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Diagnosing Cyl 1 (no spark)Misfire

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  • Diagnosing Cyl 1 (no spark)Misfire

    I'm looking for procedure to fix the no spark condition on Cyl 1. I tested for spark on Wire 1 and it's perfect, tested on Wire 2 and the spark is almost non existent and it's super weak. I was pulling some other stuff off a parts bike and I grabbed another coil, already swapped it and zero difference so the issue is not in the coil itself, or the plugs, or the plug wires, any help would be greatly appreciated... The bike is a 2000 roadstar 1600cc
    Last edited by OlyWaMd; 01-22-2022, 05:06 PM. Reason: Mis worded some stuff....

  • #2
    Make sure that the low voltage wires on the coil are connecting tight…. Its a spade connection which can sometimes become loose over time… check both ground and hot wires….
    also confirm that the throttle cable housing is not grounding the coul where the low voltage wires attach….
    both plugs in the cylinder should fire at the same time…. Are you sure its a good spark plug?

    Comment


    • #3
      Tcontrol.. already changed both plugs on Cyl one and raised the coil of the bracket with some washers so I'm pretty sure nothing's grounding out, maybe that's the throttle cable thing u saying idk but doesn't appear to b grounding, has to be electrical maybe a sensor or break in the wire between coil and computer, the diagram shows something called relay unit.,. Idk what that is or where thats at but it got something that looks like a cdi on the front of the bike with 3 white wires a red and a black but the coil just has smaller red black with orange. Idk I'm kinda new to bikes but I've got like 4 or 5 running in the last year....

      Comment


      • #4
        According to schematic…. One coil pak drives both spark plugs…. If one plug is not firing, the problem is the coil pack, spark plug wire, or the spark plug… (there is a resistor in the plug wire… you may want to check it)
        You have already stated that the coil pack has been changed and now a new spark plug…. Since you have also stated that one of the plugs is firing correctly and the other one is not…. According to schematic…. That is very unlikely… please reference the attached picture… is it possible that you have a second defective coil pak… also unlikely… try moving the coil pak to the #2 cylinder and see if problem follows… also move spark plugs and see if problem follows… (i assume that you have spark plugs pulled so the motor can be spun without compression)

        maybe this pic will help in isolating the problem… the working spark in cylinder #1 should be same color and intensity of spark for either #2 spark plugs… is this also true?…

        Comment


        • #5
          Tcontrol any help really means a lot to us the bikes for my wife who has had her foot amputated from diabete, were trying to get her back on the road but it's been a long process.... There was comications with the amputation and she's just now after thre years getting a prosthetic, I have been practicing rides across town with only my left leg and I have been able to do it but she hasn't been confident enough to try it without the prosthetic which were getting in a few weeks, anyway I think your on the right track I am going to switch the coils and see what happens and I will post it... She really likes this bike because she doesn't have any trouble sitting on it like she has with my other bikes, we also have a Honda cb900c that she hasn't even tried to sit on yet, I still have to figure out what's going on with the brakes on that one and it's across town at my father's but it's a cool bike too, anyway just thought I would say TY AND HAPPY RIDING!!!

          Comment


          • #6
            I would be happy to help you diagnose and repair this problem…. A volt meter would also be beneficial to isolate this problem if you have one….. (reading ohms can isolate this pretty quickly)
            let me know the result of your coil swap…

            Comment


            • #7
              This may sound silly, but make sure both spark plugs for cylinder 1 are connected to the same coil. The spark gaps on both plugs should be the same, and both sparks should be the same intensity, since the same amount of current should be flowing through both plugs in this series circuit.

              Comment


              • #8
                So I tightened the connecter on the red wire that goes in back of the coil, now I have spark on that wire the same one that was missing but when I tested the spark with a grounded spark plug I saw one spark that was a nice bright blue color and the rest of the Sparks were kinda dull but they were all on time it seemed, still getting some backfiring/missing and I can't start it without starting fluid even though the choke is working, I'm thinking it's a weakened coil, the second coil, the one that's on it now was a junkyard coil so I'm thinking try a brand new coil and I should be good. What do you guys think?? P.s. I will post the video of her first ride after the surgery.....

