Topic: Fork Oil Seals

[Darren Jakal]

Hey guys (I wrongly posted this in the project shop forum if someone can remove that it would be great)

I’m going over the front end and I am planning to rebuild the forks (take apart, clean, inspect and replace necessary parts) and I’m looking for some more guidance, this time about fork oil seals.

If you watch this video titled “Vintage Honda Motorcycle Fork Seal Replacement”:

you will see (at around the 6:00 minute mark) the author using water to hydraulically push the oil seal out of the lower fork leg (not suggesting this as a way of doing it, but  it did work so …)

Now I haven’t started taking the forks apart yet, and right now the seals show no sign of leaking, so my question is:

If you could lift a building with the existing fork oil seals would you just call it good, or would you replace them anyway because they are old (or for some other good reason that I don’t know)?

Hey, thanks again for all your help!

Cheers, Darren

[ekpent]

 If I was already in there and the fork seals were original I would replace them with some new OEM.

[chewbacca5000]

It is super easy to do.  Just loosen the fork nut before removing the forks, remove the snap ring with snap ring plyers.  Empty out old oil into a pale.  Next remove the fork tubes by hand.  Use flat scewdriver to remove seals from fork lower.  Use 2" pvc pipe to drive in new seals reasemble. 

Worst part is the nasty old oil.  It stinks.

[John Eberly]

Sometimes it is not so easy to get the old seals out.

I have used the hydraulic method to pop them out - overfill the lowers with oil or solvent and put the tubes in, brace one end and use a hydraulic jack to compress the tube until the seal pops out.

Last time I did this with the fork tube under the edge of my deck and a flagstone paver under the jack.

[BomberMann650]

That's a lot of unnecessary stress on your fork!!!!
Just use Localized heat until the seals can be removed easily by hand.
Do your clean up/polishing etc.  When ready, use the heat again, grease the seal, and use a big socket to push it in.

[Darren Jakal]

Hey thanks for the replies!

So the original question was "is it always best to replace these seals regardless?" Why?

As I mentioned the guy was able to almost jack up the building with the seals that were in the forks.

Anyway, I have them apart, but haven't pulled the seals yet. I generally wait until I have replacements before I remove anything. That way I can compare parts and not have to rely on my memory.

Cheers, dj

[martin99]

Must have been lucky all these years. Never had a problem removing fork seals. Flat blade screwdriver, packing to protect the tops, penetrating oil and patience has always done the job for me. Of course it's Sod's Law that the next set I do will be trouble, so I'm keeping this hydraulic method in the ol' memory bank...

To answer the original question - yes, replace them. New rubber is better insurance than years-old stiff rubber.

[przjohn]

Is that video for real? Is the Tequila part suppose to be funny? Ya gotta love when incompetent narcissistic computer geeks or engineers start posting stuff on You Tube about motorcycle stuff they have absolutely no clue about. As soon as you see the neatly organized shed with the table saw hanging on the door and no grease or dirt anywhere you know you're in for some experienced commentary. Hey, if I wanted to know how to never have sex again I would ask this guy. As far as anything mechanical, I'd look elsewhere.  HTF did he get his hands on a CB400F anyway? Never know, somebody here might be able to trade him for a Bobba Fett action figure and a date with a real girl for that baby four.  If you really want to experience these Clowns at their best, check out some You Tubes on replacing Vacuum Cleaner Bags, talk about, "Hey Fella, Get A Life"

Now, to the simple task at hand, heat is your friend. The Geeked out Engineer/IT Guy in the video had finally figured it out but needed to over complicate the simple problem on the other leg as these types often do. Buy a cheap $20 Propane Torch at Home Depot and heat the outside of the leg around the seal, don't heat the inside. When you see a little smoke or anything off the seal use a screwdriver to easily pry the seal out. Always replace the seals when the legs come apart.

I would love to see how these IT Cube Dwelling Geeks would live in their own world. Wouldn't it be cool if while they were away from home at work they came back to find the light switches on the floor, stove in the living room, and the toilet in the kitchen because they had gotten an automatic update?

[BomberMann650]

Not sure about przjohn's torch recommendation.  Open flame and oil residue could be a problem.  My cheap harbor freight electric heat gun was more than adequate.
Fwiw, there are a couple of pics here of broken fork legs.  Guys that went to pry out their old seals and the aluminum broke instead 
Moral of the story, heat is your friend.

[Darren Jakal]

OK, so the verdict is replace the seals even if they are holding up a building.

cheers, Darren

[Stev-o]

Thread Jack: DJ - is that you in your avatar skiing the powder?

[Darren Jakal]

Hey Stev-o,

Yea that's me last year in the Kootenays.

[Smudgemo]

I just did the ones on my 550 that have probably been in place for decades, and it was easy.  I even pulled the tubes to replace the plastic piston ring and nothing was difficult (although taking off the fender and brake takes time.)

