Decided to freshen up the top end on my bike with a rebore, piston kit and some new valves. By saturday lunch time I had the bulk of it back together just needed to setup the timing and valve clearances then put everything back but I had left my 8mm allen key for the 'T' mark cover and my feeler gauges at work. I wanted to avoid going to work at all costs as I wasn't on call out duty that weekend but if I went in I'd probably end up getting pulled onto a job, so I went to town to buy some feelers and allen keys. Nowhere had any so I had no choice but to try to sneak in and out of work. Ended up spending 6 hours overhauling a centrifugal separator... Got home too late to work on the bike.. So I got up nice and early today to finally get it boxed off, eager to hear her fire up again. I was just putting the cam sprocket back on to the cam shaft once lined up correctly when the little key pin decided not to be fixed anymore and drop down the timing chain hole! ARRRRRGGGHH @#!? I got a torch out and was able to see it just resting on top of the primary cam gear, if i can see it I can reach it right? No need to pull the cylinder etc off again - maybe I'll get it finished today after all. Nope, I didn't have any pickup tools with me so I went to the only place near on a sunday which might sell them, maplin. They had a few to choose from but unfortunately the only one in stock was a magnetic one with a bigger magnet than I wanted. I tried it anyway and it just about fit, but the magnet was so strong that before reaching the keyway pin it grabbed the cam chain, which nudged the key pin off the sprocket it was sat on causing it to fall out of site right to the bottom of the engine. So now, I'm worse than back where I started as I'll have to order a clutch cover gasket as I'll be removing that now - then starting from scratch. I miss my old job purely for the fact I had use of the workshop at weekends, way more tools and didn't have to work outside on a driveway with whatever kit I can fetch home in a rucksack. Is there a chance this pin could've come loose after the rebuild, when running and actually done some substantial damage to the engine? - Knowing that would make me feel better..