Seca900 fork seals

I'm planning to change my Seca900 front fork seals as soon as weather warms up.

I have tried several times to loosen the frok caps, without success. They seem to be jammed tight. THey are of the recessed tyoe, so I need to use a big allen key:



I started putting some acetone-ATF mix but I didn't make any difference. I tried to use a 12 inch long extension, no go.

The dumb qusetion: do I have to loosen the upper pinch bolt first?

Should I try to use some heat (propane hand torch)? What about hammering the cap gently, using a big hex socket? Heat and hammer in alternance?

Any advice is welcome.

 

Loosen the top clamp pinch bolt.
Don't go hammering or heat or owt else. :roll:

 

Relieve pressure on the upper pinch bolt, and use a long breaker bar on the wrench. An extension on the Allen wrench would only cause the handle to twist laterally and might cause the wrench to "walk" out of the hole.

 

Thank you guys!

I just broke them free with a 2 foot long breaker bar, easy!

Then I decided to drain the forks . I got close to 200 ml of thick, dark grey nasty stuff out of the RHside leg, and pretty much nothing (25 ml or so) out of the LHside leg.

That would explain why I felt a clunk at every bump in the road the only time I rode the bike last summer.

NOw I don't know a lot about fork oil but I doN't thnik this stuff is supposed to be close to black, right?

 

New fork oil should not be black. Old fork oil will be.

 

I haven't been into a fork repair myself. I'd like to change oil seals and every thing else that is usually a part of a fork rebuilt.

Is there anything about '83 Seca900 forks that would require special attention or special tools that other XJs wouldn't?

My forks don't have the anti-dive links anymore (they're blocked off) and I don't feel like they are essential if I put heavier oil and maybe some preload under the caps.

Am I right?

 

PO had owned that bike for 3 years and he told me he had the fork seals changed. I bought it one year ago.

I would think that fork oil takes more than three years to become that dirty.

Sounds like another seller's lie.

 

Has any Seca900 owner here ever tried to lower the front forks a bit to make the bike more tipped forward?

 

The 900's Front Forks have a "Snap-ring Locator" affixed near the top of the tubes. Those Snap-rings act as a stop on the Top-end to position both tubes opposite the Inlets, ... where their openings for the Air Passages for adding Pressure to the Top Tubes align to the married Air Lines from the single Schrader Valve.

Circular Rubber Seals on the Forks above and below the orifices on the Tubes make the system air tight.

 

I tend to think this air circuit looks to me like another useless gizmo, but it may be a rude judgement. I'd like to hear pros and cons.

I'd also want to know what would be my options if I'd decide to put forks from a newer bike...suggestions? I suppose that i'd have to change the whole braking system then, rotors included?

I had a look in my manual, can't even find the inner tubes diameter...is it 38 mm?

 

Actually, I'd like advices from the XJ900 guys here as if it would be a good or bad idea to ignore the air system at the top of the forks in the rebuilt process.

Has any of you experimented the difference in handling with' let's say 14 psi, 7 psi and 0 psi in the air system?

Could there be another way to achieve the same level of handling? preload? heavier fork oil?

I don't like the idea of rebuilding something I wouldn't really need, but if a great majority says that anti-dive and air system are essential, I'll rebuild them while I'm in there.

 

there is not really anything to rebuild, you can replace the O-rings at the top of each folk were the air line balances each folk but thats about it.

 

According to the diagram, there are 2 o-rings at the top of each fork tube and one smaller o-ring at each end of the air hose joining both tubes, meaning a total of six o-rings.

Not a big deal indeed, but the question remains: does the small amoutn of air in the forks make any difference in the shock performance and handling?

 

The additional air spring does indeed effect handling, but whether you need it or not is very dependent on how you ride, and how much load you have on the bike (1 up, or 2 up with gear). I run 20wt fork oil and no additional air on my 750 and that works fine for me solo, and even with a week's worth of gear ( I pack light). 2 up requires some additional air. The air spring is essentially adding more preload, allowing you to adjust the forks the same way that you can adjust preload on the shocks by turning the ramped spring collar.

