The frame's anodised, and any caustic liquid or sandpaper will destroy the finish... unless it's already been stripped and polished in a previous life. Even then it's possible (although unlikely) that it's been clear coated.

The best thing is to completely strip it and have it vapour blasted, but that's rather extreme, and most people won't want to go to that level, so you're really left with careful hand cleaning with gentle solvents and a toothbrush! (Use automotive approved products suitable for alloys.) Brake cleaner or degreasers such as Gunk or Jizer can get the majority of the grime off, or you can even use TYGA's "soup" (although it's not particularly environmentally friendly!), but the worst of the stains will remain without a deep clean by vapour blasting.
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Andy.
NSR-WORLD.COM

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