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Fork leak from not riding?

DonTom

DonTom

New member
I have been busy with other things and my 1971 BMW R75/5 has been on the center stand in the garage for more than six months without being moved. It gets very hot in there during the summer, perhaps 110F plus.

I recently noticed a big puddle of fork oil under the left fork, on the bottom of the front tire, tire rim as well as on the ground. A lot. Perhaps all of it leaked out, but only from the left fork.

I rebuilt the forks around three years ago, new seals then.

I never had a fork leak while I was riding the bike last summer, after the bike sat.

So what could now be happening here?

-Don- Reno, NV
 
Last edited:
Anyname said:
Make sure it's oil. I had that happen to me


and it turned out to be dog related, not oil...
Click to expand...
Well, I am sure it is fork oil. No dogs near there at my other house. But I have not taken a good look at it yet. For all I know, the nut could be loose and that would perhaps explain it.

The next time I am there, I will take a better look and replace the fork oil. I will drain each fork into a measuring cup and see how much is in each.

I expect to be riding a lot in another week, but I have five motorcycles to ride.

-Don- Reno, NV
 
SCBuckeye said:
Could it be brake fluid dripping down?

What possible "dog related" issue could this be? Hmmmmmmm?
Click to expand...
What is brake fluid? This is a 1971 TRUE classic (that means NO disk brakes & came with a kick starter!).

Anyway, I will probably take a closer look at the bike by the end of the week. It's located at my other home 15 miles away.

Perhaps I will start with a fork oil change and see how much really leaked out.

-Don- Reno, NV
 
Lift up the lower part of the fork gaiters and see if there's any trapped fluid in there.
 
If it's a big puddle, it's unlikely a seal -- the oil level shouldn't be high enough to leak from there when it sits. That leaves a leak from the bottom of the fork leg -- the washer on the drain bolt or the cap on the bottom of the fork. Both seem unlikely but after 45 years not impossible.
 
Do you still have the steering damper? Mine leaked and I thought it was the oil cooler leaking.
 
Do you still have the steering damper? Mine leaked and I thought it was the oil cooler leaking.
Click to expand...

On a '71 SWB /5, if stock, it looks like this; friction disc only, no hydraulics involved.

Damper.jpg


images
 
ccolwell said:
If it's a big puddle, it's unlikely a seal -- the oil level shouldn't be high enough to leak from there when it sits. That leaves a leak from the bottom of the fork leg -- the washer on the drain bolt or the cap on the bottom of the fork. Both seem unlikely but after 45 years not impossible.
Click to expand...
I will be looking at it more closely in a few days. Perhaps just the nut on the bottom of the fork worked loose or something simple like that. The bike is just 15 miles from here, but I have a lot of other things to deal with for the next few days.

-Don- Reno, NV
 
May just need to torque that nut on the end of the fork (not the big nut, the little one under the rubber cap)
 
ebeeby said:
May just need to torque that nut on the end of the fork (not the big nut, the little one under the rubber cap)
Click to expand...
I think that was it! That 13 mm nut was loose, not real loose, but looser than the side that didn't leak.

BTW, my rubber caps are missing on both sides.

What type of fork oil do most use in a 1971 BMW R75/5?

I will probably do that in the next few days.

I have been so busy with so much stuff lately, but I really would like to start riding that old BMW again soon.

-Don- Reno, NV
 
20774 said:
I've always preferred 7.5wt BMW oil; unfortunately they don't supply that anymore. Here's a thread of mine where I've settled on 7wt Belray...haven't made the change yet! :hide

http://forums.bmwmoa.org/showthread.php?85002-7-Fork-Oil-Part-Number
Click to expand...
Thanks, I just ordered a couple of quarts of the stuff.

BTW, yesterday, I took a much closer look. I drained the forks, but only the right fork had any fork oil in it, and it had the normal amount. The left fork was totally dry. ALL of it has already leaked out. Hopefully, that slightly loose nut was the only problem. But the bike is now ready for me to add the fork oil and go for a ride and see what happens.

-Don- Reno, NV
 
Thanks, I just ordered a couple of quarts of the stuff.
Click to expand...

That ought to do it. You only need about 500cc [16 fl oz] for both tubes.

I think I'd take those down. If the oil has been absent for some time the bumpers (#9) might be shot as well and the valving might be a bit gummed up from being dry (lots of other little bits internally as well). Still, with two quarts of oil to work with you could top them off and see how it rides.

B0000582.png
 
lmo1131 said:
Still, with two quarts of oil to work with you could top them off and see how it rides.
Click to expand...
I changed the fork oil yesterday and rode the bike around 75 miles since then, But it still leaks from the left side with the 13 mm nut now torqued quite tight. But it does seem to be leaking a lot less, perhaps now a half teaspoon in 24 hours or so.

BTW, if I lost all the fork oil in the left side, but had the normal amount on the right side fork, how would the bike ride? What would I notice first?

BTW, the bike felt fine to me in the 75 miles I rode the bike so far since the fork oil change yesterday.

-Don- Reno, NV
 
Well, I wouldn't crank on the bolt anymore! :) Did you use a new washer? Have you tried using something like Hylomar on the underside of the bolt and washer?
 
You shouldn't need anything other than a washer. That said, I'd pull the forks apart and check everything. I'd order #s 8, 9, 10 & 12 for both sides. #9 tends to disintegrate.
 
20774 said:
Well, I wouldn't crank on the bolt anymore! :) Did you use a new washer? Have you tried using something like Hylomar on the underside of the bolt and washer?
Click to expand...
No and no. But I did move the washer and nut to the opposite (right) side. The leak is still on the left side.

But I will try replacing the washer (but the old ones looks fine) and using some Hylomar. Which type of Hylomar would you recommend? I see there are various types.

-Don- Reno, NV
 
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