2010 Husqvarna 510 smr 6th gear gone

I purchased a 2010 510 smr about a month ago with 4500 miles. Put less then 30 miles on it running around town and heard a loud noise in 6th gear which sounded like chain slap. The noise only occurred when I got on throttle in 6th gear. I thought maybe it was just chain slap since the chain seemed fairly loose. I ended up checking the valves which were all in spec and i also tightened up the chain. I figured i would start on a fresh oil change since i just bought it from a private seller. I ended up dropping the oil and there was a ton of metal shavings attached to the magnetic oil drain plug. I also pulled out part of a gear tooth. Almost all 3 screens and oil filter had metal shavings. I am assuming 6th gear in the trans went but why 6th gear??? I would have thought it would have been a lower gear, unless its a bearing that caused 6th to go.

Either way I have come to terms with it all that I got screwed or I have the worst luck ever. Nothing like getting to know your new bike right off the bat by having to do a full rebuild. Is this something that would have just went or gone over time?? Did i get screwed or have the worst luck ever??

Does any one have experience with 2010 full tear downs? I am going to put a new piston set, bearings, gaskets, and any worn components in the transmission. Should i look to replace anything else? I am going to inspect every part and look for wear. The guy said he has never done anything with the motor besides standard maintenance so is there anything at the 4500 mile mark that i should look to replace??

Any help is greatly appreciated. I will be posting pics of the complete tear down, overhaul, and rebuild.

Thank you, I will make a note to update my default test to black.

while your in there change the shift drum and check your shift forks very carefully, truth is the bike is 5 years old...that's long for high performance motos. may as well re-ring it and depending on hours...rebuild the crank and throw in a new cam chain and sliders. clean up the head and do a valve job.....basically if you splitting cases rebuild it and bullet proof it don't do it half arsed. Sorry for the misfortune oh 6th gear is weakest link on the these bikes.

these are basic twin cam single cyl engines that are very strongly built. I think yours does but if not be sure to install the OEM counterbalance shaft, and I would weld the drive gear onto the crank after being sure its properly aligned and press fitted (use an alignment pin to verify-proper sized drill bit shank)

Well I pulled the engine last night. Here is a look at what came out of the oil.

So should i just change the shift forks and the drum even if there are no signs of wear? Also I was going to stay with all OEM parts, unless there is higher quality after market parts out there. I am going to change the chain and slider but I do not plan on replacing the crank unless it is out of spec.

You probably will not have to replace the shift drum and maybe even the forks, Robert isn't aware that the SM huskys use a steel shift drum not an aluminum like the offroad bikes, this is for durability of course.

Well that's good news, thank you. I will post pics of the forks and drums so you can see what they look like and if they show signs of wear.

Well I'm down to the point of splitting the cases and have yet to buy the case splitting tool. I tried my first attempt at replicating the tool but didn't use a thick enough plate of steel. The case wants to split but I can't get the crank to give way. How difficult or amount of force should it take to split the cases? I double check to make sure everything was free but I can't get it split.