The stuff at the bottom of the fork after draining the oil was somewhere on its way to being grease, so be ready to clean inside the slider mechanically.  Pull the oil locking piece (so it's called in the parts diagram..) to get at the crud below it, and don't forget to put it back in before the new seal or you might be buying another seal.  At least it didn't look like it it was small enough to go past it.

I wish I'd have thought about the heat to help.  I just locked a screwdriver in my vise and pulled downward on the slider to lever the seal out.  Seemed safer and easier than holding the slider and trying to work the screwdriver.  Rags to protect the slider from damage, of course.  I happened to have an almost perfectly sized bit of aluminum tube to tap the new seal in place.  Just drive it in enough to reinstall the retainer.

[Stev-o]

Hey Stev-o,

Yea that's me last year in the Kootenays.

Looks awesome!  Been over a year since I last skied and quite a few since I've seen waist high powder....

[BomberMann650]

Hey Stev-o,

Yea that's me last year in the Kootenays.

Looks awesome!  Been over a year since I last skied and quite a few since I've seen waist high powder....

We should not speak of the winter 2014.  It was a Pitiful season.

[martin99]

OK, so the verdict is replace the seals even if they are holding up a building.

cheers, Darren

You're really not keen to do these are you?

Of course they need to be tight in the slider tops, to stay in position and prevent fork oil from escaping around the outsides. Probably best described as an 'interference fit'. But that bears no relevance to whatever seal they might still provide round the stanchion. In use, they will probably set even tighter as rusty crud and oxidation makes an appearance. It is the inner diameter that increases - and thus provides ever-decreasing sealing - with continuous movement of the forks. Age also has an effect, with the rubber becoming less supple, and the springs in the seals losing their tension.

Just be sure to order OEM or whatever the guys here recommend and you'll be fine.

And has been said, the guy in the video is a knob-end...

[jamesw]

One thing to mention to the thread originator, be sure to install the fork seal the right side up, and not upside down.

The OEM Honda seals for my K5 750 are to be installed with the writing facing up.

[DaveBarbier]

OK, so the verdict is replace the seals even if they are holding up a building.

cheers, Darren

If it were me, I would start removing the forks to replace working seals. But if I had them on my bench already then it's a no brainer.

Edit: Oops! I mean I WOULDN'T start removing the forks just to replace working seals. Crap.

[ekpent]

 Lets talk him into repacking the steering bearings also 

[Stev-o]

Lets talk him into repacking the steering bearings also 

No...let's talk him into replacing perfectly good ball bearings with tapered bearings!

[DaveBarbier]

Edited my post above. I didn't proofread, haha.

[greenjeans]

If the seals are hardened and gouged, for sure get new seals.   But...the last 2 bikes I've done, I replaced the seals.  Both of them appeared like they leaked.  However, when I took the seals out and inspected them, I didn't seal a thing wrong with them at all.   That's when a dirt bike buddy of mine told me about Seal Mate.   Cheap easy and reuseable.
I tried it out on my current build.  The seals definitely were leaking.  Very little oil in the fork - most was all over the forks, and boots.  To my suprise, it appears to work.  I cleaned them up a little, put new oil in them and put about 20 miles on them.  No leaks!   

Here's a video.  I am not affiliated with this company in any way.

[Darren Jakal]

OK, so the verdict is replace the seals even if they are holding up a building.

cheers, Darren

You're really not keen to do these are you?

Of course they need to be tight in the slider tops, to stay in position and prevent fork oil from escaping around the outsides. Probably best described as an 'interference fit'. But that bears no relevance to whatever seal they might still provide round the stanchion. In use, they will probably set even tighter as rusty crud and oxidation makes an appearance. It is the inner diameter that increases - and thus provides ever-decreasing sealing - with continuous movement of the forks. Age also has an effect, with the rubber becoming less supple, and the springs in the seals losing their tension.

Just be sure to order OEM or whatever the guys here recommend and you'll be fine.

And has been said, the guy in the video is a knob-end...

Ha ha, yea it's not that I'm not keen on doing them it's just that I'm keen to not make work for myself unnecessarily.

I drive a 22 year old japanese inter-cooled turbo diesel and I find the old OEM parts are far superior to any new parts I can buy. Seems like old rubber was just better. Maybe they used better stabilizers or something in those days.

Anyway, I have tapered bearings that I will install and as for the powder it's on this year.

Thanks everyone for replies!

Take care, Darren

[Chachi]

I think Hackaweek's vids are really good. He might be a member here?

73 Honda CB750 Cafe Racer Build Episode 7 - Front Fork Assembly

[jamesw]

I think Hackaweek's vids are really good. He might be a member here?

73 Honda CB750 Cafe Racer Build Episode 7 - Front Fork Assembly

He installed them upside down in this video.