R75/7 Front Fork questions

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Gurstang
Posts: 12
Joined: Wed Aug 16, 2017 10:21 pm

R75/7 Front Fork questions

Post by Gurstang »

I am going to do a rebuild on my forks. They are not smooth, have sticktion and make springy sounds.

When I compress them off the motorcycle, and they spring back, it sounds like the fluid is cavitating.

I have one of the forks apart, I have not taken either end off of the damper rod.

My Haynes manual says the damper rod must be removed from the lower end of the stanchion. For me, it slid right out of the top, if I Invert the stanchion and remove the end cap and spring. Is that normal?

The rubber/nylon bumper at the very bottom of the fork slider crumbled in my hand. I did not find any type of nylon bushing which should be between the damper rod and the stanchion. Could this have crumbled away? It is item 7 in the image below. Could that be why I hear spring sounds when I compress them?
Image

I also do not have number 10 from the image. The part is listed at Max BMW shown below. Since it is metal, I am assuming it was never present.
Image

I have seen a few rebuild kits and they seem very straight forward. I don't think I will take apart the damper rod. The ball check value works. I am hoping I can clean any bits out of it with compressed air.

Any other advice?
richard t
Posts: 705
Joined: Tue Aug 03, 2010 10:35 pm
Location: Crescent Oklahoma USA

Re: R75/7 Front Fork questions

Post by richard t »

I have a socket I cut flats on for a wrench and I remove the nut on the bottom of the rod and pull the bottom off but your way works too those spacers will turn to mush over time
Wobbly
Posts: 300
Joined: Mon Aug 07, 2017 8:48 pm

Re: R75/7 Front Fork questions

Post by Wobbly »

Can't help with the internal parts, but will suggest you might want to try some synthetic fork oil in an effort to reduce sticksion and make internal parts last longer. You'll want a product like Bel-Ray 7W fork oil, or any synthetic between 5 and 10W.
After 20 years as a professional bike mechanic and 30 years as an engineer I know just enough to be dangerous !
ME 109
Posts: 7306
Joined: Tue Aug 03, 2010 3:00 am
Location: Albury, Australia

Re: R75/7 Front Fork questions

Post by ME 109 »

Ideal time to check the fork legs for perfect straight, and if they are, check the triple tree for straight with the ‘straight’ fork legs.
Lord of the Bings
Gurstang
Posts: 12
Joined: Wed Aug 16, 2017 10:21 pm

Re: R75/7 Front Fork questions

Post by Gurstang »

I finished the fork rebuild. What difference it makes. The 2nd leg wouldn't even drain after I removed the nut and pulled the piston out of the lower leg. There was so much material in there from the deteriorated parts.

Now I can use the side stand without the bike tipping over, since it will now spring back to the intended height.
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