Front fork question

[raymr]

OK. I've never worked on motorcycle forks before. Now I have the lower sliders off the stanchions. The top retainers and springs are still installed.  

At this point, I can easily replace the seals and cups. The question now is should I remove and disassemble the damper part? I'm reading mixed advice - some say leave it alone, others say to replace the o-rings and piston seal. I really don't want to pull the handlebar so I'd need to find a 36mm ring wrench to remove the uppers. I presume the cir-clip on the bottom holding in the valve body is under spring pressure. As far as I can tell, no work has been done on the fork in the past.

Hope this doesn't seem like a stupid question!?!      

[montmil]

It sounds a bit like you've begun the job by starting in the middle!

As you already know, it is possible to remove the lowers after unscrewing the large Allen screw in the bottom of the fork lower. Here's the fly in the ointment: You need to access the top of the damper rod and secure it with a socket and a 14-in extension to properly reinstall the assembly. To do this, you will need to remove the upper caps and the spring-wire circlip that retains the spring assembly.

By loosening the triple clamp pinch bolts, the upper stanchions can be withdrawn. If stubbornly stuck, a wooden wedge may be carefully tapped into the pinch bolt openings to relieve clamping pressure. Carefully!

Further work may be done with the stanchions held in a large vice and padded with wooden blocks. Watch for the damper rods and springs as they fall free from the stanchion.

The fully assembled fork legs may be refitted up through the triple clamps.

Did you purchase new felts for the rubber cups?

Good luck. Any more questions, just sing out.

Monte

[Barry]

Having gone this far I would remove the damper rods and damper valve body as there is a rubber topping out bush in there that should definitely be replaced before it disintegrates. When you mention "piston seal" there is a well informed body of opinion that says you should not replace the 3 damper piston rings as the material quality from even genuine BMW spares is not as good as the originals.

Although it's a little more awkward to remove and replace the big circlip at the bottom of the stanchion you don't have to remove the stanchions from the triple trees to take out the damper rod and valve body. I've done it both ways several times and now always do it with the stanchions in place to avoid unnecessary disturbance of the fork alignment. The big circlips will not be under pressure from the main springs if you remove the spring retainers at the top of the stanchions first. Even if you don't, if stock there is only about 1" of pre-load on the springs so the valve body does exactly shoot out like a bullet. You should not have to remove the handlebars to remove the spring retainer other than to rotate the brake lever up a little  to provide some clearance under low euro bars.

I'm confused by why you would need to use a "36mm ring wrench"

[raymr]

According to MAXBMW parts, there is no separate felt, maybe it's part of the cup?

It sounds a bit like you've begun the job by starting in the middle!

As you already know, it is possible to remove the lowers after unscrewing the large Allen screw in the bottom of the fork lower. Here's the fly in the ointment: You need to access the top of the damper rod and secure it with a socket and a 14-in extension to properly reinstall the assembly. To do this, you will need to remove the upper caps and the spring-wire circlip that retains the spring assembly.

By loosening the triple clamp pinch bolts, the upper stanchions can be withdrawn. If stubbornly stuck, a wooden wedge may be carefully tapped into the pinch bolt openings to relieve clamping pressure. Carefully!

Further work may be done with the stanchions held in a large vice and padded with wooden blocks. Watch for the damper rods and springs as they fall free from the stanchion.

The fully assembled fork legs may be refitted up through the triple clamps.

Did you purchase new felts for the rubber cups?

Good luck. Any more questions, just sing out.

Monte

[raymr]

What tool do you use to loosen the spring retainers with the handlebar in place? I've seen them called dogbone wrenches, or BMW calls it a ring spanner.

Having gone this far I would remove the damper rods and damper valve body as there is a rubber topping out bush in there that should definitely be replaced before it disintegrates. When you mention "piston seal" there is a well informed body of opinion that says you should not replace the 3 damper piston rings as the material quality from even genuine BMW spares is not as good as the originals.

