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  1. #1
    CB750 New Member thesulman's Avatar
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    VERY WEAK SPARK TO 2+3 CYL's

    I have 79 750F cyl's 2+3 won't light a timing lite, but when I ground the plug on head I get a weak spark, cyl's 1+4 are just fine. I've changed coil, switched the spark units, pulse gen tests fine, 514 ohms on yellow wires and 516 on blue wires. I even got a different pulse gen and put it in still the same 2+3 won't light a timing lite. Iswitched the blue wire to the 1+4 cyl coil over to the 2+3 coil and wala it lites up the timing lite hooked up to 2+3. It appears to be a problem with the yellow wire that goes to the 2+3 coil. I have continuity down to the connection that goes to the spark unit.

    I'm to the point that I just go out to my garage drink a beer and just look at it. I need help! Sulman

  2. #2
    Moderator dirtdigger's Avatar
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    If I was you I would bypass the wire with a new wire...sounds like you have done some troubleshooting to the point where I would say it may be a wire issue. Continuity does not mean it will carry current, a sing strand of wire will still show continuity but wont carry any current.

  3. #3
    CB750 New Member lordworm's Avatar
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    Same or similar problem

    Quote Originally Posted by thesulman View Post
    I have 79 750F cyl's 2+3 won't light a timing lite, but when I ground the plug on head I get a weak spark, cyl's 1+4 are just fine. I've changed coil, switched the spark units, pulse gen tests fine, 514 ohms on yellow wires and 516 on blue wires. I even got a different pulse gen and put it in still the same 2+3 won't light a timing lite. Iswitched the blue wire to the 1+4 cyl coil over to the 2+3 coil and wala it lites up the timing lite hooked up to 2+3. It appears to be a problem with the yellow wire that goes to the 2+3 coil. I have continuity down to the connection that goes to the spark unit.

    I'm to the point that I just go out to my garage drink a beer and just look at it. I need help! Sulman
    Hey I am having the same problem, but 2-3 die only once the bike is warmed up. So I have all four working until about 10min of riding and bam, 2-3 go out and the rest of my commute is on the 1-4 cyl.

    It is certainly an electrical issue, since the coil isn't sending a spark when its happening. Did you happen to find a solution?

  4. #4
    K2750tracy K2750tracy's Avatar
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    Quote Originally Posted by lordworm View Post
    Hey I am having the same problem, but 2-3 die only once the bike is warmed up. So I have all four working until about 10min of riding and bam, 2-3 go out and the rest of my commute is on the 1-4 cyl.

    It is certainly an electrical issue, since the coil isn't sending a spark when its happening. Did you happen to find a solution?
    Your issue sounds like the 2-3 coil is breaking down once it get hot, very common on older coils. Replace the coil.
    old Honda junkie

  5. #5
    CB750 New Member lordworm's Avatar
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    Quote Originally Posted by K2750tracy View Post
    Your issue sounds like the 2-3 coil is breaking down once it get hot, very common on older coils. Replace the coil.
    Replacing the coils were the first thing I did, I've even rotated them to see if the problem moves to the other cylinders, and it didnt.

    The problem is that there is no spark even coming up to the coil

  6. #6
    K2750tracy K2750tracy's Avatar
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    Well then you need to look further back the system. The next component back is the spark modules, switch them see if you problem follows. then the wiring down to the ignition system. Process of elimnation.
    old Honda junkie

  7. #7
    CB750 Enthusiast mchapa's Avatar
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    Do you have the Dynatek, dyna s system ???? One of my pickup coils was going bad after it got hot ...about 10 to 15 minutes...
    I yanked the dynas s out and replaced with stock points..... and haven't had a problem ever since....

  8. #8
    CB750 Member Rkrutledge's Avatar
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    I am having a similar issue. with my 81 C. The PO put on a Dyna 2000. I am no longer getting spark to the the 2-3 coil. I have replaced the coil, wire, plugs, and battery. I am looking at my options for spark units. Thinking about going to the procomeng spark unit for cost effectiveness.

    http://www.procomeng.com/estore/feat...c-mh900-a.html .

    Mchapa what was your experience changing back to OEM?

  9. #9
    CB750 Member Rkrutledge's Avatar
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    Or does anyone have experience ricks motors sports.

    http://www.bikebandit.com/aftermarke...i-box?m=151804

    I am just looking for options.

  10. #10
    CB750 Enthusiast mchapa's Avatar
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    Quote Originally Posted by Rkrutledge View Post
    I am having a similar issue. with my 81 C. The PO put on a Dyna 2000. I am no longer getting spark to the the 2-3 coil. I have replaced the coil, wire, plugs, and battery. I am looking at my options for spark units. Thinking about going to the procomeng spark unit for cost effectiveness.

    http://www.procomeng.com/estore/feat...c-mh900-a.html .

    Mchapa what was your experience changing back to OEM?
    It works great....adjusted once a year....the original stuff last a long time....

  11. #11
    CB750 Member Rkrutledge's Avatar
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    Quote Originally Posted by mchapa View Post
    It works great....adjusted once a year....the original stuff last a long time....
    So if I am going to go back to using the spark generator from the Dyna 2000 what else needs to replaced?

  12. #12
    CB750 Enthusiast mchapa's Avatar
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    Click image for larger version. 

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    Remove the dyna trigger switches and block.....and install the original points...it has 2 wires ..one each to coil....

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