My tank cap is badly corroded, likely due to the hydrophilic properties of ethanol, so I took it off to clean. The rubber seal was also cracking badly, so it's only a matter of time before I'll have to replace it. Anyhow, I took it all apart and noticed that the lock barrel was also corroding badly, which was a worry. While messing around cleaning the lock and making sure all the were tumblers free, I got distracted by a few women chatting with me and I lost my mental map of things (in future I'm going to shoo them away). Long story short, after I assembled it all and tried it, it wouldn't open. I messed around for ages trying, to no avail. Left it overnight and tried again this morning and managed to pry the cap off by taking out the cap bolts and moving it 45 degree to 9 O clock and tugging it off. So now I've taken out all the tumblers so the cap will pop by inserting anything that'll fit. No more worries about bending keys or being locked out in future.