SOHC.co.uk Forums > CB350/400

Pots 1&4 Intermitant Spark

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Lynx:
The bike had been running fine. I'd taken it for a few test spins around the block. Booked MOT for a couple of Saturdays ago, went to ride it there and it would only start on two cylinders! :'(. Since, I've found a faulty plug cap but it's made no difference and I've fitted a new ignition coil, points and condensers and cleaned out the carbs (again!) and it still isn't running right on 1 and 4. Do the generator windings, regulator or rectifier have ant effect on the spark? I did change them recently for some which seemed to charge the battery better. Also could any of the wiring in the headlight effect this? I did have to remove the headlight to refit the parking bulb, as it had fallen out, the evening before. I have looked in there since but looks OK.

Another thing I just remembered. The points for cylinders 2&3 are sparking quite a lot, whereas I cannot see any sparking on the points for 1&4.

Cheers guys in advance.

Lobo:
Assuming your bike original wiring spec, and going from memory etc as not near my 400F right now. The 'flow of electricity'...

(1) Battery +ve to ignition switch (Red)
(2) Ignition switch to kill switch (Black)  ... and connector likely in the boot under the tank LHS.
(3) Kill switch to coils (a single black / white), and again, not in the headlamp if I recall.
(4) Here the black/white splits to feed the two coils.
(5) Blue from (L) coil down to points, through these & to earth, sparking Cylinders 1/4
(6) Yellow from (R) coil down to points, through these & to earth, sparking cylinders 2/3

Check..
(A) Note 4 above, ie the (L) coil has a good connection to the black / white from the kill switch
(B) The Blue lead out from the (L) coil has continuity all the way down to its set of points... I can't remember where the bullet connector is....
(C) The points (blue set) are correctly assembled... ie insulators / connections as the 'yellow' set.
(D) the points base clean / well earthed to the back plate.

Charging circuit doesn't differentiate between the coils... not a problem here methinks.
Lack of sparking at points does rather suggest a break in notes 4 or 5 perhaps.
. er, good luck.

Simon

Bryanj:
Check the big rubber boot by the brake pedal where the brake light wires go as the points wires connect there and frequently disconnect with moving about

tom400f:
Very simple check - with the points set 1/4 open can you read 12 volts across them? If no meter then use a low wattage bulb.

Lynx:
Thanks for the tips. I'll have a go at it tonight and let you know how I get on. I am suspecting the contact beakers themselves at the moment.

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