1999 YZ400f seized, freed up, seized again?

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.

 

First of all maintain maintain maintain u cannot change the oil or clean the airfoil get too much also chain and sprocket wear very severe without lube and keep your bike clean so u can spot problems before they get worse. Now to your issue your bike needs a complete rebuild. With the incidents that occurred I am surprised the rod didn't break. Most lit motor has. Ever been apart so top end. Weds complete rebuild. New valves possibly seats and guides. Piston and can. U need bottom end rebuild those shavings r from your. Rank bearings and cylinder and piston because your. Rank bearings r so worn hence the clunks and the seizing . The smartest thing is buy that engine for 1350 and send it for rebuild

I read your story and the best thing to do is part the bike out. Take money and get a running 400. or a 450 WR or YZ. I see 400s all time 1500-2000 for sale. And take a someone who knows about bikes.

 

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.

 

without a history it'll be hard to diagnose. metal shaving in the oil is a definite start.. i'd pull the engine and start by looking at the simplest and working my way deeper into the engine.. check valves, crank, cam, etc.. also check the tranny, i'm assuming the tranny and engine share oil.

Ditto. I agree completely. And hopefully a lesson learned.

Why would you ride the bike again after an engine seizure? Did you think that the bike repaired itself?

 

Like this?

 

I'm thinking table tennis is the sport for the OP.

yes yes i thought the bike mightve magically repaired itself, or something i did just needed to cool off. however i will start to dig into it now i know what to look for, most likely am going to buy the engine on ebay and either sell the bike, or take damn good care of it because it feels like i just wasted alot of my hard earned money, i appreciate everyone helping me diagnose this, any guesses on why it had 4 gears? or it ran fine again after it seized?

:lol:

first thing you do when you buy a bike, drain at LEAST the oil. I drain all the fluids I can, filters, this that & the other things. Your engine is cooked, metal in the oil is no bueno, oil is the blood of your engine, imagine metal shavings running through your body. that first sieze up was probably your main bearings seizing, after they 'broke' loose and you started it back up is when the destruction most likely started to happen. Theres probably not one good piece left of that engine so your best bet especially with the knowledge you have shown so far is to sell the bike & buy a new one. If you think you can swap it & its worth it to you thats also an option but remember buying a used engine doesnt guarantee the bike will run forever. And if you DO do that, DRAIN the oil first thing! Good luck man! 

 

And ps: my yz450 pulled on everything around here, chances are those 450's you were racing didnt know how to ride. Now I pull 450's on my 250 2 smoker haha! 

What a mess. 

 

In the first place, the YZ400 had a 5 speed transmission, so something is either broken, which could be the source of your trouble, or fishy. 

 

The seize-free up again- seize thing makes suspicious of the rod big end bearing. The roller cages get worn badly enough that they can allow the rollers to skew out of line with the crank pin and lock up like a roller clutch.  You either have a major tear down in your future or a part-out. 

UPDATE: ran the vin, it is a 03 450f, which came with 4 gears from the factory, i pulled the engine from the bike, one intake valve was loose, cam chain did not move, so im still thinking crank seized. no metal shavings came out in the oil, i saw very few at the bottom of the case with a flashlight, i was debating buying a case splitter online, or letting a shop rebuild it, hot rod crank, rod, namura piston, hot rod stage 2 cams, good gaskets, any reason the crank seized? cylinder wall looks good with no scratches, valves are black along with top of piston and spark plug, but looks cleanable, gears still shift, can anyone lead me in the right direction on what to do with it? rebuild? if so what parts? only new crank bearings?

Why don't you have a shop look at it?. Probably just a couple hours of labor to diagnose all the problems, and give you a estimate .

The '03 had a bit of a problem with the big end bearing doing exactly this (seizing/releasing/re-seizing).  The loose valve is likely bent.

Gotcha on the quit guessing comment, those magical dirtbike videos are hilarious, yes the bike is an 03, someone wrote 03yz450 on the frame, along with me double checking the vin number, i was unaware you could split the case without a case splitter so i will look into it

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