No Spark at Boyer Brandsen box

I just joined the group and looking forward to Norton discussions! I have a 1973 850 Commando. After a ride yesterday I took off the gas tank and spent some time getting the choke and carb control cables better routed under the tank. Doing so, I disconnected the connections on the right side coil. There were two connections to the coil and one to frame/ground. After getting things better arranged I reconnected the wires (In what I remembered as the right spots - basically following the "memory" of the wires and how they naturally bent). I put the tank back on, connected fuel lines and expected the usual engine start in one or two kicks. Instead, nothing. I took the tank back off and began inspecting my wires and I noticed the Boyer-Brandsen module box to be extremely hot.

Since yesterday I have been following the troubleshooting procedures from Boyer Brandsen - I have no spark at all. The troubleshooting sheet indicates that I am at the point where either one or both of the coils failed or the BB box is bad. So my question is does anyone have experience with the BB box going bad? Did the box get overheated and damage it? If so any ideas on why the box failed? Or should I be looking at the coils?
Looking forward to some sage advice.
Regards,
lloyds-son

Welcome to the forum.

lloyds-son said:

There were two connections to the coil and one to frame/ground. After getting things better arranged I reconnected the wires (In what I remembered as the right spots - basically following the "memory" of the wires and how they naturally bent). I put the tank back on, connected fuel lines and expected the usual engine start in one or two kicks. Instead, nothing. I took the tank back off and began inspecting my wires and I noticed the Boyer-Brandsen module box to be extremely hot.

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First I suggest you make absolutely sure you have re-connected the coil wires correctly in accordance with the Boyer Bransden instruction sheet wiring diagram if you haven't already done so (the coil terminals should be marked (+ & -). http://www.boyerbransden.com/pdf/KIT000 ... 00017_.pdf
(That's assuming your Commando hasn't been converted to negative earth/ground?)

lloyds-son said:

Since yesterday I have been following the troubleshooting procedures from Boyer Brandsen - I have no spark at all. The troubleshooting sheet indicates that I am at the point where either one or both of the coils failed or the BB box is bad.

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It's unlikely that both coils are going to fail at exactly the same time, however if the the wires had been reconnected incorrectly then that certainly could have damaged the Boyer box.

http://www.tioc.org/boyertest.htm

Thanks. I believe I mis connected wires - which is why the box got so hot. Looks like I need to get a new box.

Ouch.

Welcome to the forum.

I am so NOT smart when it comes to electrical stuff I learned a long time ago to mark every wire I disconnect first, take pictures and make notes of how it all was before I take anything apart. One picture taken before you pulled the wires could have prevented this. Sorry, I don't mean to make you feel worse. Just trying to stress how being overly safe can't hurt. Please keep us up on what you do to fix this. I worry about what I would / will do when my Boyer eventualy goes. What is the life span for one anyway? Mine must be 20 years old.

gtsun said:

I worry about what I would / will do when my Boyer eventualy goes. What is the life span for one anyway? Mine must be 20 years old.

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19 yrs.




:mrgreen:

Your box may still be serviceable.

If you've re-connected things according to the wiring diagram you can put a voltmeter lead on the negative black wire running from the box to the lead coil at the coil terminal and kick the engine through with the ignition on. If the voltage fluctuates between 0-10 volts or so when kicking through the box is switching satisfactorily.

Over a twenty-year period I've had bad coils about three times as frequently as bad Boyer boxes--with battery voltage above 12V and a good rotor, stator, coils and wiring it's a pretty bulletproof system--good luck


Tim Kraakevik
kraakevik@voyager.net

I bought a new box and connected everything, I soldering in 2 or 3 new quick connect plugs and viola, the bike started. I went through the timing set-up but it seems like it is not running as smooth as I would like. It kinda surges at a steady cruise. Great power and smooth steady acceleration but kinda funny at steady speed.
I am thinking I should go back and adjust the timing - Boyer instructions have advance at 31 degrees, the shop manual says it should be 28 degrees - of course that is with point system. Anyone have a thought here? I figure I should just run a couple of quick checks and rotate the contact plate a little forward to see if that helps, if not retard it some to see if that is the way to go.

Hi,

31 is the number, set it as per the instructions then adjust with a timing light.

28 was the magic number with points and condensors.

lloyds-son said:

It kinda surges at a steady cruise. Great power and smooth steady acceleration but kinda funny at steady speed.
I am thinking I should go back and adjust the timing - Anyone have a thought here? I figure I should just run a couple of quick checks and rotate the contact plate a little forward to see if that helps, if not retard it some to see if that is the way to go.

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Timing is not the cause of the surging - it is most likely to be carbs, too rich at mid-throttle. Assuming it has Amal Concentrics - Try dropping the needles down 1 notch and identify the main jet size (marked in small numerals). It should be around 260 or 280.

Mick

I have had a Boyer fail from a poor corroded ground so clean that up too. Surging is carbeuration for sure,check your cables for lubrication and smooth routing to carbs too. Peter.

Good direction - thank you!