Sixto,

Look under my name, as I have a post on replacing the tumbler on my 1989 560SEL. Some folks posted some good hints, including what size allen wrench to use to slide into the lock to allow you to unscrew the cap. I did not buy the tool, out of ignorance, and managed with a pair of needle nosed pliers. If you choose to do this, you may want to buy a new cap, as it ends up getting some scratches from the pliers that are visible when you are done. Shooting some WD-40 into the tumbler, to lubricate the threads of the cap would also help. Shoot me an e mail or post any questions you might have, I will tell you what I know. From reading your posts in the past, I am betting this will not be one of your most challenging repairs. It really is not such a hard thing to do.

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1989 560SEL (172k)
1989 325IC (122K)
2004 Suzuki Volusia LE (3500 miles)
2005 Yamaha Road Star (20 K miles)