Front Fork Service/Rebuild

[Tv]

G'day, how hard is it and do I need any special tools to service or rebuild my front forks? The ride on my ['84 R65] could be better.

How long does it take to do the job?  Thanks!

[Barry]

They are conventional damper rod forks and it's an easy enough job with no special tools needed other than maybe a long socket extension. A workshop manual or at least a diagram from one of the parts fiches is probably essential so you can see how everything fits together.  

Drain the oil

Before removing the springs try and loosen the allen screw #17 in the base of the slider. if it keeps turning this is where you might need the long socket extension to hold the top of the piston rod but you will have to remove the springs first.

Remove the top plugs which are held by a circlip under spring pressure. You will need some ingenuity or 3 hands to do the next bit  Press Down on the plug and you will see a wire circlip which can be dislodged and removed with a small screw driver. With the circlip out of the way the plug will pop out under spring pressure.

With the lower allen screws removed the sliders will just fall off leaving the damper rod behind still in the stanchion.

Remove the large circlip at the bottom of the stanchion and a shim and the valve body will fall out together withe a valve washer and valve plate in that order

The damper rod can now be removed taking care not to damage the piston rings.

Other than a good clean the only spares you are likely to need are new crush washers for the drain screws and lower Allen screws and probably the top out rubber or poly bushes #24. Might also want to consider new fork seals while the sliders are off although if they don't leak at all I would leave them in or you could do the old trick of shortening the garter spring.

[Rob Valdez 79 R65]

You will need a pair of snap-ring pliers for that bottom circlip.

Here are some threads for reading:

http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1270506405

http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1254093089

http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1287432022

[montmil]

There are a few "consumable"parts normally replaced when rebuilding and reassembling the forks; You will want fresh fork seals, felts, and the O-rings in the top plug.

It's not really necessary to remove the fork drain plug if you plan to totally strip, clean and rebuild the forks. When the lowers are removed, just pour out the old fork oil. Be sure to completely clean the interior as you will find quite a bit of fine grain sludge in the bottom of the lowers and atop the damper rod.

There are "piston rings" inside the damper assembly and these rings should be reinstalled with the ring gaps 180 degrees apart from each other.

If you are running the OEM rubber dust covers, new felts are mandatory. They are your first line of defense in the war on dust and grit. Pre-soak the felts in oil prior to fitting them in the rubber cups.

Check the fork stanchions for any tiny burrs that may damage the new seals. 800 grit Wet-or-Dri can be used to smooth any 'spurs' that you may find.

Be sure the new seals are installed square to the fork lower and that they are fully seated.

The snap ring that secures the upper fork plug does not actually fit in a machined groove; it sits in a milled "ledge" and spring pressure holds it in place. A small, flat-blade screwdriver is used to "tilt" the snap ring and then it is withdrawn using needle-nosed pliers. Mind the plug removal as you'll be working against the fork spring pressure. Eye protection is a good thing.

BMW recommends 7.5wt fork oil. I presently run 10wt in both my R65s. Be advised, the fork oil is primarily controlling rebound damping. The springs are the 'stars' of compression damping. Our R65s are not known for their superior fork action so don't expect UJM performance.

If you are considering changing over to new after-market "progressive" fork springs, many BMW peeps recommend that the best installation of these stout springs is that they be installed in a vertical position inside a 55 gallon trash barrel.

Do you have a decent shop manual? Time? For your first attempt at a fork overhaul, I would allow a full Saturday afternoon so that you might study and learn the correct procedures.

If you get lost, knock us up anytime.

Monte

[Tv]

Thanks a lot for the info.  I'll go to the BMW shop and get a kit and give it go.

[tvrla]

Has anyone installed Cartridge Emulators? I'm seriously considering the upgrade - they made a world of difference to the R80G/S.

[Barry]

I've thought about it. Not a cheap upgrade though with new shorter springs needed as well as the emulators. Not heard of anyone fitting them to R65 forks but in principle I can't see any reason why not if you can do the machining work needed on the damper rod.

If you have fitted them to an R80G/S you'll know there's no going back to stock without new damper rods.