Topic: 400/4 Electronic Ign.

[patlac]

 Hi I want to replace the coils on my 400/4 with coils from a 750/4.Is this OK? The Bike is fitted with Boyer Micro Mk 111 system.The coils on 400 are moulded the 750 ones are not.I wired them up as follows. Blu and Yel from Transistor marked Stator to Bike Blu and Yel.Black power to Blk/white Blk marked to Batt neg the coil wires Blu and Yel connected Yel neg Coil 2-3 Blu to Pos Coil1-4 and looped 2-3 pos to 1-4 neg. Doing this I have no Spark (It was Sparking on original coils) What am I doing wrong.  NOTE I fitteg new Ign leads and plugs.

[raymond10078]

The instructions show the Yellow (from transistor) going to Yellow (of coil - negative lead).  The Blue (from transistor) going to Blue (of coil - negative lead).  The coil positives are tied together (and head off to the bikes emergency kill switch).  The coil positives (I recall them as Black wires with white tracing) get power all of the time (when the key is ON, and the kill switch is set to ON).  The transistor box just connects the coil negatives to ground when pulsed by the stator.

[Bodi]

I tried to understand your explanation of how you wired this but my head hurts and it still doesn't make sense.
Kandrtech is right. One wire from each coil goes to the black harness wire. The other wires from the coils connect, one each, to the wires from the transistor ignition. There's no looping.
That should get you a spark.
It might not actually run though, the coil wires may be reversed so if not try swapping around the wires from the ignition box to the coils.
I'm not sure about the BB system but most ignition boxes connect this way.

[patlac]

Ok Lads I will try your recommendation hopeing I dont fry the Transistor box. What is recommended is Yellow from Trans Box to Neg on 1 coil Blu from Trans box to Neg on other coil, and 2 Pos on coils to Blk/White. (Supply)

[TwoTired]

The coils on 400 are moulded the 750 ones are not.

I do know that stock 750 coils also have molded in coil wires.  If yours aren't molded, they aren't stock.  And, none of us knows what you actually have to wire up.  We can only guess.

Cheers,

[dave500]

go over your install,be sure to run the black box earth directly to the battery,check the fuse incase youve had a hiccup,heres a genuine diagram if you dont have one,,im using a mk3 on one bike and the later digital on another and i like these units,youll need a timing light to set it up,if the rotor is a little out youll get no spark also,the mk3 and digital have a different rotor install spec but share the same parts except for the box.if you havent fitted the boyer from scratch the coils should work,assuming it ran before hand?

[patlac]

Thank you ,Thats very helpful  I have wired up per your diagram and have a Spark but bike would not start. I will have a go at the timeing on Monday so Fingers crossed all will be ok. I have a Strobe to finally set up. I will be back with results

[patlac]

 I would like to thank all who gave me advice on my problem I fitted 750/4 coils and  timed the Ignition  Ran engine used Strobe For final set up. Took bike on a 30mile run and all went well. as we say here Fair Play to you.

[dave500]

no worries.