Missing at constant speed?

Discussion in 'Engine, Fuel and Exhaust' started by Bodeen, Jun 18, 2014.

  1. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

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    2003 Road King, new 21 mouse cams, new S.E. plate and pump, S.E adj. push rods, Street port heads, new valves, springs etc. Rinehart TD'S, CV carb with sporty needle, 46 slow 190 main.

    In second gear at a steady speed like around 25-30 mph. The exhaust note sounds like the motor is missing. Idles great and runs strong when twisted back. Just an odd sound that I cant figure out. New plugs, different needles in carb and shims etc. Still there. Not even sure it missing really but sure sounds like it to me. Have not changed plug wires yet..... Any ideas?
     
  2. traveller

    traveller Member

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    just a thought but it could be your cams. I know I have a s&s 570 cams in mine and it rats a little at low speeds and rpm. I don't know what your lift and duration and valve over lap is. cams with a longer duration than stock will sound different. but from what you described sounds like your bike is ok, I could be wrong but it's a thought..\
     
  3. STEVE07

    STEVE07 Well-Known Member Staff Member Super Moderators

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    Check for an exhaust leak. At a steady rpm a small leak can sound like a miss.
     
  4. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

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    Wondered about that myself. I haven't heard others mention this with this cam though. FWIW, it did it with the stock heads too.

    Good point and I'll check it, but the exhaust fit back up real nice from front to back.
     
  5. STEVE07

    STEVE07 Well-Known Member Staff Member Super Moderators

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    Get someone to put on leather gloves. I use welding gloves. Start it up and have them hold their hands tight over the tail end of the mufflers then check all of the joints for a leak.
     
  6. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

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    Yep, I'll check that tomorrow.
     
  7. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

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    Exhaust seems tight. Wondering about the lifters now. If I had a lifter that was not right it seems it would exhibit the symptoms I am having. Brand new Comp Cam lifters. May go back to HD 30K mile lifters this weekend to see if that solves it.
     
  8. BUBBIE

    BUBBIE Well-Known Member

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    I doubt it to be the lifters... IF me with the new Comp lifters , Take them down to .140 and see...

    IS the motor running: More like a flat spot? Like it is there but Not?

    Probably that cheap carb you got from me. LOL.....

    I'd double check the float level.... keep on the high side... OR maybe add a tad to the slow speed jet.......
    IF you add to .048 to the slow speed jet, it might go away? You can try or have you..?

    Is the feeling like a surge or kinda not smooth there? I still think the idle/slow speed jet Increase OR decrease might tell you something. The big jet usually won't be used at a slow light steady speed...

    Let me know if you try any of this and IF it helps.:small3d023:

    I also Doubt it to be cam related... It might be JUST exhaust revision... You can buy for 25$ exhaust cone inserts for the head pipes...

    signed....BUBBIE
     
  9. stray dog

    stray dog Junior Member

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    Bodeen,
    I've got about 1200mi on the 21's now and have experienced this also. Exactly like what you've described or combo miss/flat spot sound/feel. Maybe at the right rpm & load this is just what these cams do and traveler hit the nail on the head here in post #2..??
    I don't have any problem rolling on the throttle from that point nor is there any flat spot rolling on from any point.

    BTW I'm EFI.....

    Also,this also doesn't happen all the time, just once in awhile. Maybe when the bike isn't fully warmed up (not exactly sure).
     
    Last edited by a moderator: Jun 20, 2014
  10. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

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    Just replaced front cylinder lifters with the old ones. No change and no bad sign on the new ones. I am down 3 turns with my S.E. tapered P/R that are 24tpi.
    I would think if it were float level it would do it when holding it wide open for awhile. It runs great when rolled on. Its just at that higher RPM in the gear. If you hold the RPM steady it sounds like a miss. Doesn't feel like it, sounds like it. Also when you slow from a faster speed to a constant RPM it will bah, ba,bah,ba, bah. Its not a dead spot by any means, you can roll on and rolls. I wouldn't even call it flat. It just sounds like its missing.

    The slow jet seems right cause I can make it stumble rich and lean.I'll jet up next and see. I'll let you know....

    Thanks,