Honda 650 starting problems when very hot

Discussion in 'Motorbike Technical Discussion' started by jackd, Jul 20, 2006.

  1. jackd

    jackd Guest

    Hi: I own a 1981 Honda CB650 custom, 30,000 kms on it. one of m
    problems is after riding for a while, I cannot shut it off and have i
    restart again unless I wait about 5 -10 minutes. It barely cranks ove
    at all. After about 5 - 10 minutes, no problem. I have been told tha
    it is the coil and I have also been told to advance the timing a bit.

    While I am at it, I just had all the upper gaskets changed and sinc
    then (also when the bike is hot) I cannot sit at a red light and kic
    it into neutral. It will always go into second.I was told by th
    mechanics that they did not touch the bottom end of the motor. The onl
    thing I did was after I got it back, I changed the oil and did put to
    much in but I siphoned most of the excess out. Could too much oi
    cause this sort of a thing?

    Any info or comments would be appreciated. Thanks in advanc
    jackd, Jul 20, 2006
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  2. jackd

    MadDogR75 Guest

    Too much oil - not unless there`s an awfull lot of it.
    if it shows a reluctanct to crank, your problem is not in the ignition.
    If it cranks easily when cold, suspect some sort of temperature
    related friction. (probably serious).
    Did the cranking problem start right after the gasket work???
    Is your mechanic SURE that nothing got dropped into the lower
    Check the oil pressure hot & cold????
    MadDogR75, Jul 21, 2006
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  3. jackd

    FB Guest

    Your carburetors are getting plugged up with gum and varnish deposited
    by evaporating gasoline. Find a carburetor cleaner that contains
    xylene, acetone, toluene, methyl alcohol and the like.

    You can find such carburetor cleaners in aerosol cans in auto parts
    stores. Don't buy anything that says its especially for fuel injection
    systems, and don't buy anything that says it's carburetor dip.

    The stuff you want will be clear and colorless.

    Put 3 or 4 ounces of that stuff in a full tank and go for a slow ride
    so the mixture has to go through the idle jets and clean them out.

    Before you ride, find out where the idle speed knob is at, probably
    between the #3 and #4 carbs on the right hand side. After you ride a
    few miles, the idle speed will increase because the carburetor cleaner
    is working and you'll need to turn the idle down.
    That's a symptom of dirty carburetors. The idle mixture is too lean to
    start the engine when it's hot/
    Whoever told you that you needed a new coil is full of shit. If you
    needed a coil, the problem wouldn't just happen when you try to start
    the engine when it's hot.

    The idea of advancing the timing is really stupid. If you advance the
    timing too far and the engine gets too hot from lean idle mixture, the
    starter won't be able to crank the engine.
    OK, like I said, the engine is too hot because the carburetors are
    dirty and you aren't getting enough gasoline in the idle mixture. The
    heat expands all parts of the engine, including the clutch, you get
    excessive clutch drag and when you try to shift into neutral, the
    clutch doesn't disengage and you overshoot into second gear.

    Clean out the carburetors as I described above.

    You would be surprised at how much gasoline your engine wastes just to
    stay cool and keep from melting the pistons. if you can find the idle
    mixture screws (they are probably hidden underneath metal anti-tamper
    plugs) and turn them counterclockwise 1/4 of a turn, you'll be amazed
    at how much cooler yuor engine runs and how much more throttle response
    you have.
    Nope. Your engine would just slap out the excess oil and you might wind
    up with oil in the air box and an oily air filter. You cannot clean the
    oil out of a paper air filter.
    If you get a paper air filter oiled, you have to buy a new one.
    FB, Jul 21, 2006
  4. jackd

    RCFlyr Guest

    Could be a weak Battery if the engine barely cranks over. No more cheap
    batterys for me. Coil has nothing to do with the engine cranking over.
    Yep, did the same thing to my FT-500 Ascot. Couldn't find neutral until
    I drained the excess
    RCFlyr, Jul 21, 2006
  5. jackd

    fweddybear Guest

    I was thinking it could be a venting problem in your gas tank. Vapor
    lock maybe.... Have you tried starting it with the gas cap off when its hot?

    fweddybear, Jul 21, 2006
  6. jackd

    jackd Guest

    Jackd - Hey Guys: sorry about the delay in response - actually the n
    cranking issue was happening last year also. Only the fact that
    cannot get it into neutral started right after the gaskets wer
    changed. I have managed to get most of the excess oil out already. I
    seems like the battery is almost dead when it happens, but like I sa
    wait 5 minutes and bang it's cranking over again.
    I have not done the gas tank vent test but I will next time it happens
    I ran into an approx 70 year old woman who said she used to work o
    these bikes with her brothers way back and she (without any hesitatio
    or tips from me) said that it is a relay problem for the no crankin
    jackd, Jul 28, 2006
  7. jackd

    FB Guest

    Oh, yeah, Jack. Any time I have problems starting my motorcycles, I
    always ask
    Grandma what's wrong. ;-)

    If you had a starter relay problem when the engine is HOT, you'd still
    have a starter relay problem when the engine was COLD.

    Pay attention now. When the carburetors start getting plugged up, the
    idle mixture is too lean and the engine gets hot and the spark plugs
    get so hot the glowing electrodes will cause the cylinder to fire
    BEFORE the spark occurs.

    If the ignition is supposed to fire 10 degrees before top dead center
    cold, the pre-ignition might take place 45 degrees before top dead

    This radically increases the pressure in the cylinder and the starter
    has to work too hard and it can't turn the engine over. You get the
    impression that the battery is dead,
    but every thing works fine when the engine cools off.

    So, follow the carburetor cleaning instructions I wrote up last week.

    Or go ask Grandma for a glass of milk and a cookie.
    FB, Jul 29, 2006
  8. jackd

    hlblybowski Guest

    hlblybowski, Aug 7, 2006
  9. jackd

    hlblybowski Guest

    I have the same bike and the same problem. As for the starting problem,
    it's one of two things. the starter is bad or needs cleaned, or the
    charging system isnt working.
    I found my problem was the voltage rectifior was bad and not keeping
    the battery charged. As for the shifting into neutral, the clutch may
    be worn or out of adjustment. If you dont have one get yourself a
    clymer service manual(at any honda shop about $20) it is very detailed
    and gives step by step insturctions on how to test all this. Good luck.
    hlblybowski, Aug 7, 2006
  10. jackd

    Ron Seiden Guest


    At your local hardware store, in the paint department, it's called "lacquer
    thinner" -- it's cheap (with that label -- expensive if it's called "carb
    cleaner") and really is a witch's brew of solvents...
    Ron Seiden, Aug 10, 2006
  11. jackd

    FB Guest

    Can you get a pint of lacquer thinner for $2.90 at your local hardware

    I've never looked for that chemical specifically but I would bet the
    local Home Depot would charge me $4.50 to $5.00 for it. Orchard
    Hardware charged me that much for MEK.

    HD wants $8.00 a gallon for kerosene, and I would buy kerosene in bulk
    from a local
    gas station if I knew where there was one with a kerosene pump. I saw a
    kerosene pump in Salinas once. They were charging about $2.00 a gallon.
    FB, Aug 10, 2006
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