1978 CB400 - cam chain adjustment - engine running or not - which way is best
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  1. #1
    Member lraklrak's Avatar
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    Jun 2019

    1978 CB400 - cam chain adjustment - engine running or not - which way is best

    I am doing a routine tuning and adjusting on my newly purchased bike.
    It is a 1978 Honda Hawk II Cb400 with 9,000 and some miles.
    I already rebulit the carb, changed oil and filter, changed spark plugs, and replaced the air filter.
    Next is a valve adjustment.
    But before I do that I heard that the cam should be adjusted first.
    Is this the case?
    My next question is can the cam be adjusted without the bike running?
    My manual states to start it - let run at around 1200 rpm - loosen the nut and let it adjust itself.
    Doing it manually I read you stick a long screwdriver down and press on the guide or something until it stops.
    Doesn't sound like something you want to mess up.
    I have the carb off and was going to do the valve adjustment and cam adjustment before replacing it.
    Or would it just be better to replace the carb and start it then let the cam do it's self adjusting thing?
    Does this always work well?
    Let me know which way is actually better.
    Thanks again.
    Last edited by lraklrak; 07-21-2019 at 12:39 PM.

  2. #2
    Super Moderator J-T's Avatar
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    Jun 2009
    Tea, South Dakota
    "The book" gives you the best advice. Doesn't matter whether you adjust the valves before or after adjusting the cam chain.

    Don't forget to also adjust your balancer dhain.
    81 CM400T

  3. #3
    Member lraklrak's Avatar
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    Jun 2019
    Thanks for the advice.

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  5. #4
    Senior Member Bill H's Avatar
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    Aug 2015
    Waverly Ohio USA
    You might do the adjustment with the motor running. I had to replace the slide when a new to him owner pushed down to tight on the adjustment and wore the coating off the slide. Just a thought.


  6. #5
    Super Moderator longdistancerider's Avatar
    Join Date
    Oct 2011
    Vancouver Washington (text 408-239-9580)
    Pushing the adjuster down is a last ditch thing and is easy to mess up and ruin the tensioner. On the 400's the case has to be split to replace it. You can see it in this photo with the string
    1978 CB400 - cam chain adjustment - engine running or not - which way is best-201_4540.jpg
    Jim O'Brien
    1979 CM400T "road bike" modified for travelling
    1978 CB400T1 restored
    1972 CL350 nuts and bolts restore in progress

    https://www.hondatwins.net/forums/22...d-attempt.html and https://www.hondatwins.net/forums/1-...r-attempt.html
    Road Trip https://www.hondatwins.net/forums/11...here-i-go.html or "where's Jim now?"
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  7. #6
    Member lraklrak's Avatar
    Join Date
    Jun 2019
    Yea from the looks of it I will do it with the engine running.
    Just rebuilt the carburetor and mounted it (had fun with that).
    Started the engine and now no hesitation when applying the throttle.
    Next is can chain and then valves.
    After that I hit the road.

  8. #7
    Senior Member drydreamer's Avatar
    Join Date
    Aug 2015
    You have the oe manual?

    you know of cmsnl for the exploded views which can only help.

    Don't forget the balance chain adjustment.

    8k miles so just ran in, 25k + miles of life left in the engine, usually, riding and maintenance dependent.

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