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Thread: Scooter won't start -- fuel vaccum?

  1. #1
    Error No usernames avail

    Scooter won't start -- fuel vaccum?

    My scoot seems to be hurting in the recent days. It's been sitting in a warm garage since around October, ridden only about 4 short times.

    Since then the battery has died, it won't even crank the engine once.

    At any rate, I hooked up the battery to a car battery I had lying around. It sounded strong trying to turn the engine but still didn't start.

    I proceeded to take everything apart, panels and all. I took the spark plug out, replaced that and connected the fuel tank again. Still, no starting.

    I checked all the fuel lines to the carb, they're not kinked and they don't have any holes.

    I'm pretty much stumped as to what it could be? Perhaps spoiled gas?

    I also gathered this from searching the forum

    <blockquote><strong><em>Quote:</em></strong><hr>I have posted about this before. There is a valve on the fuel tank that is vacuum operated. Which means under low vacuum it closes, it is spring loaded also so this is the problem. When you start the scooter it doesn't create enough vacuum at times to open this valve and feed fuel to the injector. I take the vacuum line off and cut it and put an inline vacuum check valve or "one way" valve. Problem solved forever.[/quote]

    When I took off the fuel lines just a little fuel came out. I'm assuming this must be my problem(there is fuel in the tank), I'm just not sure how to remedy it.

    Any help would be greatly appreciated, spring is approaching and that means riding again!

  2. #2
    Error No usernames avail



    Any ideas on how to solve what I think the be the problem (no gas from the tank to the lines)

  3. #3
    Dutch Royal T

    Re: .

    every time you kickstart a little bit of fuel should come out.

  4. #4
    tiba karotsu

    Re: .

    it could be clogged (fuel filter), the diaphragm is leaking so it won't let fuel flow.

    try this get the vacuum hose that came from the fuel pump (is it a vacuum operated fuel @#%$?) and suck it and see if there's fuel flowing out of the gas lines. also try blowing compressed air to the gas lines as there could be gunk clogging up the inlet inside the gas tank.

  5. #5
    Error No usernames avail


    Ok, well I tired kicking it until I couldn't press down any more. It still wouldn't start

    I think I found my problem. Fuel is flowing to the carb but it's older fuel. I took the tank off and drained it.

    I'm assuming that the old volatile components of the gas got gooey and clogged up one of my starting jets.

    This is just my guess, as I know very little about carbs.

    I'm going to attempt to remove my carb and clean it. Got my fingers crossed

  6. #6


    Okay, one more time, find the small diameter vacuum line that goes to the front of the carb. No fuel should come out of this line. Pull it off the carb and suck on the end of it, yes that's what I said, suck on the vacuum line. This should open the fuel valve and fuel should rush to the carb.
    I can't believe no one can figure this out. I have had to do this to several friends scooters as they don't ride often or rev the engine like it should be reved. The valve is the silver piece that sits on the bottom of the tank. If you were top take the bodywork off you would see it. You can use a vacuum pump also if you don't want to suck on the hose. Micah, please explain to these guy's what I am talking about. Maybe you could take a picture of the valve and post it.

  7. #7
    Error No usernames avail


    I'm fairly convinced that the problem isn't fuel flow. There was fuel in the lines when I pulled them off, and once again after I put them back on (and pulled them off)

    I'm assuming the gas is broken down and clogging the starting jet.

    I tried taking off the carb and a stream of radiator fluid shot into my face. Gotta drain it and try again this weekend.

    I think I'm goign to take Dutch's advice and just tie 1 hose to both of the holes on the top of the cylinder and cross my fingers that it doesn't overheat

    The scooter looks so bare with only the front panel that houses the light on it.

  8. #8
    Dutch Royal T

    Re: .

    Error no names, didn't you mean to post that reply in this topic:

    Because there is where I told you to loop that line. Don't worry, looping is how everyone does it and doesn't affect the cilinder at all.

  9. #9
    Error No usernames avail


    oops, forgot about that topic.. haha.. I saw Foxster's reply and just threw it here.

    Thanks for all the help, hopefully this weekend I can get it running again!

  10. #10
    Error No usernames avail


    Woo! Success!

    After spilling nearly every liquid contained within the scoot on my garage, it's finally running again!

    I got the carb off and drained out the fuel that was sitting in there. A click blow on the jets and then a spray of carb cleaner did the trick.

    A few kicks and it started right up, a sound I hadn't heard in months

    Now the fun part, putting all the plastics back on :x

  11. #11
    apriliaforum newb
    Join Date
    Jun 2017

    2004 Mojito 150 vacuum problem

    This thread helped me so I wanted to post some pictures of the vacuum hose in case others have a similar problem.
    My hoses were dry rotted and cracked causing a vacuum leak. My 2004 Mojito 150 was unable to start because of the vacuum leak.

    In the diagram attached, 35 is the fuel cock and 23 is the fuel pump.

    It very helpful to me when people post pictures(you know what they say about pics vs words).
    Hope this helps someone.

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  12. #12
    apriliaforum newb
    Join Date
    Sep 2017
    New Hampshire
    Pete - I just stumbled across your post and it was exactly what I needed! The pictures really helped, thanks!

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