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R75/5 SWB front fork rebuild

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schrader7032
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Re: R75/5 SWB front fork rebuild

Post by schrader7032 »

Have you completely assembled the forks without the springs? If things are aligned well you should be able easily slide the wheel up and down. If not then you cannbegin to look for a problem.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

Mcgee
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Re: R75/5 SWB front fork rebuild

Post by Mcgee »

Yes, I completely had everything assembled including the fork brace/fender holder and torqued before installing the springs. The axle turned freely throughout the range of movement. I tightened the pinch bolts while the sliders were at the top of their range and checked how the sliders moved again. All seemed great.
Also, when I torque the fork nuts I use a bar to keep from torquing against the fork stops.
I am thinking about new fork tubes and maybe damper rods. I don't like to throw parts at things not knowing what is wrong tho.
Someone said that I could possibly have a bent triple tree. Except that I had everything aligned and parallel. Not sure about that one, but?
Thanks,
Mike

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Re: R75/5 SWB front fork rebuild

Post by Mcgee »

The motorcycle I am having stiction problems is 1977 R75/7.
I have been carefully inspecting components since I don't seem to solve the problem.How much tolerance is allowed with the fork tubes runout? I discovered one tube is out .002 in. and the other around .015 in. The fork damper rods seem to be straight, but the piston with the slider rings on the damper rod has around .006 in deviation.
Any ideas?
Thank you for your response,
Mike McAllister

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schrader7032
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Re: R75/5 SWB front fork rebuild

Post by schrader7032 »

My Haynes manual mentions maximum warpage of 0.0039". Not sure if that's the same as runout.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

Mcgee
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Re: R75/5 SWB front fork rebuild

Post by Mcgee »

Thanks Kurt! I think it is the same as I was thinking. 0.0039" is more than I have at .002". Maybe the forks are good to go?

Mike McAllister

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schrader7032
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Re: R75/5 SWB front fork rebuild

Post by schrader7032 »

Not sure...you did give another measurement of 0.015" which is much larger than 0.0039.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

Mcgee
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Joined: Sun Dec 07, 2014 8:20 am
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Re: R75/5 SWB front fork rebuild

Post by Mcgee »

Oops, I wrote that down wrong. I meant 0.0015. Thanks for the heads-up.
Mike McAllister

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Re: R75/5 SWB front fork rebuild

Post by Mcgee »

A follow up on my stiction problems. Finally got it working as it should, or a least I think as it should, ha. The main one thing that I discovered that probably was contributing to my stiction was a polyurethane bushing that I was installing in the wrong place inside the fork tube. According to BMW parts fiches from different sources, it showed the said bushing installed just below the mainspring on the damper rod. It was supposed to be installed below the piston on the damper rod. After I did that all was well.

Thank you all who responded. Always a great help! I was beginning to think maybe I should hang up my wrenches. Ha.

Mike McAllister

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