Howdy again Gang! When I took my TL320 down to Moab last month, with a fresh change of the fork oil to ATF, I found that the seals leaked a great deal. I decided to change them, so I ordered a set of seals for 35mm Betor forks. They came as a set of four separate seals, apparently meant to be stacked on top of each other for a double-lip seal.

Last night, I dismantled the forks and removed the old seals. The old seals were not stacked, they were a single seal on each side, each with a double lip inside. One fork leg was embossed with the words: "Honda F seal, 9125-273-000". So it would seem that someone had the fork legs machined to accept a Honda seal, though I suspect this may have been done at the factory, as the embossed wording is very crisp.

The new seals I bought are far too small, and when stacked, they are too tall as well. So I will need to buy the Honda seal. My problem is this: the part number supplied does not appear to correspond with any Honda part number. I measured the seal, hoping to just order a generic seal in the correct dimensions. I found it to have an ID of 35, OD of 47, and height of 10 or 11mm. Sadly, I can't seem to find anyone selling a seal with those dimensions.

Can anyone shed some light on the correct seal? Is this a common feature on 1982ish TL320s, or is it something that was done by a previous owner?

Hi

The standard seal for Betors is 35-47-7 and normally you can get 2 on top of each other....check to see if there is a spacer ring fitted that the seal sits on, which would reduce the stack height down from 14 to 10mm.

Alternatively, try just using a single seal, its very unlikely to move after being fitted. If you need a double lip seal, drop me a pm as we can get them here in the UK.

Martin

Gday, All Balls (available anywhere) list 4 seals for 35x47 forks -

33-129-44 = 35x47x10.5

33-129-72 = 35x47x10

33-129-83 = 35x47x7.5/10

33-129-67 = 35x47x7/9

The -44's (10.5mm) are fitted to heaps of Euro bikes from the mid 70's like Husky' and Ducati which sounds right to me if they are Betors. Also, make sure there are no mark or nicks in the tubes, anything at all will only cut the seals apart and continue leaking. Basic rule of thumb is if you can feel a mark with your finger nail it is no good.

HTH,

Cheers,

Stork

Thanks Martin and Stork!

There is no spacer in the forks. I've decided to follow Martin's advice, and try riding with a single seal in place. Just finished fitting it all back up, and took a very short ride in the dark. I will report back tomorrow after a proper ride and let you know whether the seals stay in place. My fork tubes are in very good shape. No nicks of any kind. I'm fortunate to live in a desert, where rust is rare. Rubber dries out quickly, though. The old, leaky seals were not torn, just dulled on the rubbing surfaces. The top lip was very dry and hard. I have no idea how long those seals were in place, since I only acquired the bike recently. I can promise you they saw hard use for a few days last month at Moab, though!

I took the bike out for a good thirty minutes ride, and it does not appear that the single fork seal is moving, or leaking. So far so good.

I've noticed a new problem, though. The front forks seem awfully stiff compared to the way they worked before I replaced the seals. Initially I thought the stiffness was due to a change in fork oil. (I had ATF in the forks before, and switched to 7.5 weight fork oil when I changed the seals.) Now I've drained the fork oil, and switched back to ATF. Sadly, the forks still feel awfully stiff, as if I'm no longer getting full suspension travel. It feels especially harsh when I wheelie and the front end comes back down, or when I hit a hole with the front wheel.

When I push my weight straight down onto the pegs, it feels as if the rear suspension travels a great deal farther and more freely than the front. Before the oil/seal change, the suspension was much more balanced, front and back.

I've got my fork oil level at about 6.5 inches from the top of the tube, with the springs removed.

Any ideas on why it should get stiff after an oil/seal change?

Edited April 14, 200917 yr by qcowboy

Gday, probably not enough oil. 6.5 inches down sounds like a big air space - do you have an actual specification for the bike? ( I assume that this measurement is done without the spring and with the fork fully compressed) ATF is actually around 7 weight anyway so that wont be the issue. A big air space above the oil is like a second spring - the air itself, being compressable, acts like a spring. The most important thing if adding more oil, is that you don't overfill which will cause hydraulic lock when the fork is fully compressed. See if you can find a spec, that will sort this question out.

HTH,

Cheers,

Stork

As Stork955 says, it might just be air pressure. I would slacken off the tops to let any excess pressure out (might have been alot colder when you rebuilt them) Tighten up and try again, before doing anything else.

. . . See if you can find a spec, that will sort this question out.

Ha! Finding a spec for almost anything on this bike is a major trick. (Did they even publish a shop manual for SWMs?)

Even without a spec, Stork sussed out the problem, though. I found the 5.5 to 6.5 inch air space spec out on the internet somewhere, in a discussion about Betor forks on some other old trials bike. Seems last time I changed the oil in the forks, I got the message that the measurement was taken with the forks fully compressed. Somehow, a month later, I forgot that part about compressing the forks. That was my problem: way to much oil. I had filled the forks within 6.5 inches of the tube tops with the forks fully extended. Tonight, I removed most of the oil, compressed the forks fully, and then removed some more, until I had a 5.5 inch cushion of air above the oil. Forks extended again, springs back in, caps on, and I love my nice soft front suspension again.

Thanks (once more) for pulling my fat out of the fire. The collective wisdom here found the answer once again!

Seems I'll be riding in my first trial in Colorado this weekend. The bike is ready, thanks in no small part to all of you!

Edited April 15, 200917 yr by qcowboy

Nice!

Stork

Correct oil volume for Betor forks is 220cc in each leg and use 10W oil.

Cheers

Martin

Thanks for the fork oil volume spec, Martin. Was there ever a workshop manual published for SWM bikes?

when i got my 82 new all it came with were about a dozen typed pages held in a folder...it has the basic specs on the engine,frame and some tuning tips...johnnyb

It would be useful if we could get a copy of those pages scanned, and provide a link to them in a thread here, so that they will show up in a Google search for future SWM owners. I'm willing to provide the server space and host them, if someone has a copy they can scan and email to me.

(I could scan them here, if it is easier for you to photocopy and snail mail them.)

Edited April 18, 200917 yr by qcowboy

Hello qcowboy,

The Hondacode middlepart (273) indicates the Honda CL72 Scrambler US .

You can find 35 mm. seals for the frontfork of the CL72 at www.cmsnl.com (search for partnumber).

The complete code is 91255-273-000 (extra 5 in first number).

A set will cost you 12 euro, that's aprox. 17,60 + mail.

Sorry I noticed your question so late, hope it is still of help.

Kind regards,

Arie Bottinga, the Netherlands

Thanks for the reply, Arie! As you suspected, it is too late for me, but someone else may find the information useful later. As long as we're adding to the archive, I purchased double lip seals that were labeled for a 1970s Harley Sportster, and they fit beautifully. Leak is gone!