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Idle Problems

Discussion in 'XJ Technical Chat' started by gaillarry, Oct 1, 2008.

  1. gaillarry

    gaillarry Member

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    81 Seca 750, just rebuilt the carbs, parts obtained from our friend on this site. Bike starts easily with choke' With the choke off it will idle at 1100 rpms. When I rev the engine the idle will return below 1100 rpms and the engine stalls.

    I removed the throttle cable and set the idle with the idle screw at 1100 rpms. Bike idles perfectly at 1100 but when I pull the throttle cable to increase the rpms the idle won't return to 1100. I've done this a dozen times and can never get the idle to return to the same setting.

    What am I doing wrong??
     
    gaillarry, Oct 1, 2008
    #1
  2. bill

    bill Active Member

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    Does it do better when warmed up? You want to set idle at operating temperature.

    Also with freshly rebuilt carbs you will have a bit of tuning to do. Check your plug with chops and do a sync. I found it was an iterative process tune- sync repeat...
     
    bill, Oct 1, 2008
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  3. gaillarry

    gaillarry Member

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    I forgot I had a colortune in the tool box. Just used it and got all the readings to a gas color blue flame. One thing I didn't do was bench sync the carbs !!! Time to pull the carbs again.
     
    gaillarry, Oct 1, 2008
    #3
  4. bill

    bill Active Member

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    Bench sync gives you a good starting point - you will want to sync on the bike for fine tuning. Good luck. The colortune is great I have one - I use it as a starting point then have been reading my plugs...
     
    bill, Oct 1, 2008
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  5. RickCoMatic

    RickCoMatic Well-Known Member

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    Spray the Manifolds and Throttle Shaft Seals with some Carb Cleaner while the Engine is running.

    If the RPM's rise. You have Air Leaks to contend with.
    Spray:
    Where Manifolds seat to Cylinder Head
    Bodies of Manifolds
    Where Carb Intake Necks seat into Manifolds
    Throttle Shaft Pivot Points -- Both sides.

    What happens to the RPM's when you spray them?
    Report the findings.
     
    RickCoMatic, Oct 1, 2008
    #5
  6. gaillarry

    gaillarry Member

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    Using the colortune and reading the spark plugs I got the bike to idle and return to the proper idle. Runs great now, thanks for all the info.
     
    gaillarry, Oct 1, 2008
    #6
  7. MiCarl

    MiCarl Active Member

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    While on this subject.

    I have a ROKETA motorcycle in my shop (don't buy one).

    Problem with it was if rev engine and release the throttle it'd drop through the idle and stall.

    Turns out the exhaust valve was too tight. The heat from revving lengthened it enough there wasn't enough compression left for the bike to idle.

    Just over 600 miles in it and there was 0 (or less) valve lash.
     
    MiCarl, Oct 1, 2008
    #7

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