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Looking for a steady idle with no miss

badbrad Jan 6, 2019

  1. badbrad

    badbrad Senior Member

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    Been too long- still can’t ride after carb rebuild and many years. I’m usually pretty good at keeping my bikes going but I’m stumped right now. I let my low mileage 900 set for years because I got aggravated last time my carbs were rebuilt as it would not stay running. Rick rebuild my carbs about 3 years ago from sitting and when I put them on, they ran like new which I expected getting them done by Rick. The issue was as soon as the bike got hot, around 210 degrees, it would start to miss and then cut off. I changed coils, replaced plugs and wires, did a lot but did not help. If I Let the bike cool down it would start back up nicely and run good until it got to 210 degrees and would start missing again. I finally quit troubleshooting and let the bike sit for several years. I’ve fineally jumped into again and I’m not going to ruin this carb rebuild that Rick just completed and going to find out what’s causing it.

    I put the carbs on the other day and cranked it up and it’s still doing what it did years ago and that’s start running rough, missing and eventually cut off when it gets up to temp. If I remember correctly this bike should idle sweet around 1000 RPM which it does until it starts to miss when it gets hot.

    Like I stated, plugs wires and coils have all been verified so I’ve ordered a set of pick up coils and known good ECM. Do one of these sound like it could be an issue? The tank is clean, pingel filter and petcock is new and working as it should. The valves sound happy to me and don’t feel they are an issue right now but they have not been verified yet. I just don’t think that’s causing this issue.

    I would love to hear everyone’s input on helping me troubleshoot and getting this 6,000 mile bike running good again. I could rig up some wires from the primary side of the coils so I could watch the pulse coils and see if I can see them miss with a test light when it gets up to temp.

    I have not balanced the carbs yet but they are pretty close. The bike will idle smooth at low RPMs up until the bike gets around 210 degrees.

    Thoughts? There is only 6000 miles on the pulse coils but they are sure are old. Usually when my bikes acted like this, it was the spark plug cables that needed a 1/4 inch cut off, no go this time! All that’s been done.

    I’m running the new NGK PLUG boots and each are reading around the 5k ohms as needed. New wire was used as well.

    Thanks team in advance for any input!

    Brad
     
  2. 87kawzl

    87kawzl Senior Member

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    Did you use 7mm solid core wire. Sounds like they may not be seated. I know you say they were done but you know....
    Maybe change the plugs, sometime they can be defective.

    Carb cleaner sprayed around the intake boots can be tell tale for vacuum leaks too.
     
  3. markus56

    markus56 ZL-OA Co-owner Staff Member Administrator Super Moderator Supporting Member

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    Sounds like pulse coils to me Brad.
     
  4. badbrad

    badbrad Senior Member

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    Hopefully the pulse coils or ECM will take care of it. Should have these in a couple days.

    Thanks Markus, will post results soon!


    Brad
     
  5. markus56

    markus56 ZL-OA Co-owner Staff Member Administrator Super Moderator Supporting Member

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    Be sure to get the gap right on the pulse coils.
     
  6. R. J.

    R. J. Senior Member

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    :hello: Are you using OEM coils. A lot of the cheap ones are junk. After the bike gets up to running temp they break down. Check all of your connections going to the ECU/CDI, fuse box & pic up coils. If they are rusted or corroded you will have high resistance. Clean them up with contact cleaner or what I use is distilled white vinegar 8 oz. mixed with a table spoon or 2 of baking soda. Put it on both sides of the connection of each plug with a small brass wire brush & brush it real good. Next clean the plugs with brake parts cleaner then blow it dry. Last but not least put a dab of diolectric grease on each pin of each connector before plugging them back together. One other thing check for stiffness in the wires if needed. If they do not bend easy you may have corrosion under the wires insulation. Corrosion = high resistance. Check the stiff wire with a omh meter. If you are reading less than an ohm of resistance it is good. If you do find high resistance cut that section out. If needed add a new section of wire by soldering it in. Use heat shrink & not tape. Before doing any of this DISCONNECT your battery. Also a cracked pic up coil will cause what you have said in post #1. I done all of my connectors in my wiring harnesses in all of my bike as stated. By doing this you will never have a corrosion issue again.
     
