Electronic Ignition

[Rob Neal]

The progress on the A65 restoration continues but I've now hit ,yet another, brick wall.  I cannot get the ignition system to spark.  Stripping the motor originally I found a Boyer Bransden ignition fitted along with a single, twin outlet coil.  Checking with the multimeter the coil was toast and the rest of the system looked old along with dodgy connectors.  The original points and adv/ret unit were in the box of bits that came with the bike but had been stored in a damp shed and were corroded to hell.  Thought best to fit a new electronic system as I've had much success with these in the past. It's a Wassel product which was wired up as per the diagram in the photo.  I have checked the continuity of every connector, ensured there's 12+ volts at each connector and that all earths all ground correctly back to battery as you can see by my annotations.  The battery is new and fully charged.  Cranking the motor via the kickstart and the plugs (NGK B7ES) stubbonly refuse to spark.  I've tried alternative plugs and caps to eliminate these as culprits. They are earthed against the cylinder head and a continuity check shows a good ground connection to frame and back to battery.  The coil resistance checks are good.  Low tension 3.5 Ohms, HT 11.8 kOhms. The resistance across the sensor coils on the end of the crank closely match the spec given in the manual at 135 Ohms so they look OK.  I've refitted the connectors too which is why there is insulation temporarily missing in the photo. My local BSA parts chap, Nigel Wynne (Classic Motorcycle Spares) has loaned me a new coil and electronic box to do a substitution check but this also results in zero spark. I've even jury rigged dedicated +ve and earth lines between the various components and battery, bypassing the main loom.  Still no results.  At this point I've bailed out and am enthusiastically investigating the contents of a large wine bottle!  I know it's difficult to advise remotely on a problem like this but is there anything totally obvious I'm failing to see?  Any advice, comment or wine recommendations will be gratefully received.  Rob

[rhyatt]

Across the 2 wires coming from the trigger try this.
You have proved the ohms of the trigger coils , good.

Put your meter onto AC volts and clip across these 2 wires,
Try to use a low scale if you can
Kick over and see if you get an AC pulse being generated, only small maybe 0.5v AC max.
If the trigger is sending this pulse out, then it's not the trigger unit.

[Phaedrus]

Is the rotor correctly mounted?  Hard to tell from the pictures, but if for some reason it's not fully engaging with the stator then the pickups won't generate the required trigger pulse.

[cdsdorset2]

There  seems to be a few people having problems with these units. Am i imagining a pattern of a certain supplier bringing out producs that  initially looks very good but then quality issues start to appear?

[Rob Neal]

Ryhatt & Phaedrus.  Thanks for the advice.  The rotor mounting looks ok as it rotates concentrically. i.e. it doesn't wobble and , as far as I can tell rotates equidistant between the static pick ups.  The AC reading is about 0.6V which suggests that the trigger coils are OK and the unit is generating a trigger signal correctly.  This eliminates the trigger as the possible cause of the problem which is a positive result. 

As for the quality of the product, I'm inclined to think that there shouldn't be a generic problem as I've already carried out the 'substitution' checks using new parts. Also Nigel of Classic Motorcycle Spares has fitted the Wassel system to many of his customers bikes without any issues.

It MUST be an earthing fault somewhere that I'm just not tracking down at the moment.  I'll continue to persevere and let you know once I've managed to electrocute myself via a lively spark plug!

As ever guys, thanks for taking the time to help out, much appreciated.  Regards. Rob.

[rhyatt]

Some double output coils need both plugs earthed out to function.
Is your bike the same polarity earth as the unit demands ie pos etc or neg etc.
But you've subd the coils.

Remember, the black box only does what the points used to do ie earth the primary side of the coil, thereby charging it up and then, when the trigger pulse comes  breaking that earth path the same as the points opening.
This breaking collapses the primary and induces the ht in the secondary.

I just looked at the Wassell site - for a twin cylinder bike , shouldn't you have used 2 x 6v ignition coils wired in series as shown on that diagram ??

any HT coil , car or bike , 6 or 12v has the voltage enetring the coil via the primary +ve and going to earth via the -ve(thus charging the primary)

when the points open(or box switches) the collapsing magnetism induces the HT voltage in the secondary windings which spark via the plug lead to earth(the same earth as the points switch on and off thereby completing the HT path

some twin output coils are wired differently internally

https://burtonbikebits.net/bbb/wp-content/uploads/2019/03/WW61495.pdf

[pbucks]

Having just gone through this, but with a pazon system the most usefull piece of advice I can give, is get a pair of spark indicators like these https://www.amazon.co.uk/Sealey-SEAQF-VS526-Ignition-Multicoloured/dp/B00S6C94VA/ref=pd_lpo_sccl_1/259-8843024-1311721?pd_rd_i=B00S6C94VA&psc=1
I'd never used them untill my mate gave me a pair to try, but I wouldn't be without them now.

[Dean Southall]

On some electronic ignition systems the spark can be of such short duration that its difficult to see.
I also use the spark indicators referred to above and find them very helpful.

[Rob Neal]

I've not used spark detectors before but have ordered a pair.  If that doesn't show anything then I'll buy a pair of 6V coils.  Any specific type/recommendation for use with the Wassel kit or will any generic type be OK?  Thanks everyone. Rob

[rhyatt]

I'm not sure, but if you have a 12v single output coil in your spares box then try that.
If that sparks then you know the box is switching fine

[Rob Neal]

Thanks for suggesting the spark detector.  I ordered one which arrived today and it shows that there is indeed a spark. That's a relief!  Advice, as always very much appreciated.  I can now get on and try and fix the speedo drive leak from beneath the timing chest.  There's always something to keep us busy with these old bikes!  Rob