It is possible, even somewhat likely, that the o-rings you have can be reused if you are careful when you disassemble the forks. They don't come in contact with the oil, or sunlight, or much heat, so will tend to age slowly compared to o-rings in other applicatons.

 

k-moe
Thanks, this is one of the answers I was looking for. When you put heavier oil, did you stick to the amount recommended?


It seems that these o-rings yout talked about are included in the basic rebuilt kits Len carries. I'm in the process of selecting the parts I will order, and advices forn the forum are appreciated.

Now, what about this anti-dive device? Mine is desactivated, should I bother rebuilding it? I don't have the lines betwwen the calipers and anti-dive anymore...

 

The 750 calls for 20 wt oil, but I have occasionally thought about going to 15 wt. That would likely mean that I would want about 5-7 psi in the forks.

I happen to like the anti-dive, though others don't. It works just as Yamaha advertised when set up for the bike's current load.

Mine just needed tearing apart and cleaning to work correctly. Some of the internal parts aren't available, so be careful if you go that route. The 900's anti-dive is somewhat different from the 750, so I can't comment on how easy it is to work on(it looks like the 900 has fewer small parts). The easy way out is to make a blanking plate from aluminum and remove the anti-dive, but what's the fun in that.

 

On mine , the PO or the guy before him remove the lines and put block-off plugs.

 

Looking at my manual, I saw a special tool called a "fork seal driver".

IS this essential or may I use a piece of tubing of the right diameter?

 

Can anyone tell me what is the proper size of nut I should weld at the end of the bar if I build my own damper rod tool for my XJ900RK (1983) forks?

 

I use a length of PVC pipe to drive the fork seals. I'm not sure about the damper rod tool. My guess is 22mm, but it might be 19.

 

I noticed something weird today: my forks upper (inner) tubes look like someone sanded or lightly grinded them in the travel area. I'll try to take some pictures of that, but it may or may not show up. I definitely can see the strokes, longitudinally.

I wonder if it could prevent the new seals from sealing properly???

 

22mm worked for me

 

All right, thanks!

 

Here is what the strokes on my forks look like:



I took some measurements on the buffed section and on the untouched one with an digital caliper. Buffed section showed minimum meausrements of 36.52 or 35.53 mm, depending on the spot. Upper part of the fork showed consistently 36.54 mm in diameter.

I know this is not a big difference but i wouldn't be surprised this is the main reason why the forks leak.

What do you think? Should I buy replacement inner tubes?

 

You could polish them away, but you'd be below 36.52 when you're finished.

Can you feel those marks with your fingernail ??

 

The bottom section has been partially polished by the friction of the oil seal and the dust seal, I guess, but my thumb nail produces a distinctive sound when I lightly scratch the upper part of the buffed area.

SO I easily feel the marks in the upper part of the marked section, but not so easily in the bottom.

 

I would go ahead and polish them. The lip of the oil seals are undersized enough to allow for some removal of material. If they were ploished before and end up being too undersized to seal then all you are out is your time. If they still leak you an start shopping for replacements. If they just weep a little (no pooling or dripping) I'd go ahead and ride with them while looking for a deal on a set of forks.

I polish starting with 1000 grit wet-or-dry (used dry), and work up to 2500 grit.

 

Do these wear areas actually travel thru the oil seals? Not the entire upper chrome tubes move thru the oil seal area; in fact, the forks spend much more time in compression than elongation.

Movement of the tube thru the oil seal will not produce that kind of wear, more likely it is movement thru the lower bushing or interference of that part of the inner (chrome) tubes with the ID of the lower (outer) tube's inner diameter.

 

Yes, these wear areas travel thru the oil seals.

I don't know what caused them , but it really looks like someone roughly buffed the the upper tubes, maybe they were a bit pitted?

 

WIth the tubes fully extended, the marks cover a 6.5 inches long area, measured from the lower tubes. There are no marks on the fiorst 10 inches measured from the fork cap.

