Honda Magna V30 won't start in cold wether

Discussion in 'Motorbike Technical Discussion' started by Seamus, Oct 24, 2006.

  1. Seamus

    Seamus Guest

    I entered a topic in the past regarding my bike not starting several
    weeks ago and all the great advice from users got it started, thanks.
    Anyway the problem at that time was the bike would not start at all.
    To make a long story short it was the carbs being pluged with old
    congiled fule. After cleaning out the carbs and setting the idle the
    bike ran great. By the way this was a complete tear down of the carbs.
    The choking system worked I know this because when it was about 40
    degrees I could start it with the choke and as it warmed I would
    release the choke partialy until the bike was warmed up. So that being
    said I was wondering what might cause the bike to start when the temp
    outside is around 30 degrees. That is the only difference so you know
    I started the bike twice a day to make sure that I ran a full tank
    through the system of fresh gas. The fule in the bike now is fresh so
    that shoudnt be the problem. Please let me know if you need any more

    Seamus, Oct 24, 2006
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  2. Seamus

    B-12 Guest

    Well, the engine needs to get a burnable mixture before the ignition
    spark can light the fire. In really cold climates, the gasoline just
    won't break up into fine droplets or evaporate, and that's when a lot
    of car owners resort to ether injected into the carburetor.

    It's hard to get ether into a motorcycle intake system, though. Too
    many parts to remove.

    But 30 degrees isn't that cold, the engine should start on gasoline if
    the idle mixture is set right and you put the choke lever into the ON
    position. If everything is set correctly, you shouldn't have to fool
    around with the throttle position, you should be able to put on your
    helmet and gloves without nursing the throttle or continuously
    adjusting the choke lever.

    Modern motorcycle carburetors don't have a real choke, with a separate
    plate that restricts air flow.

    They depend upon the throttle butterfly to restrict the air flow
    instead. There is a bypass passage that goes around the butterfly and
    it has a little valve in it that is opened and closed by the "choke"
    cable or lever. The bypass draws gasoline right out of the float bowl.

    The bypass passage is so big it doesn't get plugged up with gum and

    But the position of the throttle butterfly affects vacuum in the
    carburetor mixing chamber downstream of the butterfly. If the butterfly
    is too far open, the bypass system just doesn't work, and the rider is

    Old time British motorcycle riders knew what to do. Every time they
    started their engine after the machine had sat unridden for a week or
    so, they would turn the idle speed knob all the way down to close the
    throttle all the way and make the engine suck gasoline out of the float
    bowl. Then they would readjust the idle speed once the engine was
    warmed up.

    The throttle butterfly also has to interact with the idle mixture
    system. It barely covers the last in a triangular pattern of three
    transition ports, and the setting of the throttle butterfly is critical
    for good acceleration and correct off-idle performance.

    Possibly you didn't do a good enough job of cleaning out the idle jets
    and passages and there may still be a bit of crud in the carbs. I
    recommend pouring about 3 or 4 ounces of Berryman B-12 Chemtool Choke
    and Carburetor Cleaner in a full tank of gas and going for a slow ride
    to clean the passages out.

    If the engine starts idling too fast when it warms up. turn the master
    idle knob down.

    Believe it or not, this will help cold starting, because it increases
    vacuum downstream of the butterfly.

    Drilling out the EPA anti-tamper plugs and removing the idle mixture
    screws and cleaning the passage thoroughly with aerosol carburetor
    cleaner helps a lot. When you re-install the screws, leave them open
    about 1/8th to 1/4th of a turn more than the factory setting to make
    your machine easier to start.

    I have explained how to drill out EPA plugs about a bazillion times, so
    you can google that up.

    There is a very large difference in idle jet sizes amongst various
    motorcycles, so nobody can tell you exactly how many turns your idle
    mixture screws have to be from lightly seated. You have to count the
    number of turns they were set at the factory and write it down to
    return to the original setting plus a fraction of a turn, then you have
    to test ride the machine to see how the carbs behave when the engine is
    B-12, Oct 24, 2006
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  3. Seamus

    John Johnson Guest

    Does it idle smoothly?
    Is the idle adjusted properly?

    It might be a carb synchronization issue.

    Or, it might be a battery that gets marginal when it's cold (load-test
    battery, and you'll know for sure).



    'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.
    John Johnson, Oct 24, 2006
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