quote from: Oggers on May 05, 2022, 02:51:18 PM ---A slack cam is no good at all! ATU weights should move out freely, springs free of any crud. Oil the pivot points perhaps. Also check out all screws holding points for 2 and 3 are tight, and re-check the gap. Clean the points. Check out all electrical connections to 2 and 3 points and check out the condensor - with ignition on and if it sparks when you open the points gap, then a possible condensor problem. Have you a spark across the points when it turns over?
--- End quote ---
I can get it to fire but only on 1-4. I have checked the (new) spark plugs and 2-3 ins't sparking.
With 1-4 F mark lined up and the points gap set to 0.4mm the points don't break the circuit within the timing slots on the base plate.
Also I seem to have a problem where the points arm touches the cam as it doesn't look like the little contact arms touch the cam at its lowest point?
The cam nut wasn't tight but wiggle on the cam was just end float so that seems ok.
I don't get this, she's always been a sod to start but was running ok until the main fuse blew?
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version