Fork rebuild and rear shock replacement???

[10drum]

Greetings, This old R65 is running pretty good. It's time to improve the ride. Do I need anything other than seals to rebuild the front forks? I went into shock, when I saw the BMW price for the rear shocks, no pun intended. I did check MOTO Bin and they have a pair for L110 (probably $150) shipped. Thanks for all replies.

[Tony Smith]

Greetings, This old R65 is running pretty good. It's time to improve the ride. Do I need anything other than seals to rebuild the front forks? I went into shock, when I saw the BMW price for the rear shocks, no pun intended. I did check MOTO Bin and they have a pair for L110 (probably $150) shipped. Thanks for all replies.

For the front forks, I'd suggest new springs and bump stops, once you have them apart you will know whether you also need damper rod piston rings - buy 3 of them for spares, you or someone you are helping will need them one day.

The next bit depends on your weight.

If you are under 75kg just buy either R65 or R80ST springs.

If you are between 75kg and under 90 kg, buy the same springs and also find yourself a hollow alloy handlebar you can cut spacers off.

If you are over 90 kg, buy R80ST HEAVY DUTY springs and still make sure you have a source of spacers.

Fluid wise, without wanting to re-visit past discussions too much I recommend as follows:-

Under 75kg - 5w Castrol Fork fluid
Under 90kg - 75/25% mix Castrol 5 and 10 weight
Over 90 but under 110kg 50/50% 5 and 10 weight Castrol
Over 110kg and under 125 75/25% 10 and 5 weight
Over 125kg - 100% 10 weight

When setting front fork static drop if I were still setting up for thew track I would be looking for 10% of the total available travel in drop, but as the real world roads I ride on are much rougher than any track - I look for a 1" static drop.

My actual weight is a state secret but I have approximately 1.2" spacers on top of R80ST HD springs sources form BMW Motorworks.


For the back end - i am playing with a set of Betor Shocks at the moment, attempting to make them "better" than standard by fiddling with fluid weight. (i ordered springs heavy enough so that I have a little under 1" drop with the springs on the 2nd lowest preload.

But for "set and forget" just email Ikon and tell them what you weigh and whether you need any allowance for pillion/luggage and buy their shocks.

Ikons are expensive, but very good and are rebuildable (for that matter Betors are rebuildable too)

At the "crazy expensive" uber tech end of the spectrum, I recently found out that Fournales are still available - I have lusted after a set of Fournales for a very, very long time - you will also need to buy a shock pump capable of at least 300psi if you buy Fournales.
 
Best of and all that.

[10drum]

Wow, Tony, Thanks for the reply, and I was just hoping to clean the dampeners, buff the stanchions, replace the seals/fliud, and install inexpensive aftermarket rear shocks.

[montmil]

Both of my R65s are happy with Hagon shocks. Relatively inexpensive but the quality is there.

Try talking with Dave at Dave Quinn Motorcycles. He will want to know: 1) Your honest, ATGATT ready to ride weight; 2) Mostly solo or w/pillion; 3) Luggage or not; 4) What MC you have. With that information, Dave will install springs to fit your particular ride.

http://davequinnmotorcycles.com/

As a new-to-you motorcycle, it may be a good idea, with the legs removed, to clean out the lowers. Those small drain screws -which are easily stripped by heavy-handed folks- are fitted higher than the bottom of the fluid reservoir. You'll likely find some nasty stuff.

Do check the bump stops. Earlier bits were a rubber-ish compound that was destroyed by newer fork fluid formulas. Sludge in the lowers is what passes for their remains. New stops are a soft nylon-like material.

Here's what was in the fork lowers of my 1981 R65.



To help keep the new fork seals happy, be sure to replace the felts that fit in the rubber cups.

[Tony Smith]

Wow, Tony, Thanks for the reply, and I was just hoping to clean the dampeners, buff the stanchions, replace the seals/fliud, and install inexpensive aftermarket rear shocks.