 

Jeez, I didn't even know about 2500 grit ! The smoother i've ever used was 1500...

Do you suggest I do this polishing job by hand in circular strokes all around the tube, or working in longitudinal strokes, up and down the tube? Wet paper with water or light oil?

 

How may inches of extension will I need to reach the damper rod? 20 inches? more?

 

24" reach should be plenty.

 

That depends on what the damage to the fork is like. You'll generally want to work across the nicks to remove the rough edges. If you treat the chrome as if you were hand-buffing paint then you won't go wrong. Work on the deep scratches, then go over the whole of the damaged area until it's glassy smooth.

 

k-moe

Thanks, it will be easier to figure that out as soon as i have the inner tubes completely out.

For the moment, the damage looks like narrow, parallel, longitudinal strokes, but it may be different on the part that I can't see for the moment.

Water or oil, with paper, or does it really manner?

 

Dry. You won't be generating enough heat to harm the chrome, and there will be some fork oil on the stanchion evern after you wipe it off.

 

I reckon wet to minimise clogging

 

Yesterday, I bought a 22mm socket and one 12" extension, and planned to borrow the other one from my neighbour. This morning I tried to slide the socket in the tube, went in half an inch deep, and then almost got jammed in there!

Oh well, I imagine a 22mm socket coud be useful for something else.

I'll go see my usual machine shop guy, I have a welding job for him...

 

OK then , just to make sure, now that I removed the cap, drain the oil, pulled out spring, removed anti-dive unit and oil seal clip and metal washer and unscrewed damping rod, all I have to do is to put the lower leg in a sturdy vise and wack the oil seal out, pulling hard and quick on the upper tube, right?

Two or three strokes and it's out, right?

FIrst time, don't want to break something...

 

You don't even need a vice. Grab an end in each hand and pull the ends apart with authority (repeatedly), or put the upper back into the triple clamp (my prefered method) and use the lower like a slide hammer. Using a bench vice involves the risk of collapsing the lower (or the upper if you clamp it) if you aren't carefiul. If you do use a bench vis, pad the jaws with cardboard and a towell.

 

Thanks for your quick answer!

The front of my bike is not very stable so I'll go with the one-tube-in-each-hand-method, doesn't matter if it takes 5-6 wacks, i'm not in a hurry.

Is it important that parts of the LH leg returns in the same leg or may I mix parts without any problem?

 

Keep the internals with the fork they belong to. They have worn in together.

 

All right, I'll put big baggies on my list.

 

Just do one fork at a time. They'll only be apart for 5 min.

 

Well, thanks for the advice, but I haven't ordered my new parts yet, I wanted to see what I have to replace before.

So they will be apart for several days, at least. :wink:

 

There are a few deeper scratches on each tube that will need the use of 400 grit dry paper to begin, because the edges of the srcatches are sharp.

And for the area with sanding marks, I think i'll have to start with something more agressive than 1000 grit wet. I gave it a try this morning and got little results after a sustained effort.

 

I'd like to add that k-moe was darn right, nobody needs a vise to separate the upper and lower leg, one hand on each end, two wacks and pop! it went out easily...actually a bit too much easily because a part flew away, but luckily not too far.

I had a better control on the strength to apply when I did the second fork.

 

the best way i've found to get nicks out of forks legs is one of those knife sharpeners with the ceramic sticks and a magic marker.
go over the scratch with the marker so you can see what your doing then use the ceramic stick like a file. When the black is gone that went to the bottom of
the scratch, it's done.
it works on little rust spots too

 

Some nicks are deep enough that filling them with epoxy is a better choice. Unfortunatey I can't give you an idea of exactly when filling is the best choice; from my perspective that is a judgment call.

 

Thanks Polock for the tip.

Nicks I have on my forks are too deep to be filed out. I'm concerned with the sharp edges only because I'm afraid they could ruin my new oil seals while installing them, no other reason, these nicks aren't in the section the oil seals travel.