                Comment


                • #9
                  only way to test a coil properly is with a VOM, cant go by visual, as hi pressure in cylinder. and hes correct, the metal jacket on throttle cable will wear thru 12 v lead on right side coil 12 v input, causing intermittent grounding.also, if you run a RS with a plug wire off , it can fry a coil, dont ask me how I know

                  Comment


                  • OlyWaMd
                    OlyWaMd commented
                    Editing a comment
                    So when you check resistance your pulling power off that coil into your meter, it's not much but you can see the numbers drop in a rythmic fashion if you hold the leads on them long enough. The coils I have start dropping very quickly, so the thing is when they get down to zero the coil won't recognize that a circuit can be there so they don't work, you can still fix them if this happens but you need to reverse polarity on them or charge them touching the earth, don't ask me why this works it just does, the same thing goes for 12v batteries, I have heard the tearm fried used and it frequently means something that's been zero'd voltswise. Idk what a vom is? But are you referring to when a cylinder will ignite on compression regardless of spark? This coil is left coil if your sitting on the bike it's the left one. First part of this response is not something I know as fact it's just an observation I have recently seen in a couple different instances and I believe this is the case, know for sure... Definitely not.... Lmk what you think....

                  • davej
                    davej commented
                    Editing a comment
                    A VOM is a Volt Ohm Meter

                • #10
                  weak coils are very uncommon. The only coil issue is when there is either external leakage of spark going to the frame of shorting out against the throttle cables. Wrapping the coil with a electrical tape would correct the issue. If it does then you choose if you want to buy a new coil. simply installing the original coil would also be a good diagnostic tool because when 1 coil being bad is rare having 2 bad coils is even more unlikely. Sometimes simply removing the cap and clipping the wire back about 1/4 inch to get rid of any corrosion at the end will help. You can also remove the resistor from the cap and replace it with a pc of heavy wire the same diameter that will fit in the resistors place. that will tell if the resistor is bad. If it is bad you can leave the wire in there and be fine. Years ago that was a mod that many members did. They just got rid of the resistors and replaced them with that heavy wire/cable. I don't remember what gauge they used though. Also make sure you have the correct wire going to the correct plug, it makes a difference.

                  Comment


                  • #11
                    Davej is absolutely correct in his assesment….

                    Each coil drives 2 spark plugs in parallel… if one plug fires and the other one does not, the issue is with the spark plug wire… either the resistor connection in the cap, a weak connection to the plug wire from the spark plug, or the end of the wire needs ‘refreshing’…

                    if the coil low voltage wire is arcing to the throttle cable…. Tape the throttle cable and re-orient if possible…. The symptom would be a weak or no spark on BOTH spark plugs associated with the coil… It is possible to damage an ECM if you continue to short circuit the pulsing transistor (internal to the ECM)…. Try to correct this problem ASAP before any damage occurs….. or do a little preventive maintenace and address this before it occurs…

                    the coil is a simple electrical transformer that steps up the low voltage to high voltage… i have never heard of one acting as a capacitor which needs to be reverse charged/ or arced to regain function…. (What the OP referred to)….

                    a coil can become damaged by excessive current (missing load such as a bad spark plug, bad plug wire connection, excessive heat/age damage to the electrical insulation on plug wire/ case, or short circuits on the coil winding)…. An involved explanation of a pulsing magnetic field collapsing causing current spikes is beyond the scope of this discussion….

                    OlyWaMd would most likely solve his problem by taping the throttle cable to electrically isolate from the coil, refresh the spark plug wire ends as per DaveJ’s response, checking the resistors that are located in the spark plug cable caps, and tightening the low voltage connections on the back of the coil…

                    sometimes it might be advisable to crimp new spade connectors on the low voltage wire connections to the coil to establish good electrical continuity…

                    Have you performed all these tasks OlyMaMd?…

                    this may solve your starting issue regarding starting fluid instead of using the choke (enricher)…. Enquiring minds and all that……..


                    Comment


                    • #12
                      Tcontrol been away for a bit just got back to the homestead... I believe the computer is probably no good I was putting another end on the low voltage wire and I did not disconnect the battery, anyway the wire stripper hit the frame and now I have zero spark no matter what I do.... I got new coils coming in the mail on Monday I believe, I'm not sure if they come with the wires or not, I would have to go back and look, yeah everything you guys have said makes sense has to be within the wire... That's pretty interesting about the capacitors davej posted, I'm not sure what the deal is with all my extra 12v's.... If they have been stored on the ground they loose all voltage and become un chargeable but it seems that if I arc them I can revive them.... Idk much about electronics just a backyard tinkerer....

                      Comment


                      • #13
                        I haven't been able to figure out how to take the wires off the coils without butchering them, there's a plastic bracket thing but it just gets busted the second I touch it.... I think it's a better job for the other half just need to know how to properly transfer the wires off the coils....

