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Dodgey fuel tap

Discussion in 'Technical and Troubleshooting Torque' started by duff_boy, Jun 27, 2008.

  1. Hey guys.

    My lil bandit has been running a little average at lower revs(<4000) as well as being hard to start and i was just thinking, can a dodgey fuel tap cause it to run not so well? I was reading through the fuel system manual for my bike, and it makes mention of a vacuum diaphragm in the fuel tap, what this does it only allows fuel flow when the is low pressure created by the engine. Which means there should be no fuel flow when theres no vacuum.

    I just realised that when i have, in the past remove the tank, if i disconnect the fuel line, fuel comes streaming out. This shouldn't happen. Ive got a spare tank in the shed, i went out and checked and no fuel flow from the tap, but if i suck on the vacuum like it lets fuel past.

    I plan to swap the fuel tap tomorrow, but im just wondering, can i expect the broken current tap to cause any problems??? Also i noticed that the fuel tap has a inbuilt fine strainer/filter. My bike also has an inline filter. Since its gravity fed an inline filter shouldn't be used, yes? As it poses as a bit of a restriction, i will remove that as well.

    Anyhow, im not that good with the old school carbie systems and what not, so thanks for the help.
  2. No.

    Not without other symptoms, such as a pool of fuel on the floor overnight.

    Most likely cause of problem is:

    1) Bad valve adjustment - 4 cylinders get left by n00bs because of the expense

    2) Bad spark plugs

    3) Other stuff

    You seem to have answered all your other questions well.


    Trevor G
  3. I haven't gotten around to fixing my fuel tap (Runs in Off position), but have noticed no performance loss. It's just annoying to have to stop up the fuel flow when I remove the tank.
  4. Swaped the fuel tap and removed the inline filter today. While i was there i removed the airbox and gave it a good clean out, pulled the carbies down and gave all the parts a good clean/inspect. Sprayed carbie cleaner all through the internals. Then i started it up and sprayed it in as it ran.

    It was funny, i couldn't get it to start after i had put the carbies back together and connected up a fuel supply. I thought ok the fuel just needs to prime abit and kept cranking, and cranking, and cranking. Then i thought to myself. Wait a minute, the CDI is mounted on the back of the air box, which i removed and is sitting on the ground. Obviously not going to start with no ignition. So i pluged the cdi in, and cranked it again. BANG huge flame exploded out the back of the exhaust. very loud lol scared the crap out of me.

    Anyway, all in all it seems to idle/rev up abit better now. So ill take it for a ride later and see how it goes :).
  5. Why do we all want to share embarassing stories of our best goof-ups?? ;-)

    That was a good one - I'm glad both bike and ham-fisted repairer survived. (PS Always look for parts left over!)

    Psst - don't tell anyone, but I once made extensive mods to the slide on a carb which wouldn't run properly after I fitted it, only to find 3 months later that I had left out the pilot jet itself. No wonder it was running rich down low!


    Trevor G