Rear Cylinder not running unless Carb Intake 90% covered

Discussion in 'Sportster Models' started by ejohn90472, Apr 22, 2008.

  1. ejohn90472

    ejohn90472 New Member

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    I have a 2002 Sportster 883 with 728 miles on it. The bike starts with the enrichment cable pulled all the way out. However. once the bike starts it will only run above 2500 to 3000 RPM with the back cylinder kicking in occasionally. As I try to drop the idle the bike wantz to die with the rear cylinder not running correctly and staying cold.

    I checked the spark on both the front and rear cylinders – the front plug fires straight across the spark plug while the rear cylinder appears to be sparking in all directions. I changed the plugs and that still didn’t change the rear cylinders performance nor correct the problem.

    What did work is when I removed the air cleaner assembly and placed my hand over approximately 90% of the carburetor intake. The bike then appeared to run fine. I was able to push in the enrichment cable while maintaining my hand 90% over the Carb intake. I’m not sure what this could mean and was hoping that the Harley Guru’s here could HELP!

    Any recommendations would be appreciated. Thanks


    ejohn90472
    2002 Sportster
     
  2. glider

    glider Veteran Member

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    If the bike has been sitting a while stored, sounds like the low speed jet is clogged or you have an intake leak, possibly on the rear cylinder. Drop the float bowl if you can handle this and clean the carb/jet out.
     
  3. bikermonkey

    bikermonkey Active Member

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    I don't know how reccomended it is,,,,,but I have found intake leaks by spraying ether around the intake boot area,, the idle will increase if a leak is present. I'd more likely suspect a clogged jet. :coffee
     
  4. 67hat34c

    67hat34c Active Member

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    Eather is way too dangerous for this. Use wd40 or simply put your fingers around the area, you can feel the air movement.
     
  5. glider

    glider Veteran Member

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    What's dangerous about a squirt of WD40 around the boots to check for a leak. Most times a small intake leak cannot be felt with the hands, it's not like a leak where air is pushed out.
     
  6. Zamadan

    Zamadan Active Member

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    Think he meant to say ether is to dangerous, use WD40 instead.
     
  7. glider

    glider Veteran Member

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    OOPS, You're right there .I missed the "ether" part. For sure you would get a bang out of that.

    Have to learn to read slower:D but I swear that post read differently when I replied to it.
     
  8. cansel kansu

    cansel kansu Member

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    Spraying water will do the same. if there is a leak, water will be sucked in and idle will also increase. this is very common way of finding intake leaks at most of the engine repair workshops.
    I had pretty much the same problem till yesterday.
    I first changed the places and then replaced the spark plugs with new ones, no help!
    First changed the places of spark plug wires connection points on the induction coil end and then replaced with new ones, no help!
    I got my compression ratio measured, 9 bars both cylinders, no prob...
    Tried to tune the ignition angle by rotating the igniton module, no help. (I was the first one unscrewing the fixing screws of the ignition module plate, there was no screw tightening mark on any other place before I started to tune) then did the static tuning before closing the cower.
    I was just hopeless about finding a solution and started to check ebay for buying a single fire igniton kit or a complete upgraded carburator yesterday then I wanted to give a try for tuning the carburator. I took the carb out and set the idle mixture adjustment screw only 1 turn off from the max in position. now I can hear that both cylinders are firing. the new problem is, idle rpm increases as the engine warms up, up to 15-20 minutes. when I adjust the idle after 20 mins, then cold running will be too low. this is not annoying me as much as loosing the back cylinder so I consider my back cylinder problem solved.
    any suggestions for the idle fluctuation issue is wellcomed.
     
  9. glider

    glider Veteran Member

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    You may try adjusting the idle mixture fully warmed up to the highest and steadiest setting. Too many people think the 1 turn open is the place to be when it's not at all. It's an "adjustment" that will return a good running motor when it is done properly as long as other areas are not causing a problem.
     
  10. cansel kansu

    cansel kansu Member

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    actually, I was fed up burning and sweating under the sunshine while working on the bike and didnt want to take the carb out and install back for each little tune on the screw. the first try was 1 turn off and I heard the back cylinder firing. so I just wrapped all and ran to the shadow... :) I am pretty sure that this is not the best setting but no coughs, no hassling off the idle, both cylinders firing... how happier could I be? so I just thought that I could live with how it is after annoying one cylinder idling problem.
    do you, glider, think that this idle increasing can be related with this wrong setting on idle mixture adjustment?
     
    Last edited: Jun 24, 2008