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Yz250 high pitched engine screech

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I just got a 07 Yz250 a month ago, I have this awful noise now and thought maybe someone has some info they could share on here. Did a top end and replaced the water pump seals and bearings before I rode it. Rode it a like 3-4 times so far, oil change after each ride, with shell rotella. They oil comes out grey even after less then an hour of riding, not milky though a dark grey. Last ride the sound started, it's a high pitched, whirling, screeching sound that cuts in and out, on and off. Idle, in gear, clutch pulled in nothing seems to affect it. I tried cold starting it a couple days after discovering this to hear the sound again and it took a lot of kickin and time to start which is new. I can only think crankshaft bearings which is just a nightmare for me. Does anyone agree or have alternative possibilities? I ll be going in soon but any info beforehand would be great.

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Had this happen on my KX250 after it went for a little dip in some water. I flushed everything I could possibly do before I ran it again. Ended up being the crankshaft bearings. It eventually seized right up after letting it sit for a week while I was at work.

Replaced my whole bottom end/top end, then some chump stole it with a half hour of run time.

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Had this happen on my KX250 after it went for a little dip in some water. I flushed everything I could possibly do before I ran it again. Ended up being the crankshaft bearings. It eventually seized right up after letting it sit for a week while I was at work.

Replaced my whole bottom end/top end, then some chump stole it with a half hour of run time.

Yea that would be terrible. I would be happy if someone stole it right now I could cut my losses and get like half the money I have into it back through insurance, and say **** this and buy a brand new yz250. I just hope they still make new yz250s when I buy my next bike cause I don't want to go through this again

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Yea that would be terrible. I would be happy if someone stole it right now I could cut my losses and get like half the money I have into it back through insurance, and say **** this and buy a brand new yz250. I just hope they still make new yz250s when I buy my next bike cause I don't want to go through this again

Are you doing the work yourself?

There's only small updates from 06 and up. I couldn't see myself paying 7500$ for a new one. I grabbed a newish 11 for 5K with tons of extras. (Canada)

You could get a whole Wiseco rebuild kit bottom and top off eBay for about 330$ I think.

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Are you doing the work yourself?

There's only small updates from 06 and up. I couldn't see myself paying 7500$ for a new one. I grabbed a newish 11 for 5K with tons of extras. (Canada)

You could get a whole Wiseco rebuild kit bottom and top off eBay for about 330$ I think.

I appreciate the advice man, I've always been against buying new but now I've realized updates or not buying new is about avoiding the retard previous owners who just absolutely mangle what should be a reliable bike with a long life ahead of it. In the end after this and all the other work I'm going to have to put in ( cylinder is damaged will need to be replace eventually, clutch worn ect) I ll be just shy of the cost of a new bike and still some parts not perfect. And as for the weisco, I didn't just put like 5500 and counting into a bike with a Chinese part at the heart of it. I ll rebuild my oem crank if necessary and just get oem bearings and seals, probly keep my piston just replace clips it's got like 5 hours

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I appreciate the advice man, I've always been against buying new but now I've realized updates or not buying new is about avoiding the retard previous owners who just absolutely mangle what should be a reliable bike with a long life ahead of it. In the end after this and all the other work I'm going to have to put in ( cylinder is damaged will need to be replace eventually, clutch worn ect) I ll be just shy of the cost of a new bike and still some parts not perfect. And as for the weisco, I didn't just put like 5500 and counting into a bike with a Chinese part at the heart of it. I ll rebuild my oem crank if necessary and just get oem bearings and seals, probly keep my piston just replace clips it's got like 5 hours

Yeah. I only buy used when I know the previous owner. In this case, I did.

Can't go wrong with OEM. Everyone has their own opinion on Wiseco, I've had great luck with them In the past. I am about to throw a piston in my bike very soon.

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Drain trans oil and refill with 750 cc of fresh oil measured from a 1 quart bottle or measuring jug. The level check screw is too low in the cases. YZ250s don't sound nice when they have very little trans oil. Clutch input shaft bushings is typically under-lubricated when too little trans oil and if you or the PO ran the bike hard with less than 750cc, it can gall/fail/melt.

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- Try to identify what area the screeching is coming from (front or back of engine). You can put the metal end of a screwdriver on the case, and the handle up to your ear. Looks ridiculous, but it works :)

- Does the screeching change it's pitch when you shift gears?

When you dump your oil, run it through a pantyhose, see if any shiny metallic pieces are left behind (even better if you have a magneitc drain plug, but some are non-magnetic, so use both methods).

Sucks...

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Drain trans oil and refill with 750 cc of fresh oil measured from a 1 quart bottle or measuring jug. The level check screw is too low in the cases. YZ250s don't sound nice when they have very little trans oil. Clutch input shaft bushings is typically under-lubricated when too little trans oil and if you or the PO ran the bike hard with less than 750cc, it can gall/fail/melt.

Should have mentioned that was the first thing I checked, even though I always measure out anyway but just to be sure. But where is the clutch input shaft bushing I should check that before I split the cases

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When you dump your oil, run it through a pantyhose,

+1 this will help you differentiate if you've got steel or brass if debris (whereas a magnetic drain plug only grabs steel).

Friend seized his yz250 trans on the clutch input shaft after running in dunes with too little trans oil.

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- Try to identify what area the screeching is coming from (front or back of engine). You can put the metal end of a screwdriver on the case, and the handle up to your ear. Looks ridiculous, but it works :)

- Does the screeching change it's pitch when you shift gears?

When you dump your oil, run it through a pantyhose, see if any shiny metallic pieces are left behind (even better if you have a magneitc drain plug, but some are non-magnetic, so use both methods).

Sucks...

Good tip with the screw driver I ll try that, as for the oil it's mixed it's been drained and disposed and I don't want to run the bike anymore before this issue is addressed, but I think I should see anything that has been damaged when I remove the side cover and split the cases. And no the noise continues exactly the same in idle, any gear and whatever position the clutch is in all though it comes and goes but seemingly completely at random. To me it seems like that's gotta be crank

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I had a pretty bad squeal when a tranny gear went out...does the squeal stop in any particular gear? Either way she needs to come apart

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If it's squeeling with the clutch pulled in or let out then it has to be engine related, not trans... Pull apart your top and bottom end, check each and every bearing and find the culprit. Spend the money and you'll be glad you did. You will have a solid running bike after the effort. And replace every seal in that thing... Including Crank seals

Edited by steveblymyer

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