Have you ever bought a bike, car etc that has been cursed and that you wish you'd never bought, working on them is never easy, and its one problem after another. Costing time, money & pulling your hair out.
My current bête noire is my camper van, I'd just bought a new battery, which I thought had resolved a starting problem,
£97 thank you for a new battery. Problem resolved,
So it was fixed and ready to sell, so I'd listed it on EBAY with a Buy It now price as I'd had enough of all the other niggley & annoying problems.
Sold it on the same day I listed it, but only to some troll with no feedback, who'd no intention of buying it.
Then the starting problem returned and It now appears that its the starter solenoid contacts, which could be a cheap fix or a new starter motor if its the wrong type.
Worst bike I ever had was a BMW R80, never enjoyed owning it. Moto Guzzi Spada was a close second, but it did handle like it was on rails and had a bit of character, and wasn't unreliable, but hadn't been looked after well by the previous owner.
Worst car: VW Golf 1.4 with 4 speed gearbox, under powered, I'd sold my Saab 900 as I thought the GOLF would be cheaper on fuel, which was a huge mistake.
I had more enjoyment from a £50 Talbot Solara compared to the Golf.
So name & shame your worst piece of transport