  7. badbrad

    badbrad Senior Member

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    Yes, pulled that info and ready! What a strange event this has been and Not stopping until it runs right.
    Thanks R.J. I have completed. Inspections of most all that at and everything looks almost brand new with the small wiring. I did contact clean all the connections, cleaned grounds and put the dielectric grease on everything I cleaned and inspected. All the secondary wiring on the coils is good and new and has been verified. My money is on the pulse coils because it slowly starts to creep in and act up. It will idle at 800 rpms slick as butter when cold but when we starting getting to 200 degrees and beyond, she starts to miss and finally skip enough to cut it off when idling at 1500rpms.

    Pulse coils should be here soon. If the ECM was bad, I believe it would be acting much worse but we will see as both ECM and pickup coils are on the way. Will do one at a time and report back.

    Thanks, found a link to purchase pulse coils in a previous post of yours. Partzilla had the best price.

    Do they make a new ECM for our bikes or are we stuck finding use ones? What’s the alternative when dried up?

    Brad
     
    R. J. likes this.
  8. 87kawzl

    87kawzl Senior Member

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    Seeing the symptoms start when it's warm I think Marcus is on the money with his diagnosis.
     
  9. R. J.

    R. J. Senior Member

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    :hello: I bought a new set of OEM pic up coils from partzilla a few months back. I also have a used set from a newer low mile connie which I've had for a few years. I agree with the others :notworthy: change the pic up coils first. I thing Dayna makes a ECU/CDI for our bikes but they run around $350.
     
  10. badbrad

    badbrad Senior Member

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    And yes R.J. they are original style coils but they have been verified as good with no issue. I even took another known good coil and swapped each of them, same thing.

    Just wanted to make sure I answered your question and we can check it off the list. It’s going to be fun getting the pulse cover not to leak, never seems to be leak free the 1st time around.

    Brad
     
    R. J. likes this.
  11. R. J.

    R. J. Senior Member

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    :hello: Clean all the old gasket off then sand it by laying a 8x8 sheet of 100 grit sand paper on a flat table. Palm the pic up coil cover with your hand & go in a figure eight motion checking it for trueness. Repeat if necessary. Are you using a new gasket.
     
    badbrad likes this.
  12. badbrad

    badbrad Senior Member

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    Yes, I have ordered a new factory gasket! I also have the torque specs for install. I think a couple bolts get threadlocker as well. How about gasket sealant? You use it?

    Brad
     
  13. R. J.

    R. J. Senior Member

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    :hello: I use just enough to hold the gasket in place. Pematex gray gasket maker. Just a dab in 4 corners or you can use 2 or 3 case bolts as an alignment aid.
     
  14. 87kawzl

    87kawzl Senior Member

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    I definitely wouldn't use it on both sides of the gasket. I don't think I've used any.
     
  15. badbrad

    badbrad Senior Member

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    Got it, thank you!


    Brad
     
  16. R. J.

    R. J. Senior Member

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    :hello: Yes really no need for it when using a new gasket.
     
  17. badbrad

    badbrad Senior Member

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    So.... both the pickup coils and ECM cane in today. Since it only took a minute, I changed the ECM to find the same results. Bike starts great, isles good and low then starts to miss at temp. THE ONLY thing I know to do now is change the pickup coils. I am also going to balance the carbs but don’t think that’s got anything to do with it. Carbs are fresh and runs great when cold.


    I will get the pickup coils changed as soon as my gasket gets here and see what happens. Lord I hope that’s it, it’s been too long since she’s been down the road.



    Brad
     
  18. R. J.

    R. J. Senior Member

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    :hello: We all agree that it's the pic up coils :notworthy: so we all can't be wrong or can we :laughing7:.
     
  19. badbrad

    badbrad Senior Member

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    We shall soon see! 30 lashes with a wet noodle if wrong.
     
  20. 87kawzl

    87kawzl Senior Member

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    It's something electrical that is affected by heat. Watch wagging your wet noodle around it!
     
    badbrad likes this.

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