Thanks in advance for any help. Also, sorry but this may be lengthy. Me and a buddy rebuilt a 2006 honda foreman trx500. We started this adventure because of it smoking. We tore it down and noticed that the person who bored it out a few weeks prior had completely screwed it up. The piston wasn't even close to fitting (too small) and the cylinder looked like a football. I don't even know how it had enough compression to run. Anyhow, we ordered all new parts (cylinder, piston, wrist pin, ...). We reassembled it and heard some bottom end knocking. So we tore it back down, this time to the crankshaft, and measured the clearances for the connecting rod, which as you can guess was also screwed up. So we replaced the crankshaft and reassembled it. This time the motor sounds like a champ and no smoke. But when we test drive it second gear just clatters and shakes the atv a little but it will not go. Bear in mind that only second gear clatters not any of the others and it did not do this prior to the rebuild. We wondered why the transmission was messed up since we did not touch it. So we tore it down again. This time I tore down the entire transmission and reassembled it piece by piece and followed every word in the book. I found where a thrust washer was missing (maybe it fell off druing installation of the crankshaft). Just today I reassembled it (with the thrust washer) and for the first few passes of running through the gears (1 through 5) it runs perfectly, without getting on the gas hard. After the first few passes second gears starts to clatter again and will not move the atv. I continued to run the atv in idle and just driving in the other gears for 30 minutes or so and then I changed the oil. Weird enough, after the oil change second gear clatters about 2 times and ten jumps into first gear. This is the state it is currently in. Please help, anyone. I need to get second gear back. Thanks. Andrew

 

So I rode it a little more today. When I try to put it in second the atv kind of jumps forward as if the gears are catching a little but slips. When I first try to go to third When I go through second it jumps to first, then I can run through second again and it lets me go to third. Please keep in mind none of the occurred before the rebuild, so I'm told by my friend, the owner. When I tore it down I did not see any bent forks and the gears looked brand new. It only has about 160 miles on it. Thanks for any help.