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REPETE'S XS650B Preservation Carburetor

Discussion in 'The Garage' started by REPETE, Oct 31, 2019.

  1. 5twins

    5twins XS650 Guru Top Contributor

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    You might want to do an external fuel level check using a clear tube. The fuel levels in your float bowls may be off, lower on the lean running side and/or higher on the rich side.

    [​IMG]

    [​IMG]

    [​IMG]
     
    TwoManyXS1Bs likes this.
  2. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    5T -
    I did buy that tube - just never followed through with it. :(
    I'll put the bike back up on the lift and check the levels with it. Seems easy enough.
    Makes sense before continuing with the minuscule turning of the mixture screws every time I test ride.
    So, the thread isn't "officially" dead yet.
    Good thought!

    Pete
     
    gggGary likes this.
  3. Rasputin

    Rasputin XS650 Addict

    You really need to know whereabouts the mixture imbalance is in the Rev range. I would suggest doing a plug chop after an uninterrupted steady mid throttle for say 3 to 4 miles. Kill the engine and check the plugs then. If you let it idle or go onto the pilot circuit it will spoil the plug colour. If it still looks unbalanced you may check the starter jet plungers to make sure they or it are sealing properly. Just a thought.
     
    gggGary likes this.
  4. 5twins

    5twins XS650 Guru Top Contributor

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    Try to have the bike level and check both sides without moving it. I have a small brass wedge I can use under one of the centerstand legs to level it up. I place a torpedo level across the front motor mount.
     
  5. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    Also great advice!
    I have plastic jamb wedges I can use to level off.

    Rasputin the plug pics are after a long country ride followed by several miles of "city" light to light riding followed by idling at the gatehouse to my community. So the pilot circuit is in play with the coloration you're seeing. I'll do a "chop test" once I'm certain the floats are equally and properly set. They have been done and checked prior with a caliper (several times wheres the carbs were removed and torn down multiple times), but the liquid level will be the best indicator. The bike runs beautifully at 1/4 throttle and above.... smooth and responsive. It's the occasional "pop" and deceleration brabble I've been chasing and my concentration has been on the pilot circuit.

    Pete
     
  6. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    5T....
    For clarification.... you're measuring from the top of the carb body flange that the float bowl mates to?
     
  7. 5twins

    5twins XS650 Guru Top Contributor

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    The measurements in the pic labels are the normal measurements you take when setting the float height with the bowls off, carbs turned upside down. The measurement is taken from the carb body float bowl gasket surface, not the raised lip surrounding it, like so .....

    [​IMG]

    Notice the ruler is sitting down inside the lip, not on it.
     
  8. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    5T....
    I'm completely with you on the method of measuring the float heights and doing it from the recessed gasket surface. That's exactly how I did mine. Carefully and cautiously.
    But the pics you've provided determining the float height (your examples of 26mm, 28mm, etc.) have me confused.
    When using this liquid level method, is the target a known desirable fuel level that to me appears to be the joint between the bowl and carb body?
    I base this assumption on the last picture showing a properly set level. The liquid level is right at the joint. The only thing I've taken (and perhaps incorrectly) from the other two pics is that you're demonstrating the maladjusted float heights by showing the difference between the actual liquid level and the desirable liquid level... being the aforementioned joint since that is where it appears to me where you are measuring from.
    Can you clarify for me?
    Thank you.

    Pete
     
    Last edited: Dec 18, 2019
    gggGary likes this.
  9. 5twins

    5twins XS650 Guru Top Contributor

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    Yes, the "target" level is right around the seam the bowl makes with the lip on the main carb body. This puts the fuel level a couple MM below the top edge of the bowl since that top edge is actually up inside the lip a little bit. You don't want the fuel level at or above the top of the bowl or it will be constantly soaking into the gasket and may start leaking. It can also cause rich running if too high.

    The two low level pics are from a local guy's bike I worked on. The bike ran OK but was very difficult to start, hot or cold. This turned out to be the reason why. I'm guessing it was starving for fuel during the start process. The pics are from my initial clear tube check. The numbers are what I found when I took them apart and measured the float settings. With the ruler in the pic, I was trying to determine the relationship between the tube reading and the actual setting. It seems to work out to about 2 to 1. Being about 1mm off on your setting seems to show as about a 2mm difference on the tube. The one found set at 28mm illustrates this pretty well. That setting is 4mm off and the fuel level in the tube is sitting about 8mm too low.
     
    gggGary likes this.
  10. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    5T -
    Thank You for the more detailed explanation.
    I now have a clear target.
    I'll report back what I find.

    Pete
     

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