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  1. #1

    Join Date
    Oct 2018
    Posts
    5

    Default cb650 Coils 2&3 not firing.

    Looking for any tips here:

    83 Honda cb650sc that will NOT turn over, just chugs. The coils are both good, test read fine. Connections are clean, plugs will foul pretty quick. Carbs 1 & 4 are popping, trying to fire, I get get heat from them. Some poofs of air out of 2 & 3, no heat. Tried different plug wires too. Carbs themselves are clean.

    Any suggestions on what I might have missed? I have a week left to get this running.

  2. #2
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    Join Date
    Apr 2013
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    Compression test all four. Verify ignition timing and that the wires are on the correct plugs.

    What does "the carbs look good" mean? If the bike sat a while it's highly likely to need carb work. That is so normal (I've done countless customer bikes) given your symptoms I'd pull and dip or ultrasonically clean them.

    plugs will foul pretty quick
    Fuel or oil? Post pics.
    Last edited by farmall; 08-12-2019 at 2:23 PM.

  3. #3

    Join Date
    Oct 2018
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    I had great compression on all 4. Carb bowls/jets cleaned, new gaskets. Wires are on the right plugs. I will look at the ignition timing!

  4. #4
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    Carb bowls/jets cleaned
    By what method? Details matter.

    Tell us what history you know on the bike. Do you KNOW it ran when parked?

  5. #5
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    Did you check the clearance for the pulser coils?
    Found this:
    The pulser clearance should be 0.012 - 0.016 in or (0.3-0.4 mm).

    A short inside pickup coil windings may also weaken the signal and cause problems like yours but first check the cabling between pickup coils and spark units/ ignitors. The pickups can be tested separately, their resistance should be 530 Ohms 50 Ohms at 20C between both blue (for 1-4) and both yellow cables (for 2-3), respectively.

    A proven procedure to get happy is to exchange 1-4 vs. 2-3 ignition circuit components until you know which one causes the trouble by shifting the problem from 1-4 to 2-3.

    The CB650s have a transistorized Kettering system.
    In other words, we have transistors/pulse triggers that replaced the points.

    With the Kettering Induction ignition design, the coils are powered all the time at 12 volts and are commanded to collapse to spark by the ignition module. Here, the ignition module disconnects the primary winding coil ground. The coil secondary winding collapses to spark at about 30,000 volts.

    Read a bunch more with links here:
    CB650 Ignition
    http://hondacb650.com/viewtopic.php?t=488

    and look here:

    Honda CB650 Manual
    "Electrics"
    Ignition System
    Click image for larger version. 

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    http://cosky1.tripod.com/id1.html

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