Changing fork oil

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swarrans
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Changing fork oil

Post by swarrans »

My 82 CBX seems to have been leaking oil from one of the fork drain screws whilst being stored over winter. I don't know how much I have lost (probably not a huge amount as a little oil on the floor goes a long way!) but I'd like to drain both legs and re-fill to be sure.
I know the correct procedure via the manual (and the suggested modified amount via Dave's posts) but can I just remove the drain and pump the old oil out and put back in say 305 cc to avoid having to do a front end strip down?

Simon

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Re: Changing fork oil

Post by daves79x »

I'd check higher for your leak - like the fork seal. I'd bet it's not the drain screw. If that's the case, you'll need to remove the legs and install new seals. Even to do what you suggest, the legs almost have to come out.

Dave

Oh - and if you find it's the fork seal, check the brake pads on that leg for contamination. Oil usually runs right through the caliper and ruins the brake pads as well.

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Re: Changing fork oil

Post by Larry Zimmer »

Ditto on Dave's reply. I took that class at the academy of "Been There". Another 'tip' for you with your '82, check the front brake master cylinder closely for any 'suggestion' of a leak where the lever pushes on the rod. Like any dampness around that seal. It can develop the weepyest of a leak, after 30+ years, that will drip onto your fairing in very small amounts. The paint and the base plastic don't like that stuff. Believe me! If you do suspect anything with the master cylinder, TIMS has an excellent rebuild kit.
Larry Zimmer
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Re: Changing fork oil

Post by swarrans »

You were both right of course - I took her for a quick spin and one fork seal is leaking badly.

I'm struggling with whether to do it myself or not - garage will charge about $150 but I don't have a seal driver so would be forced to improvise.

If I do it myself do you recommend putting the new seal in before the stanchion and using a suitable socket to drive it in or do I have to put it in after the leg is attached and therefore either buy a fork seal driver or try and find a suitable OD and ID tube?

Can I assume I just need to buy the seals themselves or should I get new retaining rings and dust seals?

I'm fairly good at doing my own maintenance but I just figure it is quite easy to damage the seal putting it in...

Many thanks

Simon

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Re: Changing fork oil

Post by swarrans »

I have already decided to do it myself and have bought a seal driver tool (Impatient much?!)

The shop manual (pages 217 to 220) is a bit confusing on the disassembly process - it says you can remove the seal without separating the inner fork tube and slider but I'm not too sure how it is achieved? Edit: I think I understand now - they are saying fill the fork tube with fluid and then block the air connection and use a press to force the seal out. I wonder how much force will be needed?

Simon

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Re: Changing fork oil

Post by daves79x »

Time out. There are quite a few threads here about this subject. Short version is use the fork tube as a slide hammer to remove the seal/bushing. Tube had to be installed when seal is driven in. Then fill tube to 6 inches from top with spring out and tube collapsed. This is more than spec. Use 10wt fork oil. Pretty much it.

Dave

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Re: Changing fork oil

Post by Larry Zimmer »

Little tip on seating seals. Install the seal to the point where the top edge of the seal (the surface the snap ring sits against) is even with the top of the snap ring groove. Then, install the snap ring into the bore against the top of the seal. Now, take the seal driver (a 2-ft piece of pvc pipe works good) and drive the snap ring down until it snaps into its groove. You will now have a seal that is in square and flush against the snap ring.
P.S. Be certain to check your slider tubes for scratches and nicks. Finish polish with 600 grit wet with oil. Be certain to polish AROUND the tube NOT vertical up-and-down.
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Re: Changing fork oil

Post by swarrans »

OK many thanks and sorry for covering old ground...

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Re: Changing fork oil

Post by Larry Zimmer »

No problem what-so-ever, Simon. Let us/me know if you have any questions or problem finding something in your search. Glad to help.
Larry Zimmer
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Re: Changing fork oil

Post by steve murdoch icoa #5322 »

swarrans wrote:OK many thanks and sorry for covering old ground...
Even when "covering old ground" there is quite often a new take or new solution to the problem.
That and i have c.r.s. syndrome so a reminder is usually in order.
Ask away.

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Re: Changing fork oil

Post by swarrans »

OK since you don't mind me asking daft questions (!) how do you get the socket bolt out that goes into the bottom of the fork piston? Initially it started to undo but I suspect the piston itself is now just spinning so I can't get it out (and therefore can't do the slam hammer technique). Will it help if I temporarily re-assemble the spring and fork cap to put some load/resistance on the piston or is there another technique. I've tried with an air rachet thinking that the pulses might help but it hasn't worked...

Thx

Simon

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Re: Changing fork oil

Post by NobleHops »

swarrans wrote:OK since you don't mind me asking daft questions (!) how do you get the socket bolt out that goes into the bottom of the fork piston? Initially it started to undo but I suspect the piston itself is now just spinning so I can't get it out (and therefore can't do the slam hammer technique). Will it help if I temporarily re-assemble the spring and fork cap to put some load/resistance on the piston or is there another technique. I've tried with an air rachet thinking that the pulses might help but it hasn't worked...

Thx

Simon
Yes, Simon, that may work. Customarily I start with that bolt - break it loose with the impact before any other disassembly, retighten it by hand just till it won't make a mess, then remove the fork cap and proceed with the remainder of the disassembly.

The alternative is either a fancy tool, or the "factory broomstick": Take a thinner broomstick and sand it to a taper on one end put that down along the wall of the stanchion and wedge it between the damper rod and the stanchion and then loosen the bottom bolt.
Nils Menten
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Re: Changing fork oil

Post by swarrans »

Many thanks!

All finished now and thank God no leaks and she passed her MoT (UK roadworthiness test)

Simon

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