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MikesXS slider carbs leaking

Discussion in 'The Garage' started by cmills83, Mar 4, 2019.

  1. cmills83

    cmills83 XS650 Addict

    I am trying to figure out why these carbs, specifically the left one keep randomly dumping gas all over the place. I've adjusted the floats, visually checked the float stops the flow of gas when it is in the up position and even tried replacing the floats but no luck.


    Every time I take off the bowls and move the floats around the bike will be fine for 5 - 10 miles or so then randomly I'll pull up to a stop light or park and look down to see at least one carb is leaking gas out of the bottom overflow hose. It seems to be after either riding for a while without stopping or forgetting to turn on the petcock, anything to cause the fuel level to drop in the carb. Once in a while it will stop on it's own, sometimes a quick tap with my hand will stop it, other times I have to take the bowls off.

    Has anyone experienced anything like this with these carbs? Or is there something besides the floats I should be looking at here? Thanks
  2. 650Skull

    650Skull Dinosaur Lives Top Contributor

    grizld1 likes this.
  3. cmills83

    cmills83 XS650 Addict

    Thanks yeah I unfortunately did my research after buying when I was struggling with the jetting. Reached out to MikesXS and they just said they leak sometimes. Sometimes is fine but not all the gd time.
  4. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    I don't have those carbs but have been through some fun with "real" VM's also. One area that the offbrands tend to cheat at is the accuracy of the float pivot. A float that is sloppy on it's pivot pin, can easily hang up or jam crooked and quit doing fuel level duties.The set that gave me overflow problems finally settled down when new float valves went in. Even though the parts in there "looked good".
  5. cafetools

    cafetools XS650 Addict

    Your needle valve spring is Lilley sticking. Or your float pin/ axle is binding.
  6. cmills83

    cmills83 XS650 Addict

    Ok thanks for the feedback. The floats seemed ok, I just pulled them apart and cleaned everything yesterday. They moved freely. The carbs have about ~250 miles on them and the new floats I put in a few weeks ago maybe 50 miles. Is there a another way to tell if the pin is sticking? Or is there a way to test if the valve spring is sticking? Or just I just start replacing things til it works?
  7. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    New fuel lines, CLEAN gas tank and fuel source? Yeah mikes carbs have a bad rep but it can be a problem upstream....
    Moabite likes this.
  8. grizld1

    grizld1 Grumpy old man Top Contributor

    Now there's some first class product support: "They leak sometimes." Translation: "These things are screwed up, we know they're screwed up, and we sell them anyway because we can." OP, "sometimes" may be OK with you, but it isn't OK with me; leaking fuel is a dangerous condition that needs to be corrected.
  9. cmills83

    cmills83 XS650 Addict

    I finished this build around 600 miles ago and the tank was re-sealed. I replaced the lines/filter with the carbs around 500 miles ago. I will go ahead and replace the lines/filters again. Only other thing is I'm running 1 petcock to a fuel tee, I've thought about installing 2 petcocks but not sure if that would really make a difference since the bike seems to be getting enough fuel.

    Just so I understand how would a possible dirty filter or clogged line cause the carb to leak fuel?
  10. cmills83

    cmills83 XS650 Addict

    Once I clarified it was during riding they emailed offering to send a replacement carb body so they are trying to fix it. I just want to make sure it's nothing on my end first before exchanging it.
    gggGary likes this.
  11. xjwmx

    xjwmx XS650 Guru Top Contributor

    Crap making it between the valve and seat holding it open.

    The good news here is they can seal, since it doesn't leak sometimes. Makes me think things are just misaligned. Maybe bush between the float and pin to take out the slop? Also...can make a very small bevel around the top of the seat so the valve is coaxed down into it rather than sticking cocked sideways.
    gggGary likes this.
  12. 650Skull

    650Skull Dinosaur Lives Top Contributor

    Offering a replacement for a sometimes leaking carb without any diagnostic from their tech dept tells a story on its own.........they know there is a problem.

    It shouldn't be able to..........if the filter element has broken then yes a bit, (more likely a built up pile of dirt will get through), of dirt can cause the carb float valve to lodge open.......... but also clog a jet and this would end up being a starving issue problem........But the effect of a clogged filter or line pre filter will starve the carb of fuel not create a leak...........
  13. cmills83

    cmills83 XS650 Addict

    I see, I'll replace the lines/filters for the hell of it but I did pull apart and clean both carbs a few days ago and they looked clean.
  14. copernicusdan

    copernicusdan XS650 Member

    I have those carbs, make sure slides are dropping, my throttle cable gets stuck sometimes, one of the cables where the 2 go into one get messed up, not sure if they got over pulled once, but every now and then then I have to pull tank and check it, think I may need to replace throttle cable
  15. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    Look at the float pivot/ pins, how sloppy are they? 2M went around this on the stock BS38 carb floats, the genuine floats have a bored brass pivot sleeve that the pin fits in, on aftermarket floats the bracket is just bent around the pivot pin.
    TwoManyXS1Bs likes this.
  16. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Not sure if this applies to yours, but you want to ensure that the float tang is perpendicular to the float valve. If at an angle, the valve can be pushed aside, bind, and hang-up before seating.


    The ways to adjust this are:
    - The length of the valve plunger
    - The seating depth of the valve body
    - Reforming the tab, maybe an "S" bend...
    Last edited: Mar 6, 2019
    joeluvs2fish likes this.
  17. cmills83

    cmills83 XS650 Addict

    Thanks, I see what you mean. The float tang is almost flat on both carbs. If anything I should probably bring it a little lower so the pin has more movement but both carbs are set the same just one is being a pos.
    TwoManyXS1Bs likes this.
  18. 5twins

    5twins XS650 Guru Top Contributor

    If you move the tang, you change the float height and fuel level in the bowl. You don't want a huge angle on the tang like in 2M's pic. That's what can jam things up. Your almost flat tangs are good. It's the carbs themselves that are poorly made and there's really no fixing that.
    TwoManyXS1Bs likes this.
  19. cmills83

    cmills83 XS650 Addict

    Yeah, got it. I am thinking I might drop it a little bit lower, as long as it still stops the flow of gas, maybe more movement in the pin will keep it from getting stuck. If not probably just exchange it. The other carb seems fine with the same settings, I think it has leaked once or twice maybe.
  20. copernicusdan

    copernicusdan XS650 Member

    float height is 19mm, if its still leaking check slides and make sure its not stuck open, pull carb off boot and look in there it should be down, make sure their moving up and down and not getting stuck

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