1. Dismiss Notice
  2. Dismiss Notice
  3. Hey Facebook people... We've created a group for XS650.com members to connect. Check it out!
    Dismiss Notice

Carb slides slightly askew

Discussion in 'The Garage' started by Marlin72xs, Nov 12, 2018.

  1. image.jpeg 2M, I've already put them back on the bike, but I cud try it in the 75 carbs. Almost certain that is where it hits. I feel like the Grandfather in "Moonstruck", "I'm so confused!"

    5Twins, since the long ones available, they could prolly be shortened on a lathe, eh? I'm not home now, but they just need to be sticking up, an 1/8" or so, in order to Bernoulli the gas up into the airflow. Those cuts look pretty easy.
     
  2. 5twins

    5twins XS650 Guru Top Contributor

    16,751
    5,706
    688
    I'm not sure they could be. The metering orifice may be right up near the top. You'd have to compare a "long" and "short" side by side to see. The metering orifice is the "step" you see when you look down into the top of the jet. It's usually about 1/8" down in there. You may end up cutting it off if you tried to shorten the long jet.
     
    TwoManyXS1Bs likes this.
  3. Yup, side by side comparison.

    2m, went back to the JBM site and took a closer look. The rubber section that hugs the slide is about 3/16" thick. So it should fit between the 2 lips and act as a stop. That should hold even without crazy glue. Wish I saw this site 1st, then i wouldn't have destroyed the top of my slide. Something tells me that i won't need the lip anyway. Replacement bellows are looking real good now.
     
  4. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

  5. 650Skull

    650Skull Dogonit Top Contributor

    TwoManyXS1Bs likes this.
  6. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    From one of the other links supplied by 650skull, a pic down the slide bore of bluebikerblan's carb, showing what I suspect is the stop ledge for the slide.

    BS38-SlideStop.jpg
     
  7. Been messin with the naked slide and bellowed slide with the 75 carb. Yes I see the shelf that it sits on. Those JBM diaphragms are looking good to me. But I have over problems.
    Just came in from the garage. It's about 39 degrees and windy. It kicked over real easy. Idled great with the choke on. Went for a test ride, shut off the choke in about 500ft, still OK. Coming to a stop and it wants to stall. Decided to turn uphill, just in case. Wouldn't idle at lights without coaxing. Went home and turned the low speed out to 1-1/4 from 3/4. Ride again and it takes about 10 seconds to idle down. Very weird. It didn't stall anymore, but would hang at 3K then slowly idled down. Went home and messed with the low speed again and 1 turn was better.
    I will pull the carbs tomorrow, but here's what I noticed. Put my hand behind left pipe and felt a good rush of exhaust. The right was weak. Turned the left down and right up and still the right was weak.
    OK, the left pipe was cold at the end, the right pipe was warm, a lot warmer. Keep in mind it's 39 degrees.
    In fact, I could touch the left pipe to the bottom of the header. The right was hot half way up the muffler. Pointed my heat sensor at the head just above the spark plug, ready, left was 130 somethin and the right was 230 somethin. Thought you guys would like this. Also checked the timing and it is exactly where it was when I installed it last June.
    I'm gonna sit back and read the very excellent carb PDF again and try to sort this out. Would appreciate any suggestions as I hope to take a 160 mile ride to see my son in Black Mountain, NC.
     
    Last edited: Nov 16, 2018
  8. gggGary

    gggGary Horsepower; just noise 'til the tire hooks up. Top Contributor XS650.com Supporter

    (re)check your ignition? Strength of spark and timing, both sides. If nothing else to eliminate ignition as the issue.
    Recent compression tests?
     
    Marlin72xs likes this.
  9. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    A quickee shop method, if using point ignition, is to blip the throttle, keep the revs up a bit, and pull a plug cap. Now running on one cylinder. I can feel the carb responses to throttling.

    While still running, replace the plug cap, and pull the other. Feel the other cylinder's carb responses, if any. Compare.

    Can do similar things with unlinked carbs. Left and right hands on left and right carb levers. Blip each independantly, listening and sensing the differences...
     
    Marlin72xs likes this.
  10. Well, I have a pamco, so I'll have to make up some large clips to ground the plugs securely. NP. I might need a new compression tester, but that is a good idea. Going to bed now. Will think about this more tomorrow. Thanks guys.
     
    gggGary likes this.
  11. gggGary

    gggGary Horsepower; just noise 'til the tire hooks up. Top Contributor XS650.com Supporter

    Test floats for leaks? (hot water dip test)
     
    Marlin72xs likes this.
  12. I will certainly try that, thanks. Does anyone have a theory on why the strong side is cold and the weak side is hot?
     
  13. gggGary

    gggGary Horsepower; just noise 'til the tire hooks up. Top Contributor XS650.com Supporter

    Carbs are way out of synch?
     
    peanut and Marlin72xs like this.
  14. 5twins

    5twins XS650 Guru Top Contributor

    16,751
    5,706
    688
    That is odd. A cold pipe usually indicates that side isn't firing. But yours is a little warm so maybe you're just not firing 100% of the time. But one cylinder not firing is odd with a Pamco and/or a dual output coil. That type of coil fires both plug wires at the same time and every time (wasted spark). If the spark is intermittent on one cylinder, the cause would have to be the plug, plug cap, or plug wire on that side. There are some easy checks you can do. Swap the plug wires side to side and see if the cold cylinder changes sides. That will show you whether it's ignition or carb related. Swap the plugs side to side and look for the same change.
     
    mrtwowheel and Marlin72xs like this.
  15. Since the 750 upgrade, i can turn the throttle stops all the way out and it still idles at around 1200. I didn't mess with the cables, so it should have been fairly close. I will double check that.
     
  16. 5twins

    5twins XS650 Guru Top Contributor

    16,751
    5,706
    688
    It seems your butterflies aren't closing all the way. Backing the idle speed screw out all the way so it's not even touching the cable lever should close the butterfly completely and stall that cylinder. Did you replace the butterfly shaft seals? If so then maybe you don't have the butterfly plates centered properly. Or, maybe your throttle cables are too tight. If they don't have enough freeplay in them, that could hold the plates open when you back the adjustment screws out.
     
  17. gggGary

    gggGary Horsepower; just noise 'til the tire hooks up. Top Contributor XS650.com Supporter

    Synch two cable carbs on a regular basis. At the very least each time the tank has been removed. Any slight change in cable routing will change the synch. Big part of why linked carbs were introduced. Hands over the mufflers can be accurate with experience, I've verified that method with vacuum gauges.
     
    Superjet and Marlin72xs like this.
  18. 5twins

    5twins XS650 Guru Top Contributor

    16,751
    5,706
    688
    Syncing dual cable carbs is a 2 step process. First you must set and sync the idle speed between the 2 carbs, then set (sync) cable freeplay on each one( match it between the 2). You must set the idle speed first because adjusting it changes the amount of freeplay in the cable.
     
    Marlin72xs and gggGary like this.
  19. I will try all that and i have a new set of plugs to try. A plug reading may give me some clues also. I have a Harbor freight compression leak tester that i will also give a try. In my head i keep thinking the worst, like burnt exhaust valve. But on the bright side, i cud have merely moved a piece of dirt to another spot in the carb or i loosened a spark plug wire putting the tank on. Thanks.
     
  20. I usually leave a lot of free play in my throttle cables as a rule, but will also recheck.

    Oh, and Gary, when I first noticed the difference in exhaust flow, I tried raising the idle and over adjusting the cables, but no change. Again, on the bright side, it's gotta be somethin simple. Otherwise, my simple mind won't get it. Thanks again.
     
    gggGary likes this.

Share This Page