The gators on my R100 did a good job of hiding the fact that the seals had gone... They can hold a lot of oil!
At first I thought i may have overfilled the forks when i serviced them (not as much oil came out as i put back in) but I'm very sure i pit the correct amount in. Then I saw the seals, which seamed to be uneven.... A Quick prod with my finger revealed them to be very loose, so much so I pulled them out with my fingernail, even tho the stanchions/front wheel etc were still on the bike!
It seems odd that they didn't leak before though.... I didn't use BMW oil, but castrol racing stuff. Could this have shrunk the seals, or am i correct in thinking that the seals had probably had it, and the oil level was too low before to actually get forced out of the duff seals?
Steve1200S wrote:The gators on my R100 did a good job of hiding the fact that the seals had gone... They can hold a lot of oil!
At first I thought i may have overfilled the forks when i serviced them (not as much oil came out as i put back in) but I'm very sure i pit the correct amount in. Then I saw the seals, which seamed to be uneven.... A Quick prod with my finger revealed them to be very loose, so much so I pulled them out with my fingernail, even tho the stanchions/front wheel etc were still on the bike!
It seems odd that they didn't leak before though.... I didn't use BMW oil, but castrol racing stuff. Could this have shrunk the seals, or am i correct in thinking that the seals had probably had it, and the oil level was too low before to actually get forced out of the duff seals?
I used castrol 15 w in mine, but I don't think it was racing stuff. Manufacturer Part Number 17886585
It's been great. I put reconditioned stanchions, progressive springs and new oil seals in, from motorworks.
I can't remember if the fork seals were the type which are rubber coated on the O/D. I'm pretty sure they were. I wonder if a ham fisted previous owner has torn this rubber coating and ruined the interference fit? They need lubricating and pressing in nice and square. Check the chamfer and general condition of the recess in the fork leg. My forks were totally stripped down so nice and clean with zero residual oil, so I went by the recommended quantity rather than height measurement, although I do check with the fork cap removed and the the suspension compressed. Had no issues at all and the upgrade in springs and oil viscosity suits me very well.
I can't imagine that your oil is damaging the seals, but I have been wrong before!
My guess Steve would be a combination of being disturbed, old style seals and the last straw the cold weather causes them to harden and the fork stanchions to contract making the gap larger
--
Steve Parry
Current fleet: '14 F800GS, '87 R80RS, '03 R1100S BoxerCup, '15 R1200RT LE Dynamic, '90 K1, '05 K1200S
Apparently they are meant to be loose and the top cap retains the seal (it clamps to the fork leg with grub screws).... they aren't leak proof though!
New standard BMW seals ordered, and some new brake pads.
(The brakes seem ok, but one pad has some oil on the side of it, so don't want to risk it).
The joys of old bikes.
I was eager to get it fixed, so got up early and stripped the forks this morning before work. All went well, then I jumped on the K and set off (late!) for work..... but the battery was flat!
I can certainly testify for non standard fork seals. I put a set in my R80 and to my chagrin they leaked within a week. Could be that as an interference fit the tolerances have to be spot on.
As for the fork oil, I,d think as long as the quantity is correct and on or close to the correct weight you should be ok. Your bike is a bit special and looks great stock or close to it no need for the gas axe here...... I can almost smell the Solvol from here.
Well the Airhead gurus on the BM Bikes forum told me the oil i used was way too heavy. It was 10w, but seemed very thick to me. Just put in BMW 3w oil in, which is like red water! Should sort it. Plus I've put standard BMW seals in.
Did a load of jobs, rebuilt the front end, cleaned the front brakes and installed some fancy Ferodo pads, put a mud flap on the front, a new rubber for the gear lever, anti-rattle rubbers on the pannier frames and gave it a clean.
Steve1200S wrote:Well the Airhead gurus on the BM Bikes forum told me the oil i used was way too heavy. It was 10w, but seemed very thick to me. Just put in BMW 3w oil in, which is like red water! Should sort it. Plus I've put standard BMW seals in.
Did a load of jobs, rebuilt the front end, cleaned the front brakes and installed some fancy Ferodo pads, put a mud flap on the front, a new rubber for the gear lever, anti-rattle rubbers on the pannier frames and gave it a clean.
Ready for a good nights kip now.
I have to disagree with the guru who said that a higher viscosity will blow the seal. The wrong quantity might, especially if you get hydraulic "lock".
There are probably slight drawbacks with using a grade or two higher viscosity but I'll take that as I much prefer the stiffer feel of 15w in this Beemer of mine. I worked up from 5w to 10w, then settled on 15w. The bike has done 3000 miles with it in and has been pummelled.
The motorworks progressive springs also suit me.
Each to their own.
The jap bikes from the seventies used ATF if I remember rightly? Don't know what viscosity it was, but "red water"" is an apt description.
I think a combination of thick fluid and maybe overfilling slightly blew the old seals, so maybe the 'leak proof' ones are still useable.
They fit like a normal seal, but they are designed to be lose (I'd guess 0.25 of a mm gap around the stanchion and outer edge of the seal).
They aren't as deep as a regular seal, but they need room to float up and down with the pressure.
The top cap (like a hard plastic dust cover) wraps around the fork leg and is held with grub screws. This stops the floating seal floating up to far and out of the fork leg.
From what I can tell, as the seal moves upwards it expands and blocks the fluid from passing....
Steve1200S wrote:I think a combination of thick fluid and maybe overfilling slightly blew the old seals, so maybe the 'leak proof' ones are still useable.
They fit like a normal seal, but they are designed to be lose (I'd guess 0.25 of a mm gap around the stanchion and outer edge of the seal).
They aren't as deep as a regular seal, but they need room to float up and down with the pressure.
The top cap (like a hard plastic dust cover) wraps around the fork leg and is held with grub screws. This stops the floating seal floating up to far and out of the fork leg.
From what I can tell, as the seal moves upwards it expands and blocks the fluid from passing....
The BMW seals are in now anyway, and everything seems fine.
Looking at the sectional drawing of the seal in your attached link, I've come across some pneumatic seals and even hydraulic seals which use a similar shape and need retaining mechanically. They probably do work ok, but the big problem may be that they need a perfect surface on the outside diameter as well as the inner diameter. Unfortunately, on old bikes which may have suffered the odd screwdriver scrape on the outer (housing) diameter, this perfect scenario may not exist. The rubber coated oilseals, which are nowadays commonplace, are fiddly to fit but are perhaps a bit more tolerant of less than perfect housing diameters. Cheap too!
