I got my Speedmaster last year in November and she is a 2010 model I only put about 1800kms on it and I now have this problem on the top triple tree.
The bike goes into the shop on Monday to get some photos taken of it and then sent off to Triumph to see about a warranty claim, what I know about it is that Triumph apply a clear plastic flim to the top triple tree and risers the same to what Harley do to there bikes and somehow moisture gets trapped under this flim and starts this worming affect that we see and the shop told me remove the clear flim and you will have no more trouble with the worming cheers.
