Author Topic: 1972 CB750 head gasket replace - in or out?  (Read 2045 times)

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Offline callbr549

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1972 CB750 head gasket replace - in or out?
« on: July 23, 2010, 04:01:42 PM »
Looks like I have a head gasket leak or a leak around one of the oil seals in that area. I would like to replace them so I can ride to work without oil spots all over the legs of my khakis. I'm just starting to think about planning for this project, which would be far and away the most extensive engine work I've ever done. I've looked over some procedures, posts here, etc., but am still not clear on one thing -- can I take the cylinder head off and replace gaskets and seals with the engine in the bike, or do I have to take the whole thing out?

Rob



Offline scunny

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Re: 1972 CB750 head gasket replace - in or out?
« Reply #1 on: July 23, 2010, 04:08:07 PM »
motor out I'm afraid. Hednut was selling frame kits to allow headwork on the bike, http://forums.sohc4.net/index.php?topic=64333.0
« Last Edit: July 23, 2010, 04:17:48 PM by scunny »
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Offline MCRider

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Re: 1972 CB750 head gasket replace - in or out?
« Reply #2 on: July 23, 2010, 04:58:23 PM »
Yup gotta take the engine out. Its cathartic. In my hayday, working in a shop environment, we could get an engine out in 45 minutes, replace the head gasket in 2-3 hours depending on how much cleanup and misc the customer wanted, and back in and running in about 1.25 hours. Those days are long gone.

I remember 3 of us swapping an engine completely in the pits at a drag race in less than 45 minutes. Of course there were a lot of street legal parts missing.

If its your first one, and you are really committed, I'd say out in 3 hours, headgasket in 3 to 5 hours, and back in and running in 3 hours. Assuming you've got all your parts in order, tools etc and nothing major goes wrong. Strip an exhaust flange bolt, or a cam tower bolt, etc.

Strict attention to detail should fix your leak.(s)

If you want to guarantee a no-leak motor, you'll need to take the cylinders off and replace the cylinder studs with heavy duty ones. Add 5 hours assuming you don't break one of the old studs getting it out. About a 50/50 chance.

Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
Youth and Talent are no match for Age and Treachery.