California bike, vapor lock?
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  1. #1
    Senior Member jontow's Avatar
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    My bike is a 97 california model; with the funny charcoal canister tank vent.



    If I sustain 50+mph or wind it out a bit (climbing hills is an easy way to do

    this, as you all know) it'll just start stuttering for a few seconds and then

    just quit. It happened to me the first day I rode it and I ended up pushing

    it home because it wouldn't start back up; it then started 1/2 mile from the

    house like it hadn't ever happened.



    Today, I was able to reproduce it twice on the same road (with a really large

    valley in it, going up the hill both ways, within 500ft from eachother). I

    decided to try just moving the petcock back and forth from 'ON' to 'RES' a few

    times, and it just started right up after that.



    My theory is that the canister or one of the lines to/from it is plugged,

    probably the third equalizing one so that its always drawing a vacuum on the

    tank, and at high rpms I presume its drawing more vacuum than it can equalize

    and therefor starving it for fuel? It normally stutters and acts lean, even

    though I checked the screens up in the tank on the petcock inputs, and pulled

    and cleaned the carb out (was pretty clean already).



    Has anyone seen/had this happen on their bike? It acts a lot like a bike that

    someone noted in another thread (can't find it now) that ended up being a fuel

    issue but they originally thought it was ignition/electrical related, and they

    had replaced the CDI/stator/etc.



    Ideas? I'm gonna pull the canister apart and see whats up after I put the kids

    to bed, maybe I'll figure out my problem and I'll drop the details here if I do.

    Otherwise, I noticed the board is fairly active around 7-8PM EST, maybe someone

    knows the answer for me and I'm looking in the wrong spot.
    --

    1997 TW, well loved, a bit modified.

  2. #2
    Banned qwerty's Avatar
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    First off, vapor lock cannot exist in a fuel system that is vented to atmosphere, which ours is. If fuel vaporized in a fuel line or passage on a TW it would simply flow up the fuel line into the tank. It is difficult to run a siphon system from an auxilary tank to the carb because air bubbles often find their way from the float bowl, past the needle and seat, and into the fuel line. That is why a fuel filter on its side will always have air in it.



    Sounds like a fuel flow problem. If the screen under the lever in the petcock, the lines, and the carb are all clean, it can only be one of four things. First, make sure the fuel line is not kinked. Second, make sure the lines to the charcoal canister are not kinked or plugged. Third, pull the lines from the canister and run the bike. If the problem recurs, the canister isn't the problem. If the problem goes away, the canister has a flow problem. Fourth, there are screens hooked to the petcock inside the tank that can be stopped up. Remove the petcock to check them.




  3. #3
    Senior Member lizrdbrth's Avatar
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    That poor canister is nearly 99% foolproof, yet gets blamed for everything but the Lincoln assassination. Unless by some weird occurrence the carbon got broke up inside it and clogged a line I doubt it's causing your problem.



    The canister doesn't subject the tank to vacuum in any way. If it did, your bike would never run in the first place. It's just a third carb vent, the same as the other two on your float bowl, and is always at atmospheric pressure. The only difference between a Cali bike and the other 49 states is that the tank vents through the carb rather than the fuel cap.



    You are correct that if it gets clogged it could cause the tank to cavitate, much like an upside-down gallon milk bottle would "glug" its contents out, rather than flowing smoothly. You can check it by disconnecting the hoses at the carb and under the tank and blowing through them. Air should pass, both directions. If it does, you have another issue.



    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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  5. #4
    Senior Member jontow's Avatar
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    Sorry if I put blame in the wrong spot. I had a chance to take a look at the bike after

    I read the replies. I think I probably misunderstood the way the canister operates.



    There are 3 hoses going to it, one from the tank (tested with air blown clear through it,

    no restriction), another from the canister to the carb (also clear), and a third at the

    bottom thats just open to the atmosphere. This one was plugged with dirt/mud, and I've

    cleared it out now.



    With one of the clear hoses hooked up and each of the other openings plugged off individually,

    air can pass through the canister, though with plenty of restriction. This could easily be

    considered normal, since i'm assuming its a charcoal type filter, so lots of tiny holes to

    have to push air through.



    Would the bottom open hose being plugged cause this particular issue?



    Now, a few directed replies: the other day when i first was looking at the fuel system, I had

    pulled the lever off the petcock and fuel VERY readily flowed through it.. all over my driveway,

    of course i did pull the petcock out of the tank at that point and the screens were clear,

    there was no screen in the petcock assembly itself as I've heard described.



    The fuel line is very short and certainly not kinked; it does not currently have a filter inline,

    but the tank is fairly clean and I am avoiding adding one until I've tracked down my issues.



    No lines are kinked, and only the one was plugged. It's a bit late now to anger the neighbors

    by winding it out on the closest large hill, and I don't feel like hitting a deer; so I'll test

    my change tomorrow on my way to/from work to see if I can repeat the failure.



    Thanks for the fast replies, we'll see how the suggestions helped in the morning!
    --

    1997 TW, well loved, a bit modified.

  6. #5
    Senior Member jontow's Avatar
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    Just thought of a few more things:



    Could the float being adjusted too low cause this so severely..?

    If the lines from the float bowl vents plug, same deal?
    --

    1997 TW, well loved, a bit modified.

  7. #6
    Senior Member thumper's Avatar
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    Quote Originally Posted by jontow View Post
    Just thought of a few more things:



    Could the float being adjusted too low cause this so severely..?

    If the lines from the float bowl vents plug, same deal?


    I know whats wrong with your bike! I'm really surprized nobody else thought of it before I had a chance to post the answer

    You were close with the vapor lock idea (but no cigar)

    Its not the canister, but the gas cap! Its very common for these bikes to create a vacume with run really hard at high RPM

    or when run down hill or a long grade, they stutter and do the same thing.

    Simple remove the cap, wipe the tank off, and blow some compressed air into the tiny little pin hole that you'll find underneath

    the cap.

    This should fix 'er right up!

    Don't over think this too much.

    Ride safe, hope this helps.

    Igofar

  8. #7
    Senior Member lizrdbrth's Avatar
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    Cali gas caps don't vent.



    There's an internal tube routed through the tank leading up into the filler neck area, which is vented to the atmospjhere through the carb vent. The canister contains fumes coincidental to the venting.



    The third line leading to the ground is a drain. If you dropped the bike it would prevent liquid fuel from remaining in the canister.



    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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  9. #8
    Senior Member srs713's Avatar
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    Quote Originally Posted by jontow View Post
    Sorry if I put blame in the wrong spot. I had a chance to take a look at the bike after

    I read the replies. I think I probably misunderstood the way the canister operates.



    There are 3 hoses going to it, one from the tank (tested with air blown clear through it,

    no restriction), another from the canister to the carb (also clear), and a third at the

    bottom thats just open to the atmosphere. This one was plugged with dirt/mud, and I've

    cleared it out now.



    Would the bottom open hose being plugged cause this particular issue?


    The bottom one is the hose that kills the bike if you get too deep in a water crossing (as per another thread).



    Plugged, it probably would affect the bikes performance.
    Stephen S.

    '07 TW200:

    15/50 sprockets, O-ring chain, D2Moto foot pegs

    tweaked carb (127.5 jet, 0.019 needle shim, idle screw @2.25),

    Rubbermaid "Action Packer" on homemade brackets

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