Although it's a little more awkward to remove and replace the big circlip at the bottom of the stanchion you don't have to remove the stanchions from the triple trees to take out the damper rod and valve body. I've done it both ways several times and now always do it with the stanchions in place to avoid unnecessary disturbance of the fork alignment. The big circlips will not be under pressure from the main springs if you remove the spring retainers at the top of the stanchions first. Even if you don't, if stock there is only about 1" of pre-load on the springs so the valve body does exactly shoot out like a bullet. You should not have to remove the handlebars to remove the spring retainer other than to rotate the brake lever up a little  to provide some clearance under low euro bars.

I'm confused by why you would need to use a "36mm ring wrench"

[montmil]

Fork Slider 32_0297

http://store.bobsbmw.com/microfiche/BrowseParts.aspx?GroupName=Front+axle%2c+front+suspension&MBike=51897&GroupID=31


Part #4. Oiled felt wipers are the first line of defense prior to the fork seals.

Please consider adding your model year in your posts as parts vary from year-year.

Monte

[raymr]

Its a 1986 model, built in 09/85.
 

Fork Slider 32_0297

http://store.bobsbmw.com/microfiche/BrowseParts.aspx?GroupName=Front+axle%2c+front+suspension&MBike=51897&GroupID=31


Part #4. Oiled felt wipers are the first line of defense prior to the fork seals.

Please consider adding your model year in your posts as parts vary from year-year.

Monte

[Barry]

What tool do you use to loosen the spring retainers with the handlebar in place? I've seen them called dogbone wrenches, or BMW calls it a ring spanner.

It's a 1986 - I missed that.!  They have a different type of fork. I would need to look at a diagram to see what's different to the 78 - 85 models.


Edit: The 85 on forks really are different. There is a topping out spring instead of the rubber bush and the damper valve and piston ring looks completely different. There is an O ring or two in there that probably need looking at.  The spring retainers are screw in type so now I understand your need for the spanner.  Still think you might be able to leave the stanchions in situ though and drop the valve body and damper rod out the bottom.

[raymr]

I got it all back together, filled with Motul fork oil and put about 75 miles on it. The seals have been revised and are now wider presumably because the older style was wearing out quickly. The rubber dust cap fits over the top. There's nothing resembling a felt wiper on the assembly.  

Now the question is should I still be seeing an oil line on the stanchion where the seal/cap reached the highest point? The stanchion is glass smooth and the seals are in straight, but some oil is leaking out. Is some seepage to be expected?

[Bob_Roller]

No, no leakage or seepage should be there .

It may be residual fluid from reassembly, clean it off and see if it comes back .

[Barry]

In the ideal world there should be no visible oil line. It may improve with use as the seals bed in. If it's only a trace and doesn't get worse I wouldn't worry. How much oil did you put in - having the oil level too high would tend to give the seals a hard time through excessive compression in the air space above the oil.

[raymr]

200ml according to the book. The seepage may be getting slightly less. I put a light coating of grease on the seals when I put the fork back together and maybe that makes them leaky for a while(?).

[Barry]

200ml according to the book.

Which Book ?   Bearing in mind your forks are different to earlier R65's

Haynes is a a bit vague in that the volume for post 85 R65 forks is not specifically listed
however I'm almost certain they are the same as a post 85 R80 forks which take 300 ml.

[Bob_Roller]

Don't know if you have even considered installing gaiters on the forks .

I put a set on my '81 R65 a little over 4 years ago, at first, they looked out of place, but now they seem to fit in with the bike .

[raymr]

You are right. The Haynes 1986 section says all R65 chapter 6 specs are as 1985-on R80. That's 300ml. I'll have to fix that but I can't help thinking it will only make the leak worse. Thank you.

200ml according to the book.

Which Book ?   Bearing in mind your forks are different to earlier R65's

Haynes is a a bit vague in that the volume for post 85 R65 forks is not specifically listed
however I'm almost certain they are the same as a post 85 R80 forks which take 300 ml.