Your bike is a minimum of 31 years old and you don't know its history. Do it right and do it once. Cut corners on the job and do it at least twice.

I am the greatest cutter of corners you will ever meet - but some things, like brakes, suspension and tyres are simply too important to mess about with.

[mrclubike]

Where are you guys getting new piston rings
I have yet to see anyone have them for sale  
Are you just going to a hydraulic shop and matching some thing up
in Teflon

[nhmaf]

Don't forget new crush washers for the drain plugs and for the large Allen bolts that are on the inside, bottom end of the  sliders (they hold the slider onto the damping assembly).     They are only about 11 cents, but I've found trying to reuse them can result in leaks... and having to take everything apart again to replace..

Piston rings for the damper are available from the BMW dealer  - they ARE NOT cheap - I think they were ~ $8 a piece (and you need (3)) to do one damper rod.   Usually, the older ones are still fine and can be reused if they aren't severely worn, nicked or bent - so be careful when extracting the damper rod assembly from the sliders.  The need to be compressed carefully (you can use some sacrificial feeler gauges) when reinserting into the tube.

somewhere around here I have some pics/thread on this process.

[georgesgiralt]

Piston rings for R65 are quite cheap actually and sold by BMW . See the picture. They are sold by sets of 3 and the price is for the set.
You need two set, one for each leg  

[montmil]

I'm easily confused as my wife will confirm...

Are we now discussing engine piston rings or the thin rings found on the damper rod assembly?

[thrang]

I always make sure I have 3 set's of damper piston rings, and a spare or two the fu*ging circlips that hold the fork internals from above when I rebuild a set of r65 forks, mainly because I know if I only have enough to do the job I'm bound to have something ping and have it vanish into that parallel universe where missing socks and 9mm sockets end up!

Given you don't know the history I'd do a full rebuild and replace the bump stops, springs, washers, drain plugs and the lower bolts for piece of mind. Better to do the job properly first time out then you can be confident that the front end is in tip-top condition.

Like Monte I'm running Hagon rear shocks on mine and they do the job just nicely and don't break the bank.

[Barry]

I thought there was a view that new damper piston rings were not the same quality as the originals and that they are rarely needed anyway as the originals don't wear much.  Mine looked like they were barely run in.
All I did was re-space the gaps at 120 Deg although it's probably a futile gesture.

Someone on another forum machined the piston gap wider to take the 81 on type 247 piston rings which seal better with less stiction.  I thought that was a smart move and a relatively easy mod if you have access to a lathe.

[georgesgiralt]

Yes Barry, the new rings may be worse than the original but given I had only two instead of the required 3 I was forced to replace them. So far, 10 k km after they are still going strong.
As one side is making noises I bet I have, again, a rubber stop failure. I think BMW has not yet found the right rubber/plastic to resist the current anti-swell fork fluids...
IRC the bumper failure were :
1) the bumper disintegrated in very small very hard cubic bits (like a Securit windshield)
2) the bumper became a black goo in the bottom of the fork, clogging the little draining hole
3) the bumper became very very hard and broke in parts, some of them drained with oil.
4) this current bumper is making noises so I bet it is dead but have not found how yet...
I'm becoming very fast at dismantling/re-assembling an R65 fork...  :-?

[Tony Smith]

 I thought that was a smart move and a relatively easy mod if you have access to a lathe.

I bought the new model "rings" and set up the lathe ready to do the deed, and stopped.

After measuring everything up and contemplating where the various forces act I decided that there might not be enough material left for it to be safe. If I ever end up with some spare damper rods I will modify one and then subject it to some non-destructive testing before I fit it to my motorcycle.

[Tony Smith]

Where are you guys getting new piston rings
I have yet to see anyone have them for sale  
Are you just going to a hydraulic shop and matching some thing up
in Teflon

Motobins Part No.29000

[mrclubike]

When I rebuilt my forks the rings were very worn but didn't see them on the R65 parts break down so i didn't replace them but i know i need them.