'76 r75/6

[cseltz]

I have just finished (so I thought) the rebuild of my front forks. They had never, as far as I could tell, been serviced and were "squishy". In addition, they were a bit sticky. I did not remove the stanchions from the yoke but replaced the springs and seals. The wipers appeared to be fine so I did not replace those. In the box of parts that was supplied by Max BMW, there were 2 white plastic bushings that fit nicely on top of the damper rod (piston) between the piston and the bottom of the spring (not the spacers that go on to of the springs). There was no such part in place when I took the forks apart but there was a substantial amount of sludge including a bunch of plastic chips that looked like they might have, at one time, been those bushings. Once I had the whole thing back together, I pushed the front axel through and moved the sliders up and down. They move smoothly without a lot of resistance. After that, I installed the springs, torqued down the guide support, added oil and put the front wheel back on. I didn't tighten the axel. When I took the bike off the center stand, the forks hardly move at all. They are very stiff. If I move the bike forward and apply the front brake, the forks compress and stay that way. Doing the same in reverse, they extend and stay that way. Back on the lift, springs out (wheel off) they slide up and down with pressure from a couple of fingers (up). Gravity and spring from the gators extend them. There must be something simple that I am missing. Can anyone tell me what!?

Thanks,

Chip

 

[lmo1131]

First, have you read Duane Ausherman's treatise on front forks? See> http://www.w6rec.com/duane/bmw/forkseal/index.htm

Some reference images:

Note: #7 in the above image.

Note: #9 in the above image (2 req'd./ leg)

Note: #9 in the above image.

Is/are the spring(s) and balls (#20 & 19 in the first image) working smoothly. It sounds like the oil is not able to move through the valve assembly. You did not mention what weight of oil your used. With out the axle tightened the sliders could be dragging if the stanchions are not square and parallel. Again, ref. Ausherman's article.

 

[dennisdarrow]

I have never gotten one of the "kits" for a /5 or /6 fork rebuild but have been in there a couple of times. How thick were these "white" parts that you refer to. That sludge you talk about is probably those that have disolved. Actually they go on the very bottom of the forks. For me, I take off the bottom of the fork tube and go in that way to replace seals and such. Those "donuts" or actually bottom "bumpers" or stops. Again, they go just inside of the caps as you put it back together, being the last part you put back in. Of course the last part is actually the copper squish rings; but they are a given...........Anyway, that for me, is what I think is going on for you......NO diagram or anything???..........God bless......Dennis

 

[cseltz]

# 7 is the part that was in the kit from Max but not in the fork assembly when I took it apart. As I see it, that part should be on top of the damper rod piston and directly under the spring. #9 in your diagram is between the 2 threaded nozzles. There appears to be a #10 in the diagram that would also go between those 2 threaded nozzles but there was nothing but the metal buffer there and it looks like there would be no room for anything else anyway. The buffer ring at the bottom (flat on the top and rounded on the bottom) did go back where it belonged. I did not take the bottom off the damper rod but the ball and spring appeared to be clean and the spring and sleeve at the top of the damper rod worked smoothly. I did look at Duane's article on fork alignment prior to starting but I did not see the section on seal replacement. It looks like I am going to tear the thing down again and do the complete alignment job. I did check for flatness with a pane of glass and it was fine but I don't have the instrument for checking the parallel. I have the gauge and can make up the instrument. Though the forks worked much better before I started, I did remove the guide supports in order to replace the springs and that obviously threw everything off. At least it's only January! Sorry Dennis about the lack of pictures and diagrams. I am even more inept at computer work than I am at mechanics! Thank you both for your insight.

 

[cseltz]

Also, I used 7.5 weight oil (BMW brand) from Max. Rusty at Max BMW had the whole set of parts including the oil packaged together. He recommended the new progressive springs. Given the apparent disintegration of the part #7, the springs had to come out anyway.

 

[44006]

"I didn't tighten the axel"

Sticking you describe is usually caused by fork tubes not being parallel
Suggest:

Put it back together with the wheel and axel as before

Tighten the big nut on end of axel so wheel and axel rides firmly attached to one leg

Leave other end of axel loose in the pinch bolt hole on other end of axel

Now work forks as a pair up and down while tapping loose pinch bolt fork leg in or out till you get smooth action

Then tighten pinch bolt

 

[cseltz]

"I didn't tighten the axel"

Sticking you describe is usually caused by fork tubes not being parallel
Suggest:

Put it back together with the wheel and axel as before

Tighten the big nut on end of axel so wheel and axel rides firmly attached to one leg

Leave other end of axel loose in the pinch bolt hole on other end of axel

Now work forks as a pair up and down while tapping loose pinch bolt fork leg in or out till you get smooth action

Then tighten pinch bolt

Thanks, I will do that tomorrow and post the results.

Chip

 

[cseltz]

"I didn't tighten the axel"

Sticking you describe is usually caused by fork tubes not being parallel
Suggest:

Put it back together with the wheel and axel as before

Tighten the big nut on end of axel so wheel and axel rides firmly attached to one leg

Leave other end of axel loose in the pinch bolt hole on other end of axel

Now work forks as a pair up and down while tapping loose pinch bolt fork leg in or out till you get smooth action

Then tighten pinch bolt

This worked well. I got everything back together this afternoon and the front end feels much better. Thanks to everyone for the advice.

Chip

 

[SCBuckeye]

Be sure you properly install the axle so that when tightening the nut to proper spec, you don't have the squeezer on the other fork tightened where when tightening the axle nut you are not "pulling" the far fork together into the other fork, making them un-parallel. This would cause a bind on the two forks together.

Also, without the fork spring in, make sure each fork slider (after being properly oiled) will smoothly run up and down. Then put the springs back in and tighten top caps. Then do the proper procedure for the axle.

 

[cseltz]

Be sure you properly install the axle so that when tightening the nut to proper spec, you don't have the squeezer on the other fork tightened where when tightening the axle nut you are not "pulling" the far fork together into the other fork, making them un-parallel. This would cause a bind on the two forks together.

Also, without the fork spring in, make sure each fork slider (after being properly oiled) will smoothly run up and down. Then put the springs back in and tighten top caps. Then do the proper procedure for the axle.

Thanks, That is the order I used and it worked well. My big mistake was not tightening the axel nut on the first go around. It was just as well though because I misread the drawing regarding the location of one of the parts I was replacing so they had to come apart again. I appreciate all the help (need all I can get!).