Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: royhall on February 12, 2016, 04:44:32 PM
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Is it possible to change the main shaft oil seal (34x9mm) on a 400F without splitting the cases. Its the seal that is a blacking piece with an oil supply right underneath (just in front of the sprocket). My mates bike is weeping oil past this seal. Funny, I was only talking about that same thing 2 days ago, think I will also check that seal on my 350F.
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Do you mean this ?
[attachimg=1]
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I'm sure that seal's got a locating tab sticking out and possibly a flange as well to keep it firmly located. Whereas removing it with a screwdriver is do able, refitting the new one is an unlikely prospect without opening up the crankcases a tadge.
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It has got a tab sticking up but no flange (No 272 in the picture), I suppose how flexible it is will determine if it will go in without splitting/lifting the cases.
[attachimg=1]
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That's the one Bodd. If its the same as the 350F it definitely has a dowel shape tab on it.There's a quite large weep of oil coming out at about the 5 o'clock position, right about where the oil feed is under the seal. Do you know of anybody that has successfully changed that seal without a stripdown, or a way of re-sealing it in situ. Don't mind helping him with a seal change but I don't want to get involved in his stripdown, don't have the time at the moment. Think I will get him to order a new seal then I can have a look at how flexible they are etc. Cheers.
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I don't know if anyone has ever replaced one in situ but if it was me I would give it a try, it looks like the tab isn't too big or too far from the edge so I would put it in at an angle locating the tab first then tap it into place, I would also put a smear of Hylomar on it.
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I'm sure that plug is rubber formed over a metal cup, I remember it was not very flexible when I replaced it during my 400 engine rebuild....it will probably be a job and a half putting a new one in and not deforming it.
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You are right about the metal cup dave400, this is what it looks like on the DS website, I would still be tempted to have a go though.
[attachimg=1]
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Sorry not worth wrecking a gearbox trying to do a half assed job
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How is it going to wreck the gearbox ? It doesn't move, doesn't affect any moving parts and if nothing leaks past it it is doing it's job.
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Replacing the leaking crank seal on my 350F (that I stupidly put in the wrong way round) was a half assed job, but it worked a treat. Surely got to be worth a try at the cost of a seal just as long as were very careful. If it doesn't work the engine was coming out anyway, he cant use the bike as it stands.
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If it's just a blanking plug does the dowel need to be there? Could it be dremel'd off???
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Don't see why not. I would avoid using Hylomar in this instance in favour of 'Sticks like Sh*t' (from Screwfix) because of its superior adhesive qualities. If that plug loosened itself while you were riding it would spoil your day.
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If its in wrong it afdfects the oil flow thats why the peg
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How can it affect the flow ? It's a symmetrical cup.
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The oil flow comes out right under the cup, then there's a slot inwards to lubricate the bearing. Bloody stupid idea if you ask me, that's just going looking for leaks as the oil under the seal is at pressure. I am amazed it works at all to be honest. Probably dictated by production limitations on the line.
The oil is coming out at about the 5 o'clock position, right where the oil drilling is. I personally think his engines coming out, but will give it a go at replacing the seal in situ. Will let you know what happens, but I think we already know which way this is going.
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Not especially proud to admit it, but it can be done, I did it reluctantly in the early eighties after a very hurried rebuild, I realised the seal hadn't seated properly. There was no time to strip the engine down again. I got the old seal out with a self tapper, cut the locating spigot off a new seal and put it in with a smear of welseal. I took it easy for a little while but had no issues, it stayed like that until the next rebuild 5 years or more later.
I'm not recommending it as an acceptable practice today, I worked to different standards then and a lot less money, also the bikes had no great value and spares, when available were very expensive, but it has been done before.
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Nice to know it can be done. He's hoping to get a season out of it whilst saving some cash for a proper rebuild. So going to have a go as soon as Silvers can deliver the out of stock seal. Not sure why I ordered genuine Honda when I'm likely to be cutting it up anyway?
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Mate brought his 400/4 round today to have a go at the blanking seal. Got the chain and sprocket off and gave it a good clean around the insides of the transmission area. Sure enough there's a good flow of oil coming from the seal.
The seal looked like it wasn't seated properly as it was close to level with the casting at the top and about 2mm proud at the bottom.
So as it was coming out anyway, thought I would try driving it in until it was level. So using a socket extension and a mallet, gave it some healthy whack's until the seal was level all round.
Ran the engine again and guess what, no leaks.
Cant be that easy, so we left it in the drive running whilst we had a brew and its bone dry. Job done, and one owner over the moon.
Not sure why that happened as the seal was very tight in the casting, must have been like that from new. Then 41 years and 87,000 miles later decides now is the right time to leak.
Not understanding that one, but hey ho its fixed.
Thanks for all the advice and help yet again.
Cheers.
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Don't you just love it when a job you've been thinking about, and sometimes dreading for weeks, turns out to be so much easier than you'd ever dare hope. ;D ;D ;D
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+1
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Ha ha, been following this thread and wishing I could have added some ideas, so it's great to see the issue resolved to your satisfaction. Most enlightening!
Cheers, D.