Topic: Fork seal pops out of place. 74 550 [Solved kinda]

[Dimitri13]

I've driven in a new seal several times into a fork with a new tube but the seal keeps popping out.
My other fork with the same seal and same new fork is fine. Fork seals never leaked before the rebuild but I needed to put in new tubes so I had to rebuild them.

Any fix for this other than buying a new lower?

[754]

Shim it or seal it.. , or remove the leg, clean it and build up with paint where needed.
 Myself I might machine it and sleeve, but I don't think it's worn that much. Seeing as it is winter you could get a few members to measure any new seals they got, 2 ways....your may be under..

[seanbarney41]

how is it getting past the lock ring?

[Dimitri13]

I might try shimming it.

It's not getting past the lock ring, but it's unsealed by the time it gets to the lock ring.

[bryanj]

Then the seals are not the right thickness as the lockring should be on top of the seal toght

[Tomshep]

And if the thickness is wrong, then there is no guarantee that the diameter is right either. You have the wrong seal.

[Dimitri13]

Thanks for the advice. After googling some pictures of the fork seals, some I see are tall, like they would fit snug between the bottom sealing surface and the lock ring, others are the same height as mine.

According to CMS the seal from the fiche is 35X48X11. I'll take a look at mine in a bit.

The vendor I bought the seals from no longer have them listed on the site and seem to have been superseded by ones that look much taller.

[robvangulik]

The size is moulded in the seal itself on the topside....

[Dimitri13]

My seals are 35x48x11.

[seanbarney41]

I just did fork seals on a 75 550k about a month ago.  I ordered Honda oem from Partzilla.  They were not the tall ones that come all the way up to the clip.  I did not press them all the way down, just far enough to get the clip back in....this is what I have always done with Honda's, as the tall seals seem to be nla, have not had any problems.

[754]

When I said at the beginning to measure, I meant use a caliper. You have a leak. If you measure a seal with tape or ruler it will be 48 mm they all will. But to work they have to be about 48.1 to fit a 48.0 bore. So what I am saying, either yours are small or the bore has worn.. and you need to find out.... or get another leg. Of course longer ones grip better. Sometimes you have a good fit but there are scratches, so they still leak....harder to fix.  Scratches are only there from idiots removing seals that don't know how to do it. Bore should be bright or shiny, if it's not, seal has maybe been moving around in there..

[PeWe]

CB550 use same seal as CB750?

If it does.....
CB750:
Many seals are thin and weak. Honda published a Bulletine when they changed from 11mm  thick + washer to 13mm that also is much more rigid.
DSS sale rhe latter one. I have extra sets. This model is much tougher to get in place snd remove, heat and tire iron needed when removing it.

That was the model I got here when replacing them 1980 and 1983 when I changed tubes.

 Strange that the weak earlier bad one is the model that all sell today. Leak is not that visible if using gator boots.

Here how I got the knowledge about this and could order good seals, the correct one.

http://forums.sohc4.net/index.php/topic,131619.msg1468995.html#msg1468995

The bulletine is not available in that link, search the name and you'll find it. I have attached it as file in some posts.
http://forums.sohc4.net/index.php/topic,156338.msg1791143.html#msg1791143

[Dimitri13]

754 I get what you're saying. Mic'd it and it was 48.03. Bore mic'd at 48.02. Bit hard to measure but that's the best measurement I could get.

We honed the bored then shimmed it with a thin strap of nickel that my dad had, unsure what it's for but I think plumbing? Nickel and aluminum are very close on the galvanic compatibility scale so very low chance of corrosion. Not a permanent fix but enough that it won't leak. Will either end up replacing the housing when I get to my new house or will finally go for the front end conversion like I wanted.

PeWe, I think the 450, 500/550 and 750 use the same fork seals. If I end up rebuilding my units instead of doing a conversion I'll check in on the correct seals.

Thanks for all the info y'all.