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possible card stuck open

Discussion in 'XJ Technical Chat' started by burger, Aug 20, 2013.

  1. burger

    burger Member

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    My bike all of a sudden wants to idle at 4000 rpms. I think one of the carbs may be stuck open or something. The throttle and chock cables are both fully released. I believe it is the #3 cylinder because when you remove the spark plug boots #3 is the only one that makes a huge difference in engine speed. Am i going to have to dig into the carbs? I have been told that yamaha ringfree works amazingly on carbs if you run some through your gas, i may also run a little bit of that through but i don't wanna annoy my neighbors too much. Any other ideas that dont require rebuilding the carbs
     
  2. ecologito

    ecologito Well-Known Member

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    When is the last time you checked your valve shims?

    I keep reading about idling high and it could be a vacuum leak leading to cylinder 3.

    If you have not gone through your carbs you will never know what is wrong without eliminating one variable at a time.
     
  3. burger

    burger Member

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    I checked all my valve clearances about 3000 miles ago. Sprayed carb cleaner around the boots but no change in engine speed. Then turned engine off, pryed down on little cap on top of carb boot from carb to engine. stared it up again and now it runs fine, although i didnt run it long. I reved it a few times and it went back to normal idle. Could that small cap on top of the carb have been leaking?
     
  4. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    It most definitely could have, and would explain why unhooking the spark lead from the #3 plug slowed the engine down to idle. Excellent job on diagnosing, and solving, your problem. I would go a step further and replace the vacuum caps to prevent further problems in that area.
     
  5. mlew

    mlew Well-Known Member

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    I would say that cap had a vacuum leak, time to replace them all. If one was cracked the others are not far behind it. When checking for vacuum leaks you need a flammable substance. Some carb cleaners are non flammable and that's why you did not pick it up. I always use starting fluid or propane, they never fail me.
     
  6. burger

    burger Member

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    ok thanks. ill inspect the caps better and look into replacing them
     
  7. ronha13

    ronha13 Member

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    can I use an unlit torch to check for leaks in my carb boots?
     
  8. jmilliken

    jmilliken Well-Known Member

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    Ronha13. yes you can use an unlit propane torch
     
  9. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    REPLACE THEM. The may "look" fine but are usually rock-hard and no longer sealing properly.
     

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