While making the carb jetting tutorial featured at this link horrible disaster struck. While removing the top plate of my carb, i dropped one of the allen head screws. In an effort to push forward, I decided to find it later during re-assembly, and continue taking pics for the jetting tutorial. After i was done with the pics, i i looked around the nooks and crannines of the bike...not finding it. I humped the bike off the stand, and rolled it forward to get it out of the work area...so i could look around the garage floor. Unknowingly, the bike was in gear...i pushed forward, hearing the engine turn over, then lock..my rear tire skidded to a stop... and it dawned on me. I KNOW WHERE I DROPPED THE SCREW!!! I immediately roll the bike back, unhook my subframe, and using a magnet retriever, fish my screw from the intake port of the engine, middle valve. DAMMIT DAMMIT DAMMIT!!! the threads of the screw are buggered up BAD...meaning it got pinched in the valve, and did God knows how much damage. Fast forward 12 hours to friend and fellow dental student, and TT member Just034's garage. He has never taken off a head, but he HAS done a valve job before, so that means that his expertise far outweighs mine. we drain all the fluids and start dissasembling.... find TDC and we mark our chain. http://www.planetblade.com/arins/bike/disaster/a.jpg Hey, my spark plug looks pretty good at least! http://www.planetblade.com/arins/bike/disaster/b.jpg we get the head off and my worst fears are realized. The valve seat is dinged up...and so is the top of the piston head. http://www.planetblade.com/arins/bike/disaster/c.jpg http://www.planetblade.com/arins/bike/disaster/d.jpg http://www.planetblade.com/arins/bike/disaster/e.jpg the valve wont hold acetone that is poured in the intake side...it doesnt seal. We make a valve compressing tool from a deep socket with a window cut out, and a large C clamp. This allows us to remove the valve retaining wedges, and remove the valve. http://www.planetblade.com/arins/bike/disaster/l.jpg This valve is bent badly. http://www.planetblade.com/arins/bike/disaster/g.jpg And the valve seating surface is buggered up good, notice the galling right at the seating surface. http://www.planetblade.com/arins/bike/disaster/f.jpg http://www.planetblade.com/arins/bike/disaster/h.jpg SO, its off to yamaha store to get new valve, and autoparts store to get valve grinding compound. Mind you, this is further than either of us has ever been into an engine. Im scared, Just034 is excited (he's crazy). Seating the new valve in the head doesnt pass the acetone test either, it leaks, the seating surface of the head needs to be refinished. We use a cordless drill, with a piece of vent tubing chucked into it...we seat the valve, slide the tubing over the valve stem, so we can spin the valve against the seating surface of the head...we add grinding compound, and spin it...applying moderate force to the spinning valve. After that, we finish up with some red rouge, mixed with grease, to put a nice finish on the seating surfaces. and i dremmel out the big gouges in the aluminum head. not so shabby anymore eh? http://www.planetblade.com/arins/bike/disaster/i.jpg We reseat the piston, and it passes the acetone test...it seals. thank God. http://www.planetblade.com/arins/bike/disaster/j.jpg I grind the burrs off of the piston head. and we reshim my valves the poor-man's way....with a diamond hone and a digital caliper...shaving the shims down until they are within the specs i need. http://www.planetblade.com/arins/bike/disaster/m.jpg We button up the engine, i take the bike back home and finish assembly, and it fires right up, exactly 24 hours from the time i lost the screw... and whats even better, my new jetting feels good too! thanks for watching.