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BSA B40 No Spark


evo boy
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Contact breakers could be stuck open or badly corroded so no earth path created. Ignition coil could have internal short. Wires may have corroded through. HT lead may be faulty, including the plug cap breaking down electrically. Can you not ask your Dad if he knows if it has electronic ignition, apologies if that’s no longer possible. How are you testing the HT spark, remove the plug cap, make sure you camp see wire in the end of the HT lead, hold this end about 2-3mm front a cylinder head fin, get someone to kick the engine over, there should be a nice bright blue flashseen between the lead and fin. Does this B40 have a ‘kill switch’ this could be in the off position or corroded up. Next check the wires to the ignition coil, if they feel hard and stiff they may not be acting as a wire anymore. Some trials bikes of that era were modified to run with a small battery, doing away with the heavy generator, so if that’s the case you will need a good 6 volt battery. Some B40’s and similar C15 models had the contact breakers in small distributors that were mounted into the crankcases, other later models had the contacts etc mounted in the side case beneath a round cover. With the contact breakers you need to establish that the shaft in the distributor goes round when cranking the engine. You need to ensure there is an operating gap between the fixed base contact and the pivoting part of the contact breaker assembly. Hold open the contacts and look at each contacts surface, clean with a piece of wet and dry rubbing down paper or a board type nail file, aim to produce a cleanish face to each contact. You can connect a torch bulb and two wires to the contacts to see if they work as an on and off switch, or use a voltmeter set to continuity. If all is well then the condenser may be faulty, actually a capacitor. With a duff condenser you can still get a spark but it will be very weak. There are some useful videos that show all of this on the net. The coil can be tested for continuity, but I’ll refer you to the demo videos for this, take me too long to explain. Hope this is helpful ?

 

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On 10/09/2018 at 8:05 PM, jon v8 said:

No B40's were fitted with electronic ignition from new,so if it has it fitted it will be an aftermarket setup.Take some pics of it and post them up so we can id it.

Thanks for that I spoke to my Dad and he said it's has boyer bransden electronic ignition on it so I don't know if anyone can help?

 

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  • 4 months later...
 
 
 
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18 minutes ago, evo boy said:

Thank for that!! So just normal unleaded then? As I was told it should be old leaded Petrol but I can't get it anywhere.

Thanks

No wonder, lead in petrol was banned nearly twenty years ago.  It was better stuff though (for vehicles anyway) - someone dragged a Scorpa out the shed recently and it fired up second kick on what had been lying in the tank.

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2 hours ago, 2stroke4stroke said:

No wonder, lead in petrol was banned nearly twenty years ago.  It was better stuff though (for vehicles anyway) - someone dragged a Scorpa out the shed recently and it fired up second kick on what had been lying in the tank.

The fuel then was stable and would keep for quite a long time without ‘going off’ or going stale or destroying everything it came into contact with....bit like an MP with initials JC.

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Hello all needs some mote help with my no spark. Could anyone tell me what the black square box is in my picture? Also I'm trying to test the magneto part what reading should I be getting? I'm looking at the point what should they be set to?

Many thanks

15498850466533037035276882996484.jpg

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10 minutes ago, b40rt said:

You said you had boyer ignition ?  Sounds like a standard set up to me. Black things a rectifier, blue a condenser. 

Hello b40rt thanks for the reply that's what I was told by my Dad but think your right. You wouldn't know what the points should be set to? 

Many thanks

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