Okay, so i bought a 1999 yz400f without knowing what it was for one, because the owner told me it was 250f, it was a very solid bike, good compression, strong bottom end, only had 4 gears? dont know why but i didnt question it, ran perfect(only small flaw was the exhaust clamp wasnt on, so between the header andmuffler it pushed black exhaust out of the jug and leaked but i didnt think anything of it because it ran good), never even got to making my first oil change on it which i regret doing as soon as i got it, i rode this bad boy around for about 2-4 weeks straight everyday (yes yes i know dumb idea without maintenance) but i was in love, it beat everyone elses 450f's, and was the baddest bike of them all, truly was the thump heard around the world. However, my love for this bike is not what we the people are here to discuss, i was riding one day to my friends house,(15 and this is how i commute), and all of a sudden i lose power and my rear tire locks up, i roll to the nearest gas station on the side of the road, and attempt to kick it over again not knowing what the heck just happened. kicks over 3 or 4 times then locked up completely. so i had my buddy bring it back to my house in the back of his truck, i let it sit around in my shed for a week due to me pricing out parts for this 400f(dont get mad, was my first dirtbike that i bought so i didnt know how to tell what was what), i guess i was blessed and bought a very healthy very rare bike, the 1999 YZ400F. thats right, not the problem-filled 1998 version, the stronger more improved 1999! i go look at the bike a week later and am playing with the kick starter, and it freely moves again, i was shocked, i was filled with joy and could not believe my eyes, i hopped on it and attempted to kick it over about 125-150 times before it finally started, i rode it up and down my street(it had all the power it did before it seized) and rode good for about an hour, i rode over to my friends house again to show them so i could prove i wasnt dreaming, but then the second time i started it, rode it out of my friends driveway, i heard a big *clunk* coming from the back lower end of my engine, i continued to drive thinking it was a rock or something hitting my frame or another piece of metal on my bike, and i was already late to get home, and next thing you know i pull in the clutch, lose power, and it seized up again, i waited another 30 minutes of walking this heavy monstrosity down the trail towards my house, and it kicks over again! what the heck right? i got it to start once more, then it did the same thing, i gave up and got home and put it in the shed to hopefully never look at it again, i was so frustrated, i now moved into a new house so it had some time to sit, still locked up, i looked in the oil fill and there is metal shavings, 2 months later it still will not kick over, i drained the oil and saw how clogged the filter was, along with the air filter, mind you this was my first ever time doing any sort of maintenance to the yz, i dont want to go ripping out the engine without anything to look for, i cant not find anyone with the same problem for my bike, and hard to find rebuild kits, seems like my only options are buying a whole new engine ($1350 on ebay) or buying a whole bottom end ($400-600) on ebay for the bike and swapping the damaged parts, i need outside knowledge if anyone has had this happen to them or can lead me in the right direction on to what happened.