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1978 CB 750 F2 - Oil pouring from above head gasket
stoutgoose:
Thanks all. I performed a complete rebuild on the engine, so it was completely stripped, chemically cleaned, the head skimmed and block decked, new guides and seats ground, repainted/powder-coated and reassembled using new seals and gaskets.
I made sure all oilways and journals were cleaned and used a MLS head gasket to assist with eradicating the oil leaks associated with the seal height issues.
The rocker gasket is on correctly and there are no leaks (yet) from the head gasket. The pucks were installed using Hondabond. I ground the four head dowels to compensate for the decking and skim and used a larger base gasket to ensure pison clearances were maintained.
I know for sure that at least one of the copper washers is on the wrong stud because I can see it on the one exposed studs at the front of the head. I also did not use domed nuts on studs 5-8 because the manual I posess omitted this crucial information.
The oil seepage is coming from the areas surrounding suspect studs 5-8, but the thing that confounds me is the amount of oil that came out; as per the description quote in my initial post, the oil dribbled out quickly whilst the engine was running. It's alarming how much oil is leaking down the threads of studs-5-8 and past the (non-sealing) washers.
Thanks for all of your comments.
Trigger:
That is a very confused way to build a engine. Deck a engine that is already a high compression engine is asking for trouble :o
This is a common problem that I come across when building customers engines. If the bolts in the towers are in the wrong place it punches out the bottoms. There are two lengths of bolts on the towers, get them wrong and you have holes were, there was not before.
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stoutgoose:
Thanks that’s a useful tip; I’ll check the bolt lengths when I get the engine out again.
Out of interest, what’s the issue with decking the block and using a thicker base gasket to compensate? What’s the alternative?
(When I say decked, .006" was taken off to smooth the surface and remove some dinks in order to make a perfect surface for a MLS gasket).
Trigger:
You said, deck. That is a skim ;)
Not very easy to skim the barrels on the top as, you would have remove the liners and skim the top with a alloy cutter in the head skimmer then, you would need to replace the liners and use a cast cutter on the liners or do the liners on a milling machine.
Seems to be a lot of expense to fit a MLS gasket when, you could of just fitted a Honda one or Vesrah ;)
stoutgoose:
I used HT Howard in Slough who use equipment that detects the metal type and adjusts the cut accordingly; in this case it accounted for the alloy head and steel liners without the need to remove the liners and the associated work you mention. The cut is excellent.
The original oval fire-ring gasket for the F2 is obsolete from Honda; do Vesrah make the oval type? Anyhow, the cost of the skim was reasonable and with the reduced leak potential promised by the MLS gasket I thought it a good idea, but time will tell.
Thanks for the information.
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