airhead Ignition Control Unit ( ICU)

Discussion in 'Airheads' started by a_bakla, Oct 30, 2012.

  1. a_bakla

    a_bakla A&F

    Oct 28, 2009
    My G/S runs with an ICU different than the stock one.I think bike previous owner changed it. I ve searched that what is it? İt is russian car Lada's igniton control unit????.I've found specs of this unit. (3620.3734)

    <TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD width="89%" bgColor=#ffffff>Range of operating temperatures, °&#1057;</TD><TD width=1 bgColor=#000000 rowSpan=8>[​IMG]</TD><TD width="11%" bgColor=#ffffff>
    -40 .. +85

    <TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD width="89%" bgColor=#f2f2f2>Nominal supply voltage, V </TD><TD width="11%" bgColor=#f2f2f2>

    </TD></TR></TBODY></TABLE><TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD width="89%" bgColor=#ffffff>Permissible limits of supply voltage, V </TD><TD width="11%" bgColor=#ffffff>
    6,0 .. 18,0

    </TD></TR></TBODY></TABLE><TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD width=3 bgColor=#f2f2f2></TD><TD width="89%" bgColor=#f2f2f2>Range of an uninterrupted spark formation, rpm of the crankshaft of the 4-cycle 4-cylinder engine</TD><TD width="11%" bgColor=#f2f2f2>
    20 .. 7000

    </TD></TR></TBODY></TABLE><TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD width="89%" bgColor=#ffffff>Commutating current, &#1040;</TD><TD width="11%" bgColor=#ffffff>
    7,5 ± 0,2

    </TD></TR></TBODY></TABLE><TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD width="89%" bgColor=#f2f2f2>Time of a sparkless cutoff of a collector current, sec</TD><TD width="11%" bgColor=#f2f2f2>
    1 .. 2

    </TD></TR></TBODY></TABLE><TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD width="89%" bgColor=#ffffff>Maximum allowable influence of the increased supply voltage up to 5 min. at the spark formation frequence more than 200 Hz (6000 rpm of the crankshaft of the 4-cycle 4-cylinder engine), V</TD><TD width="11%" bgColor=#ffffff>

    </TD></TR></TBODY></TABLE><TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD width="89%" bgColor=#f2f2f2>Maximum allowable pulse overvoltages of a positive and negative polarity, V </TD><TD width="11%" bgColor=#f2f2f2>


    And schematics is there :

    I wonder is this unit suitable for an airhead ?
    I am planing to convert my g/s to twin spark.I ve already drilled the heads and and searching for second ICU and coil.
    This unit is very easy to get and cheap (10$). Can I use this unit or is it better to get stock black ones?
  2. Rob Farmer

    Rob Farmer Long timer

    Aug 27, 2002
    Loughborough, Leicestershire. England
    With the exception of the kickstart icu the ignition modules are the same as dozens of European cars from the 80s and 90s including Porsche. The most common variant is a Lucas dab400
  3. boxerboy81

    boxerboy81 Stay Horizontal

    Jul 22, 2009
    Melbourne, Oz
    Not sure they're quite the same over the years. There were a few updates finishing with the turquoise lettered one being the last and covered all predecessors. Other versions may work, but they may not be the same despite appearances.

    The turquoise lettered ICU
    pn 12-14-2-325-284 with riveted heat sink instead of small bolts is the last one made by BMW. The heat sink is integral and doesn't require periodic servicing of heat sink paste. It has the latest updates and works for bikes with a kicker or not.
  4. chasbmw

    chasbmw Long timer

    Feb 19, 2006
    Bath Uk
    You need a second coil, but I don't think that you need a second ICU.
  5. supershaft

    supershaft because I can

    Sep 9, 2010
    San Francisco Bay area
    ICU's are not all the same. The torquoise ICU's from BMW can take lower coil primary resistance. Tha'ts the main spec to deal with regarding ICU's which I can't ascertain from those specs. The rev limit is too low as well if it matters? Run the same primary resistance as what the ICU was originally run with or a little higher but never lower. That will fry the ICU. Too high Primary resistance can weaken high rpm spark from what I have read although I haven't found this out for myself. I HAVE found out about matching ICU's to too low primary resistance myself!

    I am running two .7 ohm dyna's on my dual plugged stock bean can with the weight stops bent in to restrict full advance. It is running good!
  6. motu

    motu Loose Pre Unit

    Dec 28, 2001
    New Zealand
    The Lada Samara uses the BIM 137, it's used in a lot of after market ignition systems because it adjusts dwell. It's the same case as the airhead module - you'd need to see a diagram of the pins to know if it relates to the one on airheads. Worth a try on someone else's bike.