Stretched the oil change interval on my KTM 450 EXC-R.
That blew up the connecting rod bearing, necessitating replacement of most of the engine internals. Cost a few K.
Dropped my FJR1300 in the driveway
$460 in parts and a Saturday afternoon that I’ll never get back
My most expensive screw-up?
That's easy....I married my (now ex) wife.
Is that because they've learned not to loan stuff to you? :laughingTaking out a friends Polaris 800 4 wheeler with 100 miles on it and doing a 5 roll yard sale on it. Drive it like you stole it.
Drove it back on 3 operating wheels, 1 dragging and no bodywork left. Pretty much a write off.
Really expensive. Good lesson though. I have never borrowed anything from anyone before or after.