Gearbox blanking seal.

[royhall]

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.

[Bodd]

Do you mean this ?

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[mike the bike]

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.

[Bodd]

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.

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[royhall]

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.

[Bodd]

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.

[dave400]

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.

[Bodd]

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.

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[Bryanj]

Sorry not worth wrecking a gearbox trying to do a half assed job

[Bodd]

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.

[royhall]

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.

[Bullit]

If it's just a blanking plug does the dowel need to be there? Could it be dremel'd off???

[mike the bike]

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.

[Bryanj]

If its in wrong it afdfects the oil flow thats why the peg

[Bodd]

How can it affect the flow ? It's a symmetrical cup.