Hi have bought a new stainless rear mudguard which came with no fixing holes, any tips for fitting?
From my experience don't try drilling the mounting holes you might end up with ragged oval holes. I managed to ruin a metal air box once.
A proper metal hole cutter leaves a neat clean hole
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Put masking tape across the guard and a decent centre punch
I don't find any problem drilling small - up to 3/8" holes - in sheet metal but agree bigger ones can be problematic. I always start with a 1/4" and build up. Those hole punches are good but haven't seen them in smaller sizes.