Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: Graeme77 on November 07, 2015, 05:14:37 PM
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As title.
valve seals seem ok, all dry except number 4 which had lots of oil in the bore. So I know why its smoking on start up but dont know why there is oil in the bore.
The oil seems to be coming from around the stud and leaking past the head gasket. Its number 13 stud in the tightening order. It doesnt have an o ring so im guessing there shouldnt be oil here to start with? With the head off its still full of oil around that stud so is it just going to be getting past the nut and washer? Can oil come up around this stud? Can it drain away from this stud?
I can see no obvious problems with any seating surface and all torques were good.
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One other thing, the 8 studs that hold the cam towers, should they all be studs? 2 of mine are bolts, and they have stripped the thread in the head. Ill helicoil it so not too big a deal but just wondered.
Oh, and while im at it, should the 6 10mm head bolts be tight? Mine werent. Its been apart before obviously but not by me. I have a photocopy of the factory manual but its a but vague.
Thanks.
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Only 4 should be studs on cam towers,. These need to be thread sealed as oil will leak past them because the holes go to the outside world!
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What 750 engine would be a great clue as the K has many differences and the F has a couple of differences. Any pictures ?
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Sorry, 750f1 1976.
I can take pics of anything you need, ill take a few general onesbin a bit.
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Pics hopefully.
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One at a time it seems
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:)
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:)
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:)
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Ive wiped most of the oil away but you can see it around the stud. Number 4 is suspiciously clean. There wasboil from thebstud hole to the bore on both sides of the gasket and oil in the bore.
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One other thing, the 8 studs that hold the cam towers, should they all be studs?
I've found with my bikes that the Parts Lists are really helpful for working out what parts you should have.
There looks to be one for the 750 F1 in Ashimoto's Dropbox: http://www.sohc.co.uk/index.php/topic,8884.0.html
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Good point, I have a genuine parts book somewhere.
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Between 1&2 and 3&4 there should be 4 dowels and sleeves, those look like O rings on yours, and has already been said there should only be 4 studs for the cam towers.
(http://i192.photobucket.com/albums/z244/DennisMcc/Engine/Rebuild-15.jpg)
(http://i192.photobucket.com/albums/z244/DennisMcc/Engine/Rebuild-16.jpg)
This should show it better
(http://i192.photobucket.com/albums/z244/DennisMcc/CB750F1/BARRELS%20F1_zpsgrmmmopi.jpg)
Cheers
Dennis
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I guess the cam tower stud thing doesnt really matter, as long as it all bolts down right.
just had a look and I have all the hollow pins and right seals forbthe studs, just dont know why this end stud is full of oil.
I guess it must be coming down from the nut and washer. Head gasket obviously isnt stopping it getting into the bore.
Should the head washers and nuts be sealed?
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The cam tower stud holes, some of them go through to open air and will leak out and give you an external leak between fins if the threads are not sealed with a good sealer
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I think one has been seeping a bit already so ill remove them all and seal the threads. I used to get a tiny trace of oil between the top two fins on the head infront of number 1 spark plug.
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Cylinders are off and its all clear now. Bores are great, rings are spot on. I know it was rebuilt about 1000 miles ago but that was 15 years ago. Ill put it back together with new gaskets and im sure it will be fine.
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Not an expert but it sounds like a gasket then, the only had nuts and washes that I know of that are sealed are on the F2 but that is a different story
Cheers
Dennis