After a seizure a couple of years ago, I’ve rebuild my CB72 engine during the winter with new sleeves and pistons. In the spring, I mounted the engine in the frame. To be sure that my partly new engine gets the needed oil, I cranked the engine on the starter motor without the spark plugs.
Well, the oil was flowing as I discovered. Unfortunately, the oil was flowing out of the engine in between the head and the cylinder at the location of the oil passages and the oil seals. And it was really flowing, not dripping. Would it be possible that the seals were damaged during assembly? I was really disappointed, so I stored the bike for the rest of the year, until last week. I took out the engine again and pulled the head to inspect what was going on. At first I did not discover anything. The seals were still ok, and I used bondage to be extra secure. The head gasket was not damaged. What was going on??? I reassembled the head and then I discovered LIGHT! You can see light between the head and the cylinder!!!! On both sides, but not on the middle… See the picture….
My cylinder was flattened, so that should be ok. I inspected the head, and that one was also ok. I used a steel ruler to check the cylinder and the head, both ok. Than I’ve fitted the head without the gasket and found out that the light is gone!!! So the head and the cylinder are flat – what’s left??? The gasket! I used the same steel ruler to check the head gasket and found out that the surface of the paper and the metal rings are not equal. Of course, if you tighten the head, the gasket should compress and seal the gasket to the head and the gasket to the cylinder. But for some reason, it just does not do it, resulting in oil leakage between the cylinder / head and the gasket. It’s only a hair thick, but it’s enough to let the oil pass.
I bought the bad head gasket some time ago on eBay from somebody. Be warned, don’t buy a head gasket with the name Anderson – Kittelson. I am convinced that my fresh ordered OEM part will be more reliable.
Rob - 1965 CB72
Bad Head gasket [fyi]Bad Head gasket [fyi]
head gasketstrikefl, I have the same problem but not as extreme leakage as your's just a few drops from center of head and cylinder. I think my gasket was D&K. I'm going to run it for now and see what happens. I used another head from a newer bike that had an H between the carbs and the original head had an M, that might have something to do with it. I'm going to get the original one redone and swap it out so I'll have factory mating surfaces, but will get oem gasket.
chico(steve)
66 CB77 ride safe
strikef1:
It may not be the head gasket. Assuming that the block and head are square, I'd veture that the "O" rings that seal the oil passages between the block and head, are damaged. I believe the purpose of the head gasket is to seal the combustion chamber and provide a reasonable seal for cam chain tower; there's no way they will seal the oil passages. If the head was warped or the block uneven, for example, a cylinder liner slighty out of whack, the head gasket would "blow" the first time there was a load on the motor.
Rob,
Before you suggest that product are inferior, be certain. I too, used this head gasket in the past, and from my opinion there's nothing wrong with them. Of course it could be that you have an inferior example from an otherwise good head gasket. But be sure about it and check this list : Did you use the correct O-rings ? Are the sleeves pressed deep enough ? How flat are the cylinder and head ? Are you sure you used the right knock pins (11*16) ? Did the head and cylinder touch everywhere without head gasket ? Did you re-cut the treads before installing the bolds ? (if the threads are not that fresh any more) Did you clean the treads of the studs and oiled them with a 80/20 molybdenum/oil mixture ? (or 50/50 copper grease / oil mixture) Did you tighten the bolds on the specified torque ?, and did you follow the specific order to torque the bolds ? Is your torque wrench up to date ? If the head was torqued for a year and it didn't seal, you have to check the head again on flatness. It should be flat within at least 0.1 of a mm, but 0.03 mm is better. jensen assembly of Japanese motorcycles requires great peace of mind (Pirsig)
head gasketThanks for the replies.
For the checklist: Did you use the correct O-rings ? yes, I did. To be sure, I've ordered new ones, as these came with the kit. Are the sleeves pressed deep enough ? yes, they are flat with the surface. How flat are the cylinder and head ? Checked with a steel ruler, they are flat. The cylinder was flattend and if you lay the head on the cylinder, it touches everywhere (no more light at the light spot). See picture. Are you sure you used the right knock pins (11*16)? Yes, the originals. Did the head and cylinder touch everywhere without head gasket ? Yes it does. Did you re-cut the treads before installing the bolds ? (if the threads are not that fresh any more) They are fresh and ok. Did you clean the treads of the studs and oiled them with a 80/20 molybdenum/oil mixture ? (or 50/50 copper grease / oil mixture) Yes, I did. Did you tighten the bolds on the specified torque ? Yes, I did. , and did you follow the specific order to torque the bolds? Yes I did. Is your torque wrench up to date ? I used a second one, just to be sure I do agree with Carl1951 that the seals should seal the oil passage, but if the head gasket does not allow that all the sufaces touch, there will still be a gap between the cylinder / head / seals. The original head gasket and seals are on it's way. I'll let you know the progress.
Hi,
Thanks, the only conclusion is that in your typical case the head gasket isn't good. Like I stated in my previous reaction, I did not had any trouble with this head gasket. For other reasons than above I use a oem honda head gasket. Jensen assembly of Japanese motorcycles requires great peace of mind (Pirsig)
strikef1: I looked at my shop manual to see if there was anything I was missing - no help - also, went into my garage and held a light to my '66 CB77; I could see the gasket neatly sandwiched between the head and block; no light seeped through.
Hope a new gasket solves the problem (the one in your recent photo looks good). If it doesn't and the "O" rings are the correct size, then the head and/or block are not square and need to be resurfaced. One or the other, or both may be warped or contain some other inperfection, albeit too little for you to detect with a steel ruler A couple more questions: Did you check engine compression? Did you torque the head down in the second photo (with no gasket) or was it merely resting on the block? Regardless, let us know the outcome.
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