How-To: Diagnose Motorcycle Vacuum Leaks


  1. 0
    Posted 12/07/2014 at 7:34 | Permalink

    I just bought a 81 cb650. That looks like what you are working on here. I
    am having a cylinder misfiring type of issue. Could the vacuum leak be what
    is causing that? Also it doesnt want to run higher then 5k when under load.
    Any advice would be much valued. Thanks!

  2. 0
    Posted 12/07/2014 at 8:17 | Permalink

    This could be a dumb question, but I was told that you should avoid getting
    carb cleaner on gaskets and o rings and stuff because it would ruin the
    rubber in some way. Is this just fake or is it a different case with the
    rubber boots? Thanks!

  3. 0
    Posted 12/07/2014 at 8:38 | Permalink

    Hey what’s the average life of the rubber boots? I reckon I has the same
    issue but boots look excellent I have 2007 Ninja 250, the RPM hangs nearly 3,000
    and drops back to idle. Has over 7,000 miles.

  4. 0
    Posted 12/07/2014 at 9:29 | Permalink

    You are awesome man! Thanks for what you do, including answering peoples
    questions in the comments.

  5. 0
    Posted 12/07/2014 at 9:49 | Permalink

    thanks man…will the idle rpm always drop with a vacuum leak ? or does it
    sometimes rise ?

  6. 0
    Posted 12/07/2014 at 9:56 | Permalink

    the bike sounds wonderfillll after you place the new boots on buuuuut wheres
    the video on how to replace the boots ?

  7. 0
    Posted 12/07/2014 at 10:09 | Permalink

    Hey. I keep having a spontaneous backfire on my cb900 with a twin exhaust.
    I have had the carbs off and didnt change the boots. But I did this
    test and there are no leaks. Fuel is new , jets are sterile. Plugs have been
    swapped nearly, but the problem is staying at the right side. I have also
    synced the carbs.

  8. 0
    Posted 12/07/2014 at 10:42 | Permalink

    Even the RPM got higher after replacing these parts!

  9. 0
    Posted 12/07/2014 at 11:05 | Permalink

    Thx for the video. It was really helpful. I recently installed a
    hyper-charger on my 2005 vn800. I couldn’t figure out why it seemed to idle
    at different speeds. Now I highly suspect I have a vacuum leak in the

  10. 0
    Posted 12/07/2014 at 11:28 | Permalink

    Possibly. Check out my CB750 vacuum leak video where I take it for a spin.
    If you have the same symptoms, then yes you have leaks.

  11. 0
    Posted 12/07/2014 at 11:50 | Permalink

    please help i need help urgent,my email is

  12. 0
    Posted 12/07/2014 at 12:01 | Permalink

    I would check compression, place in new plugs, check timing if applicable,
    sterile carbs, check for vacuum leaks, synch carbs, and tune pilot fuel

  13. 0
    Posted 12/07/2014 at 12:40 | Permalink

    Are the boots expensive to replace?

  14. 0
    Posted 12/07/2014 at 13:37 | Permalink

    Can you help me identify the problem I’m facing with my motor? There’s a
    weird noise emanating from my engine. And it’s driving me idiotic. The
    video’s title ‘noise – suzuki gs550′ The video’s a bit dark, red bike.
    Thanks by Aaron Lee

  15. 0
    Posted 12/07/2014 at 14:03 | Permalink

    Check for leaks and assess pilot screw adjustment.

  16. 0
    Posted 12/07/2014 at 14:46 | Permalink

    My tale.Like i said RTV its a quick and fleeting fix till i replace them
    with new ones.Thanks again :)

  17. 0
    Posted 12/07/2014 at 15:17 | Permalink

    Yeah, tell me about it!

  18. 0
    Posted 12/07/2014 at 16:04 | Permalink

    i replaced valve shims on my bmw f650st,also cleaned bike wont
    start and i can hear a sucking sound from the carburator.what could be the

  19. 0
    Posted 12/07/2014 at 16:40 | Permalink

    Thanks for the answer…will check those things. I’ve noticed bike over-revs
    when early from cold but doesn’t do it if I start the bike when the
    engine is warm……ah! the joys of dirt bike maintenance!

  20. 0
    Posted 12/07/2014 at 17:23 | Permalink


  21. 0
    Posted 12/07/2014 at 18:23 | Permalink

    Sounds like a excellent plot. Let me know how it works out.

  22. 0
    Posted 12/07/2014 at 18:56 | Permalink

    thats what my dad said haha was just getting a second attitude thanks.

  23. 0
    Posted 12/07/2014 at 19:20 | Permalink

    Fantastic, informative video. Thank you.

  24. 0
    Posted 12/07/2014 at 19:35 | Permalink

    Does it stumble and die? What do the plugs look like? It probably is not
    getting fuel due to a plugged passage in carb or massive vacuum leak.

  25. 0
    Posted 12/07/2014 at 19:48 | Permalink

    Have you tartan timing, compression, valve adj? What does the plug look