boyer bransden help! norton 850

hey team - still a tad new to nortons and always appreciate your kind support....


been working pretty hard on a 90% custom chop...the guy i got the pile of parts from included a boyer bransden kit - but with a dyna 3ohm dual output harley coil....

my question for you guys is a) is everything i need seen in the pic?

and b) prior to reassembling the engine, i was under the impression both cylinders would fire in parallel...but after putting the head it was clear they operate 180deg apart (right?) so...my question is - with this coil supplying spark to both plugs - and having only two contacts - how does it know to alternate spark? or does it send spark to both plugs at TDC each time? just anticipating mixing up the HT leads during install this week....

and finally c) is there a strong preference for anyone to either go positive or negative ground? i am naturally inclined to go negative ground - but for some reason brasden seams to gravitate to pos. ground.....?


any other tips would be kindly received....

ill be making my own wiring harness as well....


http://i1281.photobucket.com/albums/a51 ... 668dd4.jpg

ianfotheringham said:

b) prior to reassembling the engine, i was under the impression both cylinders would fire in parallel...but after putting the head it was clear they operate 180deg apart (right?)

so...my question is - with this coil supplying spark to both plugs - and having only two contacts - how does it know to alternate spark? or does it send spark to both plugs at TDC each time? just anticipating mixing up the HT leads during install this week....

Click to expand...

Both cylinders (should) rise and fall together.

The Boyer pickup rotates at half the speed of the crankshaft therefore the Boyer provides sparks (to both cylinders) every 360 degrees of crankshaft rotation. Alternately, one cylinder will be on it's compression stroke, and the other on its exhaust stroke, thus one spark is used and the other is wasted each time.

ianfotheringham said:

a) is everything i need seen in the pic?

Click to expand...

Yes, basically it's all there, plus a Powerbox which is a regulator/rectifier, and not part of the ignition system.

ah ha! figured that must be it....thanks for the clarification!

Here are the fitting instructions, just in case you need them: http://www.boyerbransden.com/pdf/KIT000 ... 00017_.pdf

also wondering if anyone else out there is using the battery eliminator thing? thoughts? .... im concerned there wont be enough juice on a single kick to get the spark going.....

ianfotheringham said:

but for some reason brasden seams to gravitate to pos. ground.....?

Click to expand...

I think that's only because the original system is positive ground.

ianfotheringham said:

also wondering if anyone else out there is using the battery eliminator thing? thoughts? .... im concerned there wont be enough juice on a single kick to get the spark going.....

Click to expand...

The Powerbox should contain a capacitor (unless it's an old one) so it should allow batteryless running if you can get enough output to fire the Boyer MkIII unit.

http://www.boyerbransden.com/PBdynamo.html