SOHC.co.uk Forums > CB750
No Spark
K2-K6:
Quick reality check, swap the two wires over coming from coils to points and see if the 2/3 coil fires then. It won't run at all but will show (with confirmed switching from the 1/4 points, if the 2/3 coil will make a spark) and which part of the system is working.
It sounds like the small rod that secures the points cam may be bent. As my routine above, strip the points plate and advance mech, then spin the motor to see if the rod is bent (if so it can give all sorts of errors in points gap) and at least give a baseline to work from.
Saesneg Shaun:
--- Quote from: K2-K6 on May 05, 2022, 03:44:04 PM ---Quick reality check, swap the two wires over coming from coils to points and see if the 2/3 coil fires then. It won't run at all but will show (with confirmed switching from the 1/4 points, if the 2/3 coil will make a spark) and which part of the system is working.
It sounds like the small rod that secures the points cam may be bent. As my routine above, strip the points plate and advance mech, then spin the motor to see if the rod is bent (if so it can give all sorts of errors in points gap) and at least give a baseline to work from.
--- End quote ---
Haven't swap the leads yet but i'm not so sure about the points cam now. The centre shaft runs true ish but theres lots of play in the whole assembly?
Couple of vids attatched
https://youtube.com/shorts/uI7pr4SpOKE?feature=share
https://youtube.com/shorts/wGs-SIJDHKI?feature=share
K2-K6:
Definitely something wrong with securing the advance mech there.
Agree the rod looks reasonably ok, but mech shouldn't be moving like that and with any real slack at all.
You'll get no real accuracy in timing, gap and dwell to set it up correctly. Should have a washer under the six mm nut to secure the bigger nut, is there anything there ?
Saesneg Shaun:
--- Quote from: K2-K6 on May 05, 2022, 04:29:01 PM ---Definitely something wrong with securing the advance mech there.
Agree the rod looks reasonably ok, but mech shouldn't be moving like that and with any real slack at all.
You'll get no real accuracy in timing, gap and dwell to set it up correctly. Should have a washer under the six mm nut to secure the bigger nut, is there anything there ?
--- End quote ---
Yes there is. The play is there with everything nipped up but not stupidly tight. When I stripped it down the 10mm nut was barely hand tight.
K2-K6:
Wondering if the rod is backing out of the crank which will release the advance mech ?
If that's happening, then the securing nut may be reaching thread end before tightening mech properly.
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