Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: Bitsa (Ralph Wright - RIP) on December 28, 2012, 12:57:19 PM
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Hi Guys,
All your experiences wanted.I have a tiny dribble of oil leaking out between pots 2 and 3.When I rebuilt it I used all genuine gaskets and have never had leaks must be lucky but I have only ever had leaks using pattern ones.I stripped it down again checked all the bolt holes for leaks as I know PO helicoiled 1 cam cap bolt and drilled too far and came out in the cavity above the spark plug which dribbled last time.All seems fine the pucks are dry but the only oil I could see was from the rocker gasket.It was not soaking wet but looked like the same as the head gaskets used to weep.I do have another Honda one but before I fit it what I am asking for is has anybody goo ed it before?I have never had to before but I do not want to do this again.On the pics it is just behind the front 6mm head bolt.On the head the oil settled on the fin level with the exhaust flange screws.
Thanks
Bitsa
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Might seem a silly question but are you sure the gasket was the correct way round as it will fit the wrong way and leave a small hole for oil to leak through
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Bryan.
Cheers for that but on one of the photos it shows the gasket in place what I can not work out is its only wet on the outside not the camshaft side weird.Also what is special about the cam cap bolts that seem to strip their threads easy.Being an Ali head you would think that they would strip first.Can I use ordinary 6mm bolts at the right length as I can not find in cabbage ville Allen bolts long enough, some original are not available now?
Cheers
Bitsa
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For the gaskets on these engines I've always used Blue Hylomar.....I know others don't agree so they'll have to offer their own view.
I just use the smallest amount possible to apply the most sparing film to the gasket itself and let it dry....then clean the metal surfaces with a degreasant before assembly.
My feeling is that the bolts all around the head are torque limited ( i.e. you can't risk just doing them up any tighter for risk of stripping) and even if you could do that then the gaps between the bolts seem big enough that you may even cause local distortion that just achieved higher clamping around the bolt location and not the other areas.
If you want some allen bolts from the uk I could certainly look for some for you and post over...there is a very old fastener supplier I've used for years that I could try for you but would need a spec to check availability...it wouldn't be the quickest process but the offer's there if you want.
Nigel.
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Like Nigel says blue hylomar is the way to go, i done my f2 two years ago and used hylomar on every gasket it is leak free on all gaskets, but you have to go easy with it, use the spray if you can get it, that is what i used
Pete
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I would be checking very carefully for hairline craks in that area or gasket surface damage.
I see no reason that you could not use any decent quality bolt, even studding with a nut
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Hi Guys,
Thanks for all your replies will get out a magnifying glass and have a good look for cracks etc.K2 K6 thanks for your offer.I will visit my favourite breakers in the new year I am sure he will help me out but if not I will come back to you.I have always sealed head gaskets to stop the weeping but hey for the rocker this is a first but I guess there is a first for everything sometime.
Thanks again and have a good new year.
Bitsa
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Bit late now.but I have always used threebond gasket material. I believe it is the closest thing to Hondabond, if not the same. Also, it is a nice silver grey and does not show up in the joints
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Just an update guys
Cleaned all surfaces found two very little gouges if you like on the head surface could only see them with a glass me getting bad eyes rubbed them with real light paper got them out.The new gasket seemed thicker to me and I also sealed it.Have now ran it for about an hour on and off and seems to be dry.I can see oil both sides through the tappet covers and its squirting all over.I have not put the exhausts on yet don't want them getting rusty in all this damp weather forgotten what a four sounds like without exhausts I must have awoken the village up boy noisy or what.Anyway as soon as it warms up a bit will fit pipes and take it for a spin and check again for the leak.
All the best
Bitsa
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Hi Guys
Well yesterday was warm enough for my first ride of the year 12 degrees.Silly grin on face again and no oil leaks as yet thumbs up for sealing the rocker gasket.Thanks for all your tips.Hope the UK warms up for you guys soon.Next outing for me is a 2 day parts jumble in Niort in March loads of bikes,bits,beer and rock bands reminds me of the old days sleep where you drop no hassles.
Cheers
Bitsa
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Know what you mean Bitsa, not been using my F1 over this winter as I have a car space at work, but took her out for her first real blast last weekend, that grin is involuntary isn't it? never had that in a car.
The spares do sounds real cool!
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Waggles
You are right driven some nice motors in my time never had the boy grin.Don't know what causes it but its instant the moment you pull away.Perhaps its due to all the work we put into them to get them back on the road.
Cheers
Bitsa
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Think its loads of things! Theres definitely a 'joy' in getting something working well by the sweat of your brow ( and flipping great wodges of cash ) but also the power is addictive too, then theres scratching round a corner, feeling 19 again ( well in some ways ;D ) doing something you really shouldn't be ( at my age I should know better etc ) and growing old disgracefully.
Then, of course, there is comradeship.
There ain't no cure for biking once its in your blood.
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Waggles,
Spot on mate
Cheers
Bitsa
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Just an update
For over 500 kilometres no sign of oil leak.Guess what started again really made me mad.Sat there and thought what have you not done.All of a sudden came to me the only thing I did not do
was not change the rubber seal around the top breather top.I thought what the hell given up now change it and see.Guess what leak has now stopped I would have not believed if I had not experienced it.I had thought in this compartment it was only oil mist did never consider that on reaching the air outside would I guess change back to oil and dribble down the center and give that type of leak.Be warned we are not too old to learn.
Cheers
Bitsa
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Hi Bitsa good to see you found it.
It funny I've been using the Triumph the last couple of weeks and had exactly the same thing
I noticed oil on my boot looked at the back of the engine to find oil over everything :o So I decided it was the rocker cover gasket so I striped the bike down thinking it was going to an easy fix only to find I had to drop the engine so no biggie remove rad,exhaust and a couple engine mount bolts whats hard about that.So with the luck I have it goes wrong almost instantly I undone a couple of studs with ease the third one ping snapped instantly So a trip to the dealers.I come back seal the rocker cover place the engine back in and ping the engine mount bolt striped it's thread.So two days later back down the dealers come back push the bolt in I can't find a nut to fit ??? anyway I've used it this week no leaks until to day I pulled away it's like a two stroke blue smoke so just pulled it apart again to find the air filter box full of oil so a bit of head scratching I noticed oil drip from the crankcase breather BINGO found it the breather seal split.
Regards Thread hijacker ;D
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As others have suggested, a thin smear of Blue Hylomar is a good idea. I've been using this stuff for over 38 years of engine building & have never had any problems & still use the stuff for many modern engines.