YZ250 Rattling Sound When Revving Out?

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9/12/2018 6:36 AM

Posting for a friend since he does not have an account.

His problem is his yz250 has a slight rattle sound almost like metal tapping metal sound when he revs the bike out. He had a shop check the motor out and they said it looked amazing inside. He is riding at a real high elevation. Could it be the bike is too lean? Also me and him both have heard yz’s have a lot of clutch chatter or chatter in general. Could it be the powervalve? His does leak a bit (grime on the outside cases)

Any direction to go in? We both tried doing some research and couldnt put a finger on it...

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9/12/2018 7:15 AM

What i would do is go over to harbor freight and buy a mechanics stethoscope and use it to pin point where that rattle is coming from. I think theyre like $3. Once you localize it it will be easy to fix.

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9/12/2018 4:43 PM

Noises can be hard to track down... I know as I have been chasing one on my truck for a while. Anywho, a decent and easy place to start is the chassis. Make sure everything is torqued properly, even something as simple as a loose spring in the kickstart retainer, or a loose mount for the motor or a skid plate can make noise that sounds like its coming from the motor. If it indeed is coming from the motor, the stethoscope option from above is good, or maybe a tear down this fall for a refresh and once over is good. Not sure of the year or hours, but while these are solid machines, they do require some TLC to keep running fresh.

Also if you can post a video clip, might be easier for us keyboard warriors to diagnose.

Good Luck

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9/12/2018 7:44 PM
Edited Date/Time: 9/12/2018 7:45 PM

nch209 wrote:

Noises can be hard to track down... I know as I have been chasing one on my truck for a while. Anywho, a decent and easy place to start is the chassis. Make sure everything is torqued properly, even something as simple as a loose spring in the kickstart retainer, or a loose mount for the motor or a skid plate can make noise that sounds like its coming from the motor. If it indeed is coming from the motor, the stethoscope option from above is good, or maybe a tear down this fall for a refresh and once over is good. Not sure of the year or hours, but while these are solid machines, they do require some TLC to keep running fresh.

Also if you can post a video clip, might be easier for us keyboard warriors to diagnose.

Good Luck

Actually thinking it may be the plastic skidplate or even the kickstart lever since you brought them up. He cranked the bike up and it sounded real stout and strong. No noises.

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9/13/2018 2:40 AM

I had a bad rattle noise on my bike a few times. Turned out to be the shock spring being loose

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9/13/2018 5:29 AM

all my yz's have had the kick starter rattle after some time.

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9/16/2018 4:43 AM

Exhaust pipe springs? Old exhaust o-ring?

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9/17/2018 11:25 AM

What year is it? Is he running pump gas? YZ250s detonate on pump gas, and that could be the sound being heard.

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