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Spark issues -- no life on the front cylinder.

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    Spark issues -- no life on the front cylinder.

    I'm on a fairly fresh (maybe a 2-3k on it) 700 build. while I was riding the other day, I lost my front cylinder. Determined it's got no spark.
    I think my CDI box may have died.. Just looking for some reassurance before I either yank the clutch cover to visually check the pulse coils and trigger wheel (I found an old thread where a guy mentioned his trigger wheel being loose and not spinning?! I don't really think it's this, but the thought scares me...) or drop money on a CDI box.. which I can't do for another week or two.

    Coils tested fine as far as ohms, primary and secondary.
    Pulse generators as well. Both had nearly identical ohm readings.
    I have spark on the rear cylinder.
    Checked resistance/continuity on all the wires..
    Checked for 12v to the cdi, 12v to the coil.
    Checked grounds.
    Kill switch is good. N switch is good. Clutch switch is good.
    Swapped a known good coil in up front. Still no spark. (works on the rear)
    In order to eliminate my bad eyes I even tried a timing light--good on rear, nothing on the front.

    This weekend i'm going to try swapping the wires around to the cdi from the pulse coils--I figure that way I can eliminate the pulse generators as the culprit and be sure it's the CDI. I think if I hook the rear pulse coil up to the cdi input for the front coil and vice versa... then have spark up front but not in the back, front pulse coil would be bad. I am incredibly tired and a bit frustrated though so i'm not sure if all that even makes sense..

    Anyone?

    #2
    It sounds as though you've went down a pretty good diagnostic road. If you are sure of all your readings, that pretty much just leaves the CDI box or maybe the pickup coil has come asunder. I have seen, a few times, where the clutch basket sheds a piece and it whacks the pickup coil, bending it away from the ignition rotor. Yes, you can try swapping wires around but don't try to run it like that, you'll have some impressive flames out the intake and exhaust from the wrong spark timing, which I'm sure you know.
    J.D. Hord
    Keeper of Engine Nomenclature, 9th Order

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      #3
      i usta believe a failing cdi would quit completely, but i discovered on one of my '86 VFRs that a bad box can fire ok on most cylinders but not spark on just one.

      gallery_3647_3505_141983.jpg

      "It's only getting worse."


      MY rides: '97 VFR750, '90 Red Hawk, '88 Blue/Black Hawk, '86 RWB VFR700 (3), '86 Yamaha Radian, '90 VTR250, '89 VTR250 (2), '73 CB125, '66 Yamaha YL-1

      Sold: '86 FJ1200, '92 ZX-7, '90 Radian, '73 CB750, '89 all-white Hawk, '88 blue Hawk, '86 FZ600, '86 Yam Fazer 700 , '89 VTR250, '87 VFR700F2, '86 VFR700F.

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        #4
        Originally Posted by Hordpower View Post
        . Yes, you can try swapping wires around but don't try to run it like that, you'll have some impressive flames out the intake and exhaust from the wrong spark timing, which I'm sure you know.
        Yes, but be careful,

        Found it!
        Don't spend money and buy, spend time and learn.

        Comment


          #5
          Originally Posted by Hordpower View Post
          It sounds as though you've went down a pretty good diagnostic road. If you are sure of all your readings, that pretty much just leaves the CDI box or maybe the pickup coil has come asunder. I have seen, a few times, where the clutch basket sheds a piece and it whacks the pickup coil, bending it away from the ignition rotor. Yes, you can try swapping wires around but don't try to run it like that, you'll have some impressive flames out the intake and exhaust from the wrong spark timing, which I'm sure you know.
          thanks a ton JD. next weekend I plan on pulling the cover and having a look inside before i buy a new cdi. any chance you have any more of those ignitech boxes lying around?

          Also, thanks for the safety tip, lol. I intended on doing it with out the wires hooked up to plugs, I'll hook my timing light up instead. Good note for anyone stumbling on this in the future who wants to try it for diagnosis.
          Last edited by rpm10k; 3 Weeks Ago.

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            #6
            Disappointingly... I managed to dig my spare CDI from the hawk I wadded up years back.. plugged it in...but still no life up front.

            I also swapped the wires round on the 4p plug--yellow swapped with blue, yellow/white swapped with blue/white. I had no spark on either cylinder. I swapped the wires back around, and had spark in the rear again.. but still not up front.

            My thought process was this...
            I KNOW 1. the rear pulse generator is working. and 2. the cdi is doing what it's supposed to for the rear, because the rear cylinder sparks.

