1978 R100/7 Front Fork oil change only

I have a 1978 R100/7 and all I want to do is drain the oil out of the front forks and refill.

I have Clymer's manual, and it seems to only describe a complete tear down, not just an oil change.

Is there a way to just drain and refill without a tear-down?

According to that manual, there are 5 different possible forks (probably because it includes a variety of bikes). Mine appears to be the one they call a "Type I."

They have rubber inserts on the bottom that plug into a large nut that is screwed on the bottom end of each fork. Do I just unscrew this large nut, or does the nut and allen socket first need to be removed which are inside that large nut and covered by that rubber insert?

Also, where on the top of the forks does one open and pour in the new fork oil?

If there is some video or an article I would appreciate that as well.

Thanks,

No need to remove the big nut. Remove the rubber plug on the bottom and the small cap screw on the top of the fork. Inside the bottom you will see what looks like a threaded section sticking out with an allen wrench hole in the bottom. (as you described) Around it is a nut, and under that nut is a crush washer. To remove the nut I have a socket that fits the nut (forget size now) that is ground down on the edges so I can put an open end wrench on it and run the allen wrench through it. Do not turn the allen wrench, only the nut.

Remove the nut on one side only. Oil will not come out because the spring is still pushing down on the fork sealing it from allowing the oil to come out. Put the allen wrench in screw and push up, it is pushing against a spring but it should go up and the oil MAY come out. If it doesn't do not worry. If it does, drain it and then do the other side the same after replacing the crush washer and nut.

If the oil does not come out, often the case due to junk in the bottom, remove the nut on the other side, but only after you either block the wheel to keep it from falling, or have a friend hold it. The fork assembly will fall down with the wheel and oil will gush out making a mess, so use something to catch both sides. Simple, but messy.

Reverse to reinstall.

Hope this helps.

Wayne

The only thing I would add to what Wayne said is in answer to your question about where to put the new oil. There are chrome or aluminum caps on the top to each fork tube (underneath the handlebar). The unscrew using the pin wrench from the tool kit (or something like it). Put the oil in the holes that the caps screw into. Easy to see if you look at the front suspension diagram for your model in the Max BMW parts fiche. I don't have my notes with me, so can't remember quantity, think it is 235mm each side for the drain and refill. Somebody else will jump in with confirmation or correction.

Barron

I have the same bike. The nut around the threaded rod at the bottom of the fork is probably 12mm...I've been using a 1/2-inch socket held by a pair of vise grips so I can run the allen wrench down the middle to stabilize the rod as the nut is loosened/tightened.

As for filling, my forks don't/didn't have a chrome cap, just another allen bolt in the central fill hole. It's a bit of a pain to get oil in that tiny hole. The problem is that oil wants to get in but the air has to escape for that to happen. I've tried just filling the small well at the fork cap with oil and let it trickle into the fill hole...takes forever. I think I've found a very small funnel which helps speed up the process. You might look at your favorite feed store and see what they have in the way of animal feeding syringes...often times you might find one that's big enough and you could could down the nipple...that way you can just about fill the syringe and squeeze the oil in that way.

toooldtocare said:

but only after you either block the wheel to keep it from falling, or have a friend hold it. The fork assembly will fall down with the wheel and oil will gush out making a mess, so use something to catch both sides. Simple, but messy.

Reverse to reinstall.

Hope this helps.

Wayne

Click to expand...

Why are you leaving the wheel in the fork when changing the oil?

No need to remove the wheel since the wheel assembly does not prevent the the oil from coming out. It is heavy though, which is why I warn to block it if you have to remove both bottom jam nuts to allow the fork assembly drop down a bit. I use a board under the wheel as a stop. When drained I ask a friend to pull the assembly up the 1/2 inch or so the wheel fell while I replace the nuts.

Also, my bike does not have the chrome cap either, just the small Allen screw at the top. My R90S did though.

