Took my K100 up for its mot today and it passed....   So out for a run and I'm impressed with the way it goes. Did about 50 miles and when I got home noticed that the fork seals were leaking, the left worse than the right.

Now what's strange is that I did them yesterday and using BMW originals that came as part of a spares cache. At point of fitting they were fine and were also fine on the ride to the MOT centre about 4 miles away.

I've successfully fitted fork seals to numerous machines and never had any leak. used the time honoured method of bashing them in using the old seal on top of the new and a suitably sized socket as a driver. I also sanded the end of the stanchion with 1200 wet and dry applied some red grease and carefully inserted the stanchion into the new seal.

My thoughts.

The seals were old stock and not in a bag, dried out shrunk?? (they looked and felt okay)

I used 10W oil to provide a firmer feel to the front end but its too heavy for the seal?

Accept the fact I've not fitted them properly.

Anyone care to jump in?

Are the stanchions scratched/scored? The Sachs forks like to do this, mine has a pair of gaiters fitted with good clips at both ends to hold the oil in for totally unrelated reasons 

Sorted, found a pair of the cheap pyramid ones in the 'spares box' decided to fit the stanchions into the sliders first then ease the seal over the top of the stanchion and belt it into place with a length of 40mm waste pipe split down the middle to fit over the stanchion. I also used the end of a 40mm coupler between the pipe and the seal as it's thicker than the pipe and exerts a more even pressure on the fork seal. No more leaks.

Cheers SB, your reply came up as I was typing this one, oil filled gaitors 'pon my soul, whatever next  

If the MOT man passes it because he can't remove the gaiters to have a look then it's fair game!  

Surprised by Pyramid seals working better than OE but nice to know. I don't suppose you paid particular attention to those seals perchance, like whether they are single or double lipped or who actually made them?

They were double lipped but I didn't look for a makers name. They were also a far easier fit into the slider than the BMW items. 

I know they get mixed reviews but I've used pyramid seals before without any problems.