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Thread: M900 replacement ignition pick up failing as revs. rise ?

  1. #1
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    Default M900 replacement ignition pick up failing as revs. rise ?

    Dear All,

    Have replaced the front cylinder ignition pick up (open circuit) of a 1973 M900 with an Electrex P8 with sparks now restored however, the spark gradually deteriorates to zero as the revs. rise, pick up gap to the flywheel triggering lug set to 0.025ins. to be the same as that of the rear cylinder.

    Any one out there experienced this ?

    I cannot call Electrex for their advice at the moment as out on the hills with the Argocat weekdays and hence well clear of any mobile reception.


    Any advice gratefully received.

  2. #2
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    I haven't experienced that problem myself. If you swap round the ignition modules and the coils which is easy enough and the problem still persists then it can only be the pick up. Swapping the pick ups is a bit o'a trachle but if the fault moves to the other cylinder it would confirm it.

    Old enough to know better, young enough not to care

  3. #3
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    Was there not a post on here a year or so ago regarding Electrex world's pickup's suggested wiring being incorrect? The postee had access to an oscilloscope to check and was able to rectify and correct the way around
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  4. #4
    Join Date
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    Good memory Sam, yes there was. If I remember correctly the wires were marked the wrong way round. This would cause a phase reversal of the pick up pulse so that the ignition unit triggers off the wrong edge of the pulse. But this doesn't stop the spark.
    I experienced this last year working on another forum member's project bike. One of pickups was wired the wrong way round which advanced the spark by the pulse width. The bike would start and idle but any attempt at opening the throttle resulted in pops and bangs and it would cut out on the affected cylinder because the spark was far too advanced.

    Old enough to know better, young enough not to care

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