To put oil in I use a mini-vac. I remove the tube from the vacuum side of the pump and put it on the pressure side. Measure the fluid in a container then transfer it to the mini-vac collection cup and pump the oil in through a tube with one of the mini-vac adapters. Takes a couple of fills of the cup. Whole process to do both sides is about 15 minutes if you can get the top fill screw off without removing the handlebars, difficult on my bike because of the flat bars.

Wayne

edit, my took kit, Mini-vac with line hooked to pressure port on pump. On other end of collection cup adapter to fit small hole in top of fork tube. Also, tube inside cup on the output side so the cup will empty. Socket ground flat and open end wrench to hold it, allen wrench, and measuring cup. Also shown, a now stained carpet. Hope my wife does not notice. You would think she would get used to it after 42 years of marriage.

Final msg.

20774 said:

I have the same bike. The nut around the threaded rod at the bottom of the fork is probably 12mm...I've been using a 1/2-inch socket held by a pair of vise grips so I can run the allen wrench down the middle to stabilize the rod as the nut is loosened/tightened.

As for filling, my forks don't/didn't have a chrome cap, just another allen bolt in the central fill hole. It's a bit of a pain to get oil in that tiny hole. The problem is that oil wants to get in but the air has to escape for that to happen. I've tried just filling the small well at the fork cap with oil and let it trickle into the fill hole...takes forever. I think I've found a very small funnel which helps speed up the process. You might look at your favorite feed store and see what they have in the way of animal feeding syringes...often times you might find one that's big enough and you could could down the nipple...that way you can just about fill the syringe and squeeze the oil in that way.

Click to expand...

My forks are exactly as you describe yours are!

Here is what I did. I made my own socked with flats. Those Taiwan tools that you occasionally find along side the road sure do come handy sometimes. I used a recovering 12 MM socket!

1. Removed rubber cap on bottom of both forks.

2. Removed nut using my socket, wrench and allen wrench

3. Took off the bottom large nut using the sheet metal wrench supplied in my original BMW Tool kit.

4. Took out the Allen bolt on the top of the fork

5. Thoroughly cleaned out the bottom large nut.

6. Let oil completely drain.

7. Put the bottom back together

8. Slowly add recommended amount of fork oil.

9. Put top Screw back in.

After doing the first fork, did the second the exact same way.

Much easier than I thought it would be!

Thanks to all of you!

One last thing:

When refilling through that small threaded hole at the top of the forks I used one of those quart bottles that gear oil comes in. They usually have a cap with a filler point that you cut off at the appropriate place to provide you with the hole size you want.

I did that, and wow, refilling was easy. I used a combination of 5W and 10W oil, but I think it only took about 1 minute on each fork to stand there and refil.

Be Careful Tightening The Screw Plug.

The screw plug bolt is 13mm. I use one of Joe's Tools fork drain tools.

DO NOT OVER TORQUE THE NUT! Is very easy to shear off the screw plug. DAMHIK.

JIMMYLEE said:

1. Removed rubber cap on bottom of both forks.

2. Removed nut using my socket, wrench and allen wrench

3. Took off the bottom large nut using the sheet metal wrench supplied in my original BMW Tool kit.

5. Thoroughly cleaned out the bottom large nut.

7. Put the bottom back together

Click to expand...

For me, after doing this MANY times over the years by following the instructions in the "Owners Manual" provided with the bike, I merely:

take off the discussed nut from the bottom of each fork
place a container under each fork leg
pull down on the forks and catch the escaping fluid.
roll the bike off the center stand which compresses the forks while guiding the bolt into place
reinstall the nut
fill from the top

When you took off that bottom cap, #3 above, did you:
check out, clean up the goop, and install/reinstall the rubber/plastic bumper?

When putting it back together did you use NEW copper squish washers? That is the big reason for NOT removing the big cap. If you do, and usually only for checking out the bumper, one typically replaces ALL washers as they are pretty much a one time use if they are disturbed.............

Glad you got it done........God bless.........Dennis