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Discussion Starter · #1 · (Edited)
I had purchased a 72 t120r last year. Boyer micro mk3, minkuni carb & Lucas stator. Positive ground. The bike has never ran correct. It would start fine but breakdown at about 40 percent full throttle. I recently replaced the Lucas 2 wire with a Sparx 3 wire and rectifier, thinking that I had a problem there. Upon unraveling all of the taped wires I founf that the 2 wires from the Lucas were ran to the blk/yel & blk/wht wires on the Boyer black box as well as the rectifier. Could this have damaged the Boyer box. I came up with a really good diagram for the Boyer with a 3 wire system. Re wired the bike correctly, in simplest form, eveything soldered. Now I,m getting no spark. I am assuming that the juice from the stator is AC. Could it have damaged the Boyer. Thanks in advance,Excalibrator
 

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From what I can understand you are saying, your Boyer system wasn't hooked up correctly nor is it now. The Boyer should be in no way be connected to your stator. Your alternator produces an AC current which is converted by your rectifier to DC. Your Boyer gets its power from the battery (DC). The spark timing is created by the magnetic pickup that replaced the mechanical points. I don't think it was a big deal if the yellow and black were cross connected as Boyer fires on every revolution - one spark is wasted on the exhaust stroke.

re cutout at high RPM. You may want to check that your coils are correct. The Boyer prefers 6 volt coils ie less than six ohms total resistance on the primary side of the coils. Since the coils are wired in series, the resistance is the total of all the resistance in all the ignition coils in the system. Stock 12 Volt coils have 3.5 ohms of resistance each, so a twin cylinder bike with two coils has a total
resistance of seven ohms, and a three cylinder bike has a total resistance of 10.5 ohms; both more then the limit of the
Boyer kits. The modification is to install 6 Volt ignition coils, which have a resistance of approximately 1.7 ohms each, so
that the total resistance in a twin is 3.4 ohms, and in a triple is 5.1 ohms, both within the allowed impedence range.
If in your rewiring you inadvertently reversed polarity, your unit is toast.
These links have trouble shooting guides but before going there recheck your wiring:
www.britcycle.com/Manuals/BoyerTroubleShooting.htm
http://www.oldbritts.com/boyer_testing.html
 

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Unless you had the current run through a regulator/rectifier, then yes, the AC will damage the boyer unit. I believe that boyer says that if you run a zener & Rectifier and one fails that it will damage the box. I run a Micro power digital with a tympanium regulator with great results.
I'd contact boyer and ask them about it.
 

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Yes it will be toast. The Boyer units are solid and reliable. They are however made of very small electronic components that do not handle voltage irregularities such as spikes etc. A battery provides a steady 12 volt DC current whereas our alternator puts out an increading current as engine RPM increases. Will it blow? - don't know with 100% certainty. Should it blow? - absolutely.
 
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