Pots 1&4 Intermitant Spark

[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.

[Lynx]

So. I spent the evening in the man cave determined to get to the bottom of this and fix it. Not so . It seems I need to divert my attention to the carbs again! Basically I swapped over all the ignition components but the fault remained on cylinders 1 and 4.

There is still something a bit funny going on with the electrics but I don't think it is the root of the problem now. I can set up the ignition timing spot on, static with a multimeter. Then when I check it with the engine running and a strobe, the marks for 2&3 are still spot on, but the marks for 1&4 are way off . The other thing I noticed was even though the battery is reading at 12 volts, I only have 10 volts at the contact breakers. And still the right set are sparking away madly but the left set have no spark.

So with the bike idling, the engine is knocking like a bastard. Like the carbs are way out or not running on all cylinders. You can hear it cut in now and again intermittently, but if you try to rev up, it is definitely just on 2 cylinders and doesn't want to rev.

I didn't get the carbs off last night but maybe tonight. Those of you who have read my old posts may remember I had a problem with pot 2 when I first got get running. This turned out to be a missing brass ball blocking one of the manufacturing holes. I now wonder if it the same of 1 and 4. I couldn't see with the barbs on the bike but removing or screwing in the pilot air screws made no difference to the running.

[LesterPiglet]

After reading your last post I have no idea why you are thinking carbs. All those electrical anomalies are not due to carbs. Why aren't 1/4 points sparking? Why is your timing off?
Off course it's going to knock firing on only two pots.

[Lynx]

Lester you are right. I was thinking I had swapped over everything ignition. Actally I have not swapped over the contact breakers ! They are pattern parts. Diachi or what ever it is. I though that was a good make. Anyway I'll try some replacements tonight. I think I have some old genuines breakers and condensers still. Hope regenerated !

I've entered the bike in my local vintage show 17-18th May. The organisers insist of all vehicles being road legal. So I need to get it on the road by then.

[Lynx]

She runs again ! The reason there was a problem with the ignition on pots 1&4 was the condenser on the breakers for pots 2&3 was faulty, obviously. There is something very strange going on with my bike. I can set up the ignition timing statically fine. Contact made on the left set of points on the F mark for 1-4, contact made on the right set of points on the F mark for 2-3. And the bike runs fine. Now if I check it with the engine running and a strobe light, the left points are controlling the ignition for 2&3 and the right set control 1&4. Sound like I have the yellow and blue leads the wrong way round. But if I swap them over, the bike will not run, just backfires occasionally. So the ignition timing is obviously way out.

What is going on?

[LesterPiglet]

You need to reverse the yellow/blue wires and also the HT leads. 2/3 to 1/4 and vice versa.

[Lynx]

Well I thought I had . Lester your a star. Sorted. Thanks. Shame the HT leads are cut to match the wrong cylinders.