CB750 valve seals made of Bakelite

Discussion in 'Old's Cool' started by Grinnin, Mar 18, 2013.

  1. Grinnin

    Grinnin Forever N00b

    Joined:
    Dec 10, 2005
    Oddometer:
    2,981
    Location:
    Maine
    I chipped the valve seals off my '75 CB750 yesterday. They seem to be made of Bakelite. These seals are half the reason I opened the engine, but it didn't burn much oil at all.

    Now I wonder about the other seals -- alternator, ignition, kickstart, and countershaft. They wouldn't be subject to the high heat of the head, but I still wonder. The engine doesn't leak.

    I may just split the case and replace them all. I hadn't intended to do that since the engine has shown no problems; this started as a preventive teardown. The cam-chain guide and tensioner show tiny chips missing; another indicator that I need to split the case and replace all the soft parts.
    #1
  2. noman

    noman Been here awhile

    Joined:
    Jun 4, 2007
    Oddometer:
    954
    just now finishing up a full refresh on a cb350f, and starting to dig into the engine to replace gaskets, seals and o-rings. did the clutch cover last night, and what a bear to get the old gasket material off! heat, careful scraping, fine sandpaper. took an hour+ just for that, then another hour to spruce up the cover itself.

    repeating on the alternator tonight.

    i'll be going as deep as the cylinder base gasket. am not sure what can be gained by splitting the cases, and riding season is nigh up here. if nothings leaking well ...................

    good luck in any case
    #2
  3. lrutt

    lrutt SILENCE.....i kill you

    Joined:
    Jul 25, 2005
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    Location:
    Deltona, FL
    I would imagine if you spent that many years in that hot and hostile of an environment with oil covering you all the time, you'd be a little crispy too :)

    But if the other seals aren't leaking, I wouldn't worry about it. Unless you plan to split the cases and replace the primary chain, the of course do them all.
    #3
  4. Grinnin

    Grinnin Forever N00b

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    Dec 10, 2005
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    2,981
    Location:
    Maine
    I got the box of spares out of the shed today. I knew there was an extra battery box and two valve covers (in addition to a spare engine and 8 spare carbs).

    What do I see? Two (2) complete sets of crankcase oil seals still in shrink wrap.

    First world problems.
    #4