                        Comment


                        • #14
                          I have a couple spare1600 cdi's if you need one for testing....all came off my own bikes and operated fine....just pay postage....
                          LET'S RIDE

                          Comment


                          • #15
                            Silly question…… why did you have the key on when you were changing the electrical connection on the low voltage coil side?? You most likely burned the 15 amp ignition fuse and did not damage the ECM..

                            you wrote that you were trying to remove the high voltage wires from the coils… do not remove the wires… take the end caps that attach to the spark plugs off and refresh as per davej’s suggestion…

                            if english is not your native language, than i can understand that there may be some miscommunications on these repair suggestions…. Please request help from someone who is more proficient in following these suggestions…. You may be doing a lot of damage to your bike if you continue to work on it yourself without the proper mechanical aptitude or common sense proficiency….

                            This is not a derogatory comment to you in any way, shape, or form…. We would like to help you get your bike running properly at a minimum cost to you…. Unfortunatly, your responses to our suggestions seem to point to a certain confusion regarding your understanding…. This may lead you to causing unintended damage to your bike and costing more money to repair… i am certain that we do not want to advise you in a way that would cause damage to your bike…

                            i am concerned about this…. It may be to your advantage to seek help from a clinic member that lives in your area or maybe consider taking it to a competent mechanic…

                            Comment


                            • Brad_G
                              Brad_G commented
                              Editing a comment
                              An old Clint Eastwood movie quote comes to mind...."A man has to know his limitations"

                            • OlyWaMd
                              OlyWaMd commented
                              Editing a comment
                              Sounds more like megadeth it's on countdown to extinction "hello me"

                          • #16
                            VOM is a volt ohm meter , multi-tester

                            Comment


                            • #17
                              Tcontrol it usually takes me a second to understand stuff so I don't always get it right in my responses, but I understand about the wires just not how they came apart and was taking them off the coil and for some reason I got that confused with "take apart the wires" I can see how this makes it seem like I'm not familiar with reading or something, but yeah very familiar, good not at all.... So when you take apart the wires there's a resistor in there and that can be replaced with a similar diameter wire probably like a grounding wire non braided type wire, anyway the numbers I get testing the original coil I will post here in a minute, I tested with VOM voltage/ohm meter and both sides had resistance. Another side note is that whatever happens to the bike was well on its way to happening anyway.... At any given point I usually have around 4 or 5 works in progress, just picked up a new on yesterday a 96 virago, anyhow don't worry about mis direction causing damage, what I was referencing earlier about putting another end on the low voltage side was after I had put a different junkyard coil on, tried starting it and same thing, I had just been cranking the bike, I notice the end on the low v wire was loose when I changed the coil so I have much better ends for those anyway there fully encased in hard plastic not the soft little boot things so yeah that's the story on that....

                              Comment


                              • #18
                                High v end 35.2, low voltage side 2.5 kinda bounces between 2.2 and 2.5 this is the original coil that came with the bike, un damaged

                                Comment


                                • #19
                                  Well this was the resistor from each wire, I took these apart over a table very carefully, right side has like the middle of the resistor and one of the ends, left side normal... Lol.... I believe this was most likely the problem, I expect that I'm going to need another computer too which I can get from the bike junkyard next door. So a little back story since I've had the bike I've tried to crank the bike several times, had it started and running probably 3 times, last time the pipe on the misfiring side got red hot and now I won't try and run it with any signs of misfiring, anyway the point is I'm concerned about maybe I had already damaged the computer and most of this was all before I found this web site so nobody need be concerned about advice causing damage.... Lol ... Anyway I'm replacing the resistor with the one from the coil/wire I butchered, putting it into the original coil, thinking it probably won't matter if I try and fire it to see if this was the whole problem.... The other option is to run go grab the other computer and put that in before I try it but if the original computer is already damaged then I would essentially be beating a dead horse lol... It won't feel pain... Lol....
                                  Attached Files

                                  Comment


                                  • #20
                                    Since I've already tried I believe two other coils and the exact same result has occured logically I believe the bike had come with a damaged computer. When I first got the bike: First attempt to fire this one I noticed the carb pissing fuel, I cleaned the carb and changed out the gaskets and such from a carb kit, second attempt had to use alot of starting fluid and eventually got it to run only while babying the gas so I shut it down, obvious misfire, other 2 attempts where after attempted repairs but the point is after cleaning the carb the bikes acted exactly the same every attempt, previous owner probably tried several times and cooked the computer....

                                    Comment

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