Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: onethumb on April 23, 2017, 04:22:51 PM
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Right my new OE head gasket has arrived so I'll be fitting it sometime this week ( got to get some oil seal metal tubes). Due to the last one being slightly out I want to cover all bases as it's costing me more than I can really afford now.
I've spoke to several different people and want to know what people here think about using copper slip or blue hyolmar or nothing. Ideas ?
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DRY, and totally clean mating faces, OE head gaskets have a sealant sandwiched inside, which squeezes out as the head is torqued, making it an excellent seal.
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I've never used sealer whatsoever anywhere with OE gaskets on Honda motorcycle engines.
Make sure mating surfaces are spotlessly clean and dry and also oil free and your good to go.
Have fun!
Skoti.
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Just built mine back up today didn't use anything on it also didn't use any sealer on rubber pucks .as recommended by a few people
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Yozzer did you put the 4 knock pins back in with the doughnut seals. Glad it's back together. Nice one.
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Yes I did
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Glad I ordered a replacement now.
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No sealant used or needed on mine, but I did put a touch around the rubber pucks for peace of mind, and because Mark Paris said so, it was leaking from there before it came apart. All dry now.
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I've never used any sealant on a 750 engine but I've always used genuine gaskets and made sure that the mating surfaces were super clean.
Cheers
Dennis
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Thanks.
I'm thinking weather or not to do the piston part while I've got it stripped. It was OK and dry before so thought it would be ok but I've read that people are doing this at the same time as the head because of movement. Any thoughts?
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In business we would never do just a head gasket always base as well to guarantee good sealing, when you have to remove the engine to do anything and the cost of the head gasket as well it was a no brainer to us
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Have seen people using some bond to glue the gasket, why I don't know as this can squeeze into the engine and cause blockages. As others have stated, clean and gasket only needed.
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Thanks. Info always appreciated.
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The using of extra sealant comes from 'Hondaman' on the sohc.net site. It covers the earlier heads/barrels that didn't use the extra dowels/seals. It recommends thicker o rings and sealant in certain area's. I haven't got the .net forum links but kept an extract for future reference - see below.
Extract from sohc.net Hondaman post
'The OEM ones were Buna N (durometer 65-75). Those are real common. Make sure the size is 2.5 x 12mm, not the undersized ones found in some gasket kits lately. I just bought some 2.5x12 in both Buna and Viton, if you can't find any there.'
Not giving an opinion on the need for sealant but just quoting where the use of sealant may have come from - although I used the larger o ring as above on my K2 and its leak/mist free
Phil
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according the sohc specialist that built /restored my bike says using any kind of sealant is a definite No !!
One guy who took no notice of Steves advice insisted it was used on his rebuild & learned the hard way when the top end seized & he needed a new Cam, apparently a micro amount of sealant found its way & blocked the oil feed to the top end.
Obviously a new gasket is needed when rebuilding [no sealant] & the oversized O-Rings is the only way to go.
PS... I know I have got this story correct
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Ive just rebuilt my top end and didnt use any sealant on the head gasket. I torqued it down as stated in the book and it seems fine.
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Thanks. Loving the information.
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I have rebuilt dozens of engines and never used any sealant on japanese motors except for the odd rocker cover where some models have no gasket and of course the mating crank case faces where I use blue Hylomar. I have never had an issues with leaks on any. I do grease paper gaskets, I know there has been loads of discussion on this, but I find it makes them more pliable and less likely to be damaged and also keeps them in place when fitting. I don't see the point of using sealant on rubber gaskets at all and can't understand why you would do this..
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Hi neilg, I'm just asking the question as there are loads of different views and methods out there. I did not use anything the first time and had no intention of the second time but after searching for answers I came across a load of people using copper slip and sealant with good reviews, so I asked here on this forum as it's been the bible of information for a first time builder like me. Thanks for your 2 cents.
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I'm going to do the lot. Any tips when honing the cylinders? (https://uploads.tapatalk-cdn.com/20170428/bc4b38ff14d6d7c22b210c909dffbb67.jpg)(https://uploads.tapatalk-cdn.com/20170428/9c5903c8d9b48dfb1a73549c1dab9a8b.jpg)(https://uploads.tapatalk-cdn.com/20170428/5c86dc3e1a05144105ed5a3c5088a85d.jpg)
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When you say honing the cylinders are you using an actual honing tool or a glaze buster type. If it's a glaze buster be very careful as to how you use it remember these are quite close tolerances that are used. Also keeping the thing straight can cause issues. I know they are supposed to self centre but as I say be careful, use a slow speed on the drill and work it up and down the bore to get the cross hatch. If you have an old set of barrels try a practice first on them.
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Hi neilg, yep it's the deglaze type. Good idea on the barrels. I haven't got any knocking about but if someone wants me to practice on theirs I'm more than happy to give it a go. Thanks dude.
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Just to explain my thoughts, I tried one on a Kawasaki Z250 I was building. Although I had it set on the smallest bore setting it was still tight so the springs were loaded. As I pulled the trigger the whole lot was sent spinning in my panic I pulled the tool out and of course my finger was still on the trigger so it went faster and exploded into pieces when it emerged from the bore and sprung open as it spun, (I'm actually laughing as I type and remember this). I've never tried it again and the last time I deglazed bores was on an old Bonneville, (a real one not the latest pretend model). I did that by hand and with fine emery cloth though they are a bit more solid and not as precise as Hondas. I have considered a second attempt but if I did I would have some one hold the block on its side or clamp it in a vice this time. Remember the stones should be allowed to emerge from the bottom partly and not stop at the bottom as it would if you had it stood on it's base. And use plenty of oil to lubricate things. I think the issue is that these tools are really made for larger bores such as cars and not bikes, as I say even set on its smallest setting by the time it was squeezed into the small bike size bore there was quite a bit of tension on the springs.
Love to hear other peoples experiences wit these.
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Just to deglaze is easier with a flap wheel