My CB450 will not start no matter what.
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Thread: My CB450 will not start no matter what.

  1. #1
    Member ckemps's Avatar
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    My CB450 will not start no matter what.

    1974 Honda CB450 DOHC
    ALRIGHT BACK TO BASICS...There are only so many things an engine needs to run, spark, compression, fuel, and timing.
    Both carburetors have been rebuilt correctly and the correct amount of gas is flowing into the cylinders.
    Both cylinders have about 150+ compression.
    Both spark plugs are firing.
    The cam and crank have been timed together correctly after rebuilding my cylinder head, timing for the ignition is timed correctly to the compression stroke for both cylinders.
    The bike wont even fire up while I'm spraying starting fluid direct through the carbs (choked or not).
    Is there something obvious I am missing?? WHY wont this bike start!?

    thankyou all who respond i need as much insight as possible.
    Last edited by ckemps; 06-12-2019 at 07:41 AM.

  2. #2
    Senior Member Lefty's Avatar
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    Somethings not right
    Rob Axel and jd50i like this.

  3. #3
    Senior Member WintrSol's Avatar
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    Are you using the kick start, or electric? If electric, the Voltage may be sagging too low to get a strong enough spark, so try using a booster battery; if you jump to a car or truck do NOT start that vehicle's engine!
    Rick

    Mine is a mostly 1970 CB450K3

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  5. #4
    Senior Member pattyandrick's Avatar
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    The cam on the advancer could be 180 degees off

    Sent from my SM-J320V using Tapatalk

  6. #5
    Sensei 66Sprint's Avatar
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    What reference are you using to determine compression stroke for a cylinder?

    Has the rotor been pulled and re-installed?

    Please feel free to phone to complete this dialog.......
    Last edited by 66Sprint; 06-12-2019 at 03:22 AM.
    "I have a mind like a steel trap.....Old and rusty, of antiquated design, and hard to get stuff back out of...."
    Contact info: E-mail; [email protected] Phone; 540-525-5199

  7. #6
    Senior Member Rob Axel's Avatar
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    My question... was it EVER running???
    When?
    Then... what was done to make it not run?
    "Yes, my hands and nails have grease stains. I ride vintage!"
    -xulf13-

  8. #7
    Member ckemps's Avatar
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    Quote Originally Posted by WintrSol View Post
    Are you using the kick start, or electric? If electric, the Voltage may be sagging too low to get a strong enough spark, so try using a booster battery; if you jump to a car or truck do NOT start that vehicle's engine!

    I've been using a booster with electric start.

  9. #8
    Member ckemps's Avatar
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    Quote Originally Posted by 66Sprint View Post
    What reference are you using to determine compression stroke for a cylinder?

    Has the rotor been pulled and re-installed?

    Please feel free to phone to complete this dialog.......

    I've pulled off the cam head cover to look at both closed valves on the compression stroke.

  10. #9
    Member ckemps's Avatar
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    Quote Originally Posted by Rob Axel View Post
    My question... was it EVER running???
    When?
    Then... what was done to make it not run?
    It ran great for about 10 minutes in June of 18, then a screw fell into the left cylinder and i got the cylinders bored and valves lapped and put everything back together but then it only ran on one cylinder (low compression) but would start (fall of 2018). Now summer of 19 I haven't touched it all winter, and the bike won't even start.

  11. #10
    Super Moderator ancientdad's Avatar
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    You mentioned "The cam and crank have been timed together correctly after rebuilding my cylinder head" and "I've pulled off the cam head cover" - are we talking about a DOHC CB450, or the later SOHC CB450? big difference in ignition and cam timing between the two

    I ask because when we don't have an Introduction, it takes longer for us to fully understand the new member and what bike he has...
    Tom

    CL450 project reboot, street legal this time

    Budget drag bike project

    Ride along at the drag strip



    running points... because I'm too old for mysteries that begin with pushing

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