1 Ever wondered what's inside a BMW damper? Thu Mar 06, 2014 5:04 pm
sidecar paul
Life time member
Not a lot, actually.
Had it not said "DO NOT OPEN" and "NICHT ÖFFNEN" I probably wouldn't have bothered, but, as I had a knackered damper, well............
I first milled a bit off the side of the top cap to see if there was evidence of a thread.....nothing. So then I milled two flats on the top cap to be able to grip it in the vice. With some heat and a lot of leverage the top cap moved and came off. It appears to be a pressed fit with some sort of glue.
Once that was out of the way, I was greeted with another "DO NOT OPEN" "NICHT ÖFFNEN" on the top seal holder. This required some pressure to squash the seal that's situated below the holder so that I could release the spring circlip; a bit tricky, but by putting the body in the lathe chuck and using a tubular spacer over the damper rod, I was able to apply enough pressure from the tail stock. Once the circlip is out of the way, the bump stop (that red thing) gives enough free play to push out the seal holder.
Another wire circlip which locates the lower seal holder comes out easily which then allows the piston assembly to be withdrawn.
One point worth mentioning is that, as there is no separate 'air pocket' to compensate for the damper rod volume, the damper will only work properly when it's fitted the right way up; ie, with the alloy fitting at the bottom.
So, what now: maybe I'll make a new damper rod (the old one is worn through the plating) and re-assemble it just for the fun of it. Can't imagine using it though, there are better dampers around.
I liked getting past BMW's instructions though, why shouldn't it be opened?
Paul.
Had it not said "DO NOT OPEN" and "NICHT ÖFFNEN" I probably wouldn't have bothered, but, as I had a knackered damper, well............
I first milled a bit off the side of the top cap to see if there was evidence of a thread.....nothing. So then I milled two flats on the top cap to be able to grip it in the vice. With some heat and a lot of leverage the top cap moved and came off. It appears to be a pressed fit with some sort of glue.
Once that was out of the way, I was greeted with another "DO NOT OPEN" "NICHT ÖFFNEN" on the top seal holder. This required some pressure to squash the seal that's situated below the holder so that I could release the spring circlip; a bit tricky, but by putting the body in the lathe chuck and using a tubular spacer over the damper rod, I was able to apply enough pressure from the tail stock. Once the circlip is out of the way, the bump stop (that red thing) gives enough free play to push out the seal holder.
Another wire circlip which locates the lower seal holder comes out easily which then allows the piston assembly to be withdrawn.
One point worth mentioning is that, as there is no separate 'air pocket' to compensate for the damper rod volume, the damper will only work properly when it's fitted the right way up; ie, with the alloy fitting at the bottom.
So, what now: maybe I'll make a new damper rod (the old one is worn through the plating) and re-assemble it just for the fun of it. Can't imagine using it though, there are better dampers around.
I liked getting past BMW's instructions though, why shouldn't it be opened?
Paul.
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'84 K100RS (0014643) (owned since '85), 86 K100RS (0018891) with Martello sidecar (built as an outfit in '88),
'51 Vincent (since '67),'72 Montesa Cota (from new), '87 Honda RS125R NF4 (bought 2015)
....No CARS never ever!