Gearbox blanking seal.

[royhall]

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.

[PDAY]

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.

[royhall]

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?

[royhall]

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.

[hairygit]

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. 

[mike the bike]

+1

[Drew400]

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.