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Constantly poping at idle on left cylinder

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by thecptn, May 29, 2008.

  1. I have a 81 XS650, which has had a peculiar problem ever since I got, it has always had problems on it's left cylinder, problems ranged from completely not running on that cylinder for a while to just after firing on deceleration, I have had the bike taken to a tuner, who him self is stumped on what it could be, I have had the carbs tuned, cleaned, and re jetted, hell I even fitted new diaphragms and new rubber intake boots, yet the problem still remains, it has gotten worse when we tryed to locate the air leak, we sprayed carb cleaner on the left carb intake boot and found out it was sucking it in, when is shouldn't off, how ever we could not redo this as we ran out of carb cleaner haha.

    How ever, it has new gaskets and all on the intakes, and every thing as far as I can tell is drum tight, I dont know how it could be sucking in air.

    Any remedies?

  2. Check your valve clearances, and then try !
    Could also be a valve sticking in it's guide!

    Hope it helps
  3. Valves have been checked and ignition timing all checked, all within clearances.
  4. exhaust leak or ignition problem.

    Does it run 2 coils? try swapping the coils over.

    Swap plug caps and leads all separately.
  5. Unfortunatly, it only has one coil, how ever, I found out this moring the left carby flooded, had a nice little wet patch on the garage floor, this has happened twice so far, I think I have found my smoking gun..
  6. a carb valve needle may have dropped

    mine used to stink of petrol and pop at idle before fixing this prob

    or maybe you have a crack somewhere letting air in, check diaphram gasket too
  7. Re: Constantly popping at idle on left cylinder

    He is not much of a tuner, seriously. Or he didn't try very hard.

    The other thing that can give similar effects is bad idle sync.

    I can't remember the last carb I saw which didn't have a drain screw on the float bowl. Fit clear plastic drain hoses and lift them up beside the carbs with the ends of the hoses in the air well above the venturi - this will show you the dynamic or real float level.


    Trevor G