            That said... I figured, front pulse gen plugged in place of the rear, I know that the cdi functions at least for the rear bank.. so I expected, if the front pulse gen was bad, i'd get no spark on the rear bank. I expected that if the CDI was good, the rear pulse generator that I KNOW works hooked in place of the front, i'd have spark in the front. No spark on either bank... bad CDI and pulse generator at the same exact time?? The thing will fire right up on the rear cylinder.

            I have a friend with the same exact issue that started about the same time as me.. he's checked all the things i have bar swapping wires around in plugs.. no spark up front. We're both stumped.

            Guess i'll be ordering a gasket and pulling my exhaust and clutch cover off.



            EDIT: Just swapped out the wiring harness for giggles.
            No change. and maybe both of my CDI boxes are magically bad. I have no idea where to go next aside from pulling the cover and swapping out the pulse generators.. at least i've got some spares from the motor I blew up.. and finding a known good cdi box


            I am frustrated.
            Last edited by rpm10k; 3 Weeks Ago.

            Comment


              #7
              Bizarre. I can't really figure out how you didn't get spark on the front cylinder with the pickup wires reversed. Unless there is a wire continuity issue somewhere? Are you checking for spark with a spark plug? It's a good plug? What's your voltage? If it drops below ~11.0v one cylinder will go dead... but it's usually intermittent. How's your wire harness ground at the rear brake reservoir? That causes issues that seem to defy logic, sometimes.
              J.D. Hord
              Keeper of Engine Nomenclature, 9th Order

              Comment


                #8
                Originally Posted by Hordpower View Post
                Bizarre. I can't really figure out how you didn't get spark on the front cylinder with the pickup wires reversed. Unless there is a wire continuity issue somewhere? Are you checking for spark with a spark plug? It's a good plug? What's your voltage? If it drops below ~11.0v one cylinder will go dead... but it's usually intermittent. How's your wire harness ground at the rear brake reservoir? That causes issues that seem to defy logic, sometimes.
                I can't make sense of it either. I swapped wire harnesses entirely to eliminate that as an issue. When I did this I also hit the spot where that ground wire bolts onto the frame by the reservoir with a wire brush.

                I am checking for spark with a plug in the boot, and also my timing light because my eyes are kinda bad. Timing light lights up and the plug sparks on the rear.
                Also, I checked each plug wire on each coil. Both work on the rear, neither work on the front.

                I even checked continuity from the plug I had in the boot, to ground to make sure i was making a good contact to ground. Spark is nice and bright on the rear and ground is good.

                Voltage is ~12.5 last I checked. I also hooked a jump box up to eliminate that as an issue. also, it's a 3 week old Yuasa in the OEM size. another edit: brand new NGK DPR8EA9 plug from the box.


                I guess at least I'm glad no one has said I missed something obvious. I'm in IT now but I worked in shops for the last decade or so.. Usually I'm pretty good at diagnosing electrical issues.
                Last edited by rpm10k; 3 Weeks Ago.

                Comment


                  #9
                  I’m the friend Hawk Rider mentioned. Should I have battery voltage on all the pins in the 6pm connector? Key on, run switch on, one terminal on Batt negative and other tested each pin in the 6p connector. Two had 10.5, one had 0.0, one had 3.48.

                  thanks

                  Comment


                    #10
                    Just for sanity's sake:

                    CDI 4p
                    FR pulse 463ohm
                    RR pulse 461 ohm
                    Checked all 4 pins continuity to ground, no continuity like expected.

                    CDI 6p:
                    Yellow/blue to green, battery voltage
                    Blue/yellow to green, battery voltage
                    Black/white to green, battery voltage
                    voltage goes to 0 when kill switch is flipped.
                    Green to battery (-) continuity, 0.001 ohms.
                    Green to reservoir ground strap continuity, 0.001 ohms.

                    Front Coil:
                    Primary coil resistance: 2.5ohms between blade connectors.
                    Secondary coil resistance: 31.58 kohms between plug caps
                    battery voltage at coil rh blade connector.

                    I sent you a few texts. but I think we've got different issues with the same symptom from what you just said. You need to do some checking on your wire harness. if you wanna borrow my spare.. you are more than welcome to. only takes me like 30-40 minutes to swap them, personally. but trace that battery voltage through the harness/connectors and see where it drops like that.
                    Last edited by rpm10k; 3 Weeks Ago.

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