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Old 03-18-2013, 05:57 AM   #1
Grinnin OP
Forever N00b
Joined: Dec 2005
Location: Maine
Oddometer: 2,711
CB750 valve seals made of Bakelite

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.
Motorcycles are magical.

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Old 03-18-2013, 10:12 AM   #2
Studly Adventurer
Joined: Jun 2007
Oddometer: 867
fossilized gaskets - grrrrr

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
1976 r75/6 -- mine since 1980, thx lloyd!
1985 vf500f -- v4, 6 spd, 16v, triple discs, water cooled
1997 900ss -- full sp spec
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Old 03-18-2013, 10:56 AM   #3
SILENCE.....i kill you
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Joined: Jul 2005
Location: Deltona, FL
Oddometer: 1,316
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.
2006 HD 1200C, 2006 Tri Scrambler, 2001 Duc M900, 2001 Hon XR650L, 1994 HD Heritage, 1989 Hon Hawk GT, 1978 Hon CB750K / sidecar, 1977 Guzzi 850 LeMans, 1976 Hon CB750K, 1965 Hon 305 Dream, 1973 Nort 850 Commando, 1971 Tri Trophy 650, 1970 Hon Trail 90, 1970 Tri Tiger 650, 1973 Hon Z50, 1984 Yam Virago 1000, 1981 Hon Passport 70, 1970 Suz T250, 1971 Yam RT1 360
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Old 03-21-2013, 09:19 AM   #4
Grinnin OP
Forever N00b
Joined: Dec 2005
Location: Maine
Oddometer: 2,711
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.
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