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R75/5 SWB front fork rebuild

maddrobh
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Re: R75/5 SWB front fork rebuild

Post by maddrobh »

Ok, I know what the red washers are now.
‘71 R75/5, ‘21 R1250RS, & a couple of brits

maddrobh
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Re: R75/5 SWB front fork rebuild

Post by maddrobh »

Ended-up fitting progressive springs, 250 cc of 7.5 wt fork oil. Seems to be very good. May add the other 30 cc of oil.
‘71 R75/5, ‘21 R1250RS, & a couple of brits

maddrobh
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Re: R75/5 SWB front fork rebuild

Post by maddrobh »

20241111_135227.jpg
‘71 R75/5, ‘21 R1250RS, & a couple of brits

Mcgee
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Re: R75/5 SWB front fork rebuild

Post by Mcgee »

Nice looking bike! I have been rebuilding my 77 R75/7 front forks and replaced the steering head bearings while I was there. They need replacing for sure.
After I put things back together, the forks hardly worked! With some research, I found that by torquing the upper fork stanchions against the steering stops that I misaligned the forks! Had really bad stiction!
I'm in the process of realigning the forks then retorque.
My question is how did you torque the fork stanchions?

Thankyou, Mike

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schrader7032
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Re: R75/5 SWB front fork rebuild

Post by schrader7032 »

About 2/3 the way down Snowbum's page he has a discussion about how to torque the top plate using a screwdriver as a reaction bar:

https://bmwmotorcycletech.info/frontforks.htm
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

maddrobh
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Re: R75/5 SWB front fork rebuild

Post by maddrobh »

I torqued the slider bottom caps with the fork leg in a soft-jawed vice. Sealed by a thick, soft copper crush washer and I used a little non-hardening sealant (Well Seal). The torque value was a little under the quoted value. I then secured the sliders to the stanchions using the gaiters (as per manual) and slid the sliders into the yokes. I had not touched the head bearings which are fine. After tightening the front wheel and fork brace, I did up the pinch bolts in the lower yoke, and put a little sealant on the fork top plugs. I did these up against the steering stop by tapping the tool kit spanner with a hide hammer; the same way I took them off. I used new copper washers but no sealant on the top caps, tightened with the tool kit pin spanner.

So far, the forks seem fine, and without stiction. I will check the top cap tightness after some miles, but I’m happy to do that by ‘feel’.

Two other things: I used the two feeler gauge method to get the damper pistons into the stanchion. Fork leg in vice, 25 thou feelers thin enough to ‘get in’, strong enough to compress the damper piston rings. Also, I put the stanchions back into their sliders with the former rotated 180 deg from when I took them out - as suggested by another above.

For your misaligned forks, there are certainly things written by people far more knowledgeable than me. However, you could try the ‘old’ method. Loosen everything off, pump the forks up and down a few times with the wheel against a wall, the tighten-up from the bottom upwards: wheel, fork brace, pinch bolts, top plugs, fork yoke top nut. (I’m sure that some will disagree with this, but it’s what I do on my old Triumph.)
‘71 R75/5, ‘21 R1250RS, & a couple of brits

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r67boxer
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Re: R75/5 SWB front fork rebuild

Post by r67boxer »

Brook's Airhead Garage has a thorough video for installing forks and aligning same on an '83 R100.

https://www.youtube.com/watch?v=Oyhg1wYLcG8

K

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drpetemurray
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Re: R75/5 SWB front fork rebuild

Post by drpetemurray »

Mcgee wrote:
Mon Nov 11, 2024 11:33 am
Nice looking bike!
My question is how did you torque the fork stanchions?

Thankyou, Mike
After aligning the forks with your preferred method, I use a 2-foot piece of Black pipe ( Gas Pipe to stabilize the top tree ) through the handlebar clamps. You have to offset the pipe to gain clearance to the fasteners. First, torque the stem nut and then the cap nuts incrementally.
Brook is a bit overkill in the alignment process. These forks have a ton of flex when riding and are not always true when in motion. I will say that when the forks compress, they flex less due to tube overlap.
PeteM
Stroudsburg,Pa
73 R75/5 , 1014 RTW, IBA 359

Mcgee
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Re: R75/5 SWB front fork rebuild

Post by Mcgee »

Thanks everybody for your replies! Will get to work on the forks again tomorrow, hopefully. Raining a lot around here, PNW. So no real hurry. I think I will just go over everything again methodically and pay attention to to the details. I will not tighten the fork nuts and center nut against the steering stops again, Ha.
Mike

Mcgee
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Re: R75/5 SWB front fork rebuild

Post by Mcgee »

So far I have been having a bit of trouble getting these forks to keep from sticking! My bike is a 1977 R75/7. I followed Duane Ausherman's and Randy Glass's procedure for aligning forks very carefully. Just got it back together again after a few tries and again, no joy!
I am at a loss why these forks won't work. I have checked everything for straightness with dial indicators. Had the fork tubes parallel and checked with a piece of glass even after everything was torqued. It did take a while to get everything aligned.
I did install a new rebuild kit from EME and steering head bearings.
I have no history on the bike and it sat for about 10 years. I believe it has around 65,000 miles on it.
Can the fork tubes have uneven wear inside? They looked good when inspected them, at least to me.
Also, I checked the fork dampers for straightness and the top plate.
I shimmed the fork brace after I found out when I torqued it up it pulled the fork tubes inward. All good on that.
Any ideas out there?

Thank you,
Mike/mcgee

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