-71 450CB change gasket behind breaker points
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  1. #1
    TRS
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    -71 450CB change gasket behind breaker points

    Gasket behind left front cam base (behind points plate) is weeping in my bike.
    Tried to search on the site but did not manage to find a complete guide, so if someone more experienced could chime in it would be appreciated.
    In my thoughts it goes as this.
    -Off with points cover, generator cover and both valve covers.
    -Engine in left cylinder compression LT mark + 90 degrees.
    -Remove chain tensioner.
    -Off with points plate, centrifugal adjuster and breaker cam.
    -Off with left exhaust cam follower shaft nut.
    -Now i should be able to carefully remove the base without destroying anything?
    -Change the axial seal behind centrifugal adjuster while there.
    -Clean, everything left front back in reverse order.
    -Back with cam chain tensioner and let the spring do the adjustment.
    -Check valse timing is correct.
    -Check/adjust valve clearance, not sure if i would go with manual 0.003 or 0.005mm, see different opinions on this?
    -Back with points, adjust points gap and timing.
    -Covers back.
    -Check oil and hope for the best!

    ///TRS

  2. #2
    Senior Member chaindrivecharlie's Avatar
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    66Sprint, Ancientdad, they know all the tricks for that bike, they will give you a correct answer.

    Sent from my SM-N920R4 using Tapatalk
    Charlie

    1972 CL 175 K6
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  3. #3
    Sensei 66Sprint's Avatar
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    Quote Originally Posted by TRS View Post
    Gasket behind left front cam base (behind points plate) is weeping in my bike.
    Tried to search on the site but did not manage to find a complete guide, so if someone more experienced could chime in it would be appreciated.
    In my thoughts it goes as this.
    -Off with points cover, generator cover and both valve covers.
    -Engine in left cylinder compression LT mark + 90 degrees NO........
    .... You need to find the clearance point for EACH exhaust valve and adjust each to maximum clearance....

    When BOTH are as "loose" as possible, THEN you will have minimal pressure on the exhaust cam.....
    Remove nut from eccentric adjuster shaft on points-base side (or side which will be removed)

    Remove points plate, Bolt and special washer from end of camshaft, and advance unit......
    Slowly rotate crankshaft CCW until ALL three alignment index marks align appropriately.....

    Now remove cam-chain tensioner.......
    -Now i should be able to carefully remove the base without destroying anything?.....
    Yes.....
    But hold eccentric adjuster in with slender screwdriver while pulling base....
    -Change the axial seal behind centrifugal adjuster while there.
    -Clean, everything left front back in reverse order.
    Verify all 3 index marks still align........
    -Back with cam chain tensioner and let the spring do the adjustment.
    -Check valse timing is correct.
    -Check/adjust valve clearance, not sure if i would go with manual 0.003 or 0.005mm, (These are WRONG!) see different opinions on this ?
    ACTUAL spec. is .0012", we recommend you set to 0.002"...... (NOTE INCH measurement, NOT metric)

    -Back with points, adjust points gap and timing.
    -Covers back.
    -Check oil and hope for the best!

    ///TRS
    See above......
    Once the points base is re-installed, just follow the FSM as if you were completing an engine rebuild.......
    Last edited by 66Sprint; 06-06-2019 at 01:57 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

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  5. #4
    TRS
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    Thanks a lot. My mistake on the clearances, one 0 too much, 0.002" converts of course to just over 0.05mm, not 0.005mm!
    ///TRS

  6. #5
    Senior Member ancientdad's Avatar
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    And one more thought... the cam chain tensioner spring is NOT strong enough to do the work for you all by itself - you should, while the valve covers are off, turn the engine to a point where an exhaust valve is being opened to put tension on the exhaust cam, which tightens the front of the chain (direction of rotation) and then let the tensioner adjust the back of the chain while holding the crankshaft in that position, then before letting go, re-tighten the lock bolt on the tensioner to keep it there. To check the success of the effort, turn the engine to point where no valves are being opened by one cam and then the other and check the chain tension with your finger
    Tom

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

  7. #6
    TRS
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    So good to get help from people who have knows their stuff.
    I am quite good in wrenching, done it since almost 50 years ago when i bought my first car at age 11, 1952 years beetle.
    Then when it comes to knowledge of a specific car, bike or whatever, the chats are a goldmine with helpful people who have already been there!

    ///TRS

  8. #7
    Senior Member JamesPal's Avatar
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    One more thing, be sure to check the cam end clearance. Most likely the new gaskets will be different thickness and that will change the end gap.
    Jim Palmer
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    https://www.hondatwins.net/forums/1-...s-cb450k5.html
    What I learned from Restoring a CB450 K5
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  9. #8
    Senior Member Lefty's Avatar
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    One more thing, check the cam bearing and journal against factory specs to make sure you're not doing it all for naught.

  10. #9
    TRS
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    Thanks will do. Waiting for gaskets/seals from David Silver. Ordered also carburator repair kits. Left one is sometimes weeping so probably float needle is not always sealing.

  11. #10
    Senior Member ancientdad's Avatar
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    That brings up another thought - be sure to ALWAYS turn off the fuel when the bike is not running, the stock carbs have the tendency to "weep" past the float needles and into the intake ports, and through an open intake valve can leak fuel into the bottom end past the rings and slowly dilute the oil, causing engine damage if not discovered
    Tom

    Ride along at the drag strip - https://www.youtube.com/watch?v=20jFPazXlvU



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

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