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09 yz 250 knocking noise

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Hey guys

 

Got an interesting problem that the more experienced yz guys might be able to help me out with.

 

 

Basically, whenever I am riding a gear too high/lugging the bike and proceed to roll on the throttle, I get a clearly audible knocking noise which seems to be coming from the left side of the bike.  The noise is not very consistent/rhythmic and the noise only occurs when I'm riding the bike(cant reproduce this when idling or when bike is on a stand).

 

The knocking goes away after the bike builds up some revs.

 

 

Now initially I assumed this was what detonation sounds like, so I mixed 50/50 with vp110 and 93 premium.  No change in the noise.   Then I ran 100% race fuel and got no change with the noise.

 

I next thought this could just be the chain hitting something as I load it when i get on the throttle.

 

I have also thought this could be piston slap.   The issue I have with this theory is I can't reproduce it while idling or on the stand.

Also, I put a new wiseco top end in during the winter.  Specs checked out back then.  Ring end gap was .014", no up and down play in connecting rod, around 1mm side to side...

 

Current piston only has 7 hours on it.

 

 

 

I'm inclined to believe that this is the chain hitting either the swing arm or sub frame and move on with my life. 

 

The issue is I am very paranoid with this kind of stuff and I'm worried it's an engine issue and one day something is going to very,very badly.

 

Any help and/or feedback is greatly appreciated.

 

Thanks  :thumbsup:

 

 

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I love my yzs...but ya they sure are noisy. 

I always wrote it off as slop in the tranny. Never had a problem arise, but i dont like noises either.

The chain does move a ton when you lug around. Agreed.

Id be interested in some other theories.

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I love my yzs...but ya they sure are noisy. 

I always wrote it off as slop in the tranny. Never had a problem arise, but i dont like noises either.

The chain does move a ton when you lug around. Agreed.

Id be interested in some other theories.

 

Have you had a similar noise? 

 

I've searched the web quite a bit and have not been able to find something similar....yet

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I have an 09 also but never had this happen. Maybe I just never noticed it because the bikes are a bit noisy anyway.

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Obviously it's the bike telling you to ride faster!

My 93/97 hybrid makes the same kind of noise (and a ton more grosser sounding ones). Either chain slap or just the shock bouncing against its extended limit when goin over bumps or rocks at a low speed has been my assumption.

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ive been experiencing a similar sound. yz's seem to be noisy bikes. mine makes the same sound its normal . but right now when my bike is in neutral i can hear a rattle coming from the bottom end when the engine is winding down seems to be only in neutral and doesnt start until the bike is warmed up. I just had some bottom end work done too, too fix a much worse sound but atleast it runs im just afraid its gonna break again, originally it was from low gear oil being ran then i got it fixed but now its making that rattle when the engine winds down and also has trouble idling when the choke is pulled out.. wont idle at all actually until its warmed up and choke is normal

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Some interesting replies. And I feel a little better knowing that some of you guys have had similar "issues".

I may have to try tightening the chain and/or put some padding on the swingarm and sub frame and putting around the yard this weekend. Try and isolate the sound.

Hopefully sound goes away, wish me luck!

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Hi all. The noise is deffinatly the clutch plates in the basket. Even when new you will hear it, more the fingers wear the more noise you will hear. My 2010 does same thing. I once had a 89 model and basket was flogged n was so noisey i replaced basket and was still tiny bit noisy but big difference. All good.

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running an engine with low gear oil would not only affect all the gears, clutch, and shift forks,, needing them to be replaced.. anything else does that affect the lower rod bearing also becasue i had a lot of things changed but it still seems noisy like problem isnt fixed

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Hey guys

Got an interesting problem that the more experienced yz guys might be able to help me out with.

Basically, whenever I am riding a gear too high/lugging the bike and proceed to roll on the throttle, I get a clearly audible knocking noise which seems to be coming from the left side of the bike. The noise is not very consistent/rhythmic and the noise only occurs when I'm riding the bike(cant reproduce this when idling or when bike is on a stand).

The knocking goes away after the bike builds up some revs.

Now initially I assumed this was what detonation sounds like, so I mixed 50/50 with vp110 and 93 premium. No change in the noise. Then I ran 100% race fuel and got no change with the noise.

I next thought this could just be the chain hitting something as I load it when i get on the throttle.

I have also thought this could be piston slap. The issue I have with this theory is I can't reproduce it while idling or on the stand.

Also, I put a new wiseco top end in during the winter. Specs checked out back then. Ring end gap was .014", no up and down play in connecting rod, around 1mm side to side...

Current piston only has 7 hours on it.

I'm inclined to believe that this is the chain hitting either the swing arm or sub frame and move on with my life.

The issue is I am very paranoid with this kind of stuff and I'm worried it's an engine issue and one day something is going to very,very badly.

Any help and/or feedback is greatly appreciated.

Thanks :thumbsup:

every 2 stroke does that lol

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every 2 stroke does that lol

In fairness, this is my first smoker haha.

Also, I'd be surprised if it was the lower rod bearing. Play was well within specs when I took it apart 7-8 hours ago.

No guarantees though, I've been wrong before.

Edited by chris88

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Mine rattles. Scared the hell out of me thinking it was something big. I noticed if i pull in the clutch lever while its running the rattle changes. Lever out its louder, lever in its muted but still there. If everything is in spec just ride. Hell, if it isnt in spec and youre broke ride anyway ;). Ive learned the only way to know the bike is perfect is to never ride it. These are supposed to be fun! (This is coming from a pessimist, btw)

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Try a new chain and sprockets. Old ones don't just slap. They generate back lash when lugged under load which then whip cracks the chain and also sends a nasty back lash through the transmission and clutch. In my opinion, a sound like that means accelerated wear. My 2004 original bottom end does nothing like that and it's done considerable work.

Next time you fit a new swingarm slider, put an even bed of silicone sealant under it. That dampens chain forces a lot.

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Figured I'd give this thread a little update.

 

Raced today, re-tightened my chain before and the noise was much lees frequent and audible.  I might have just left it a little too loose before  :bonk:

 

Also, I noticed about 25%-33% of the other yz250's cruising around were giving off the same noise.  Many other bikes were doing it as well.  

 

So now I can rest easy tonight.   Ordered a x ring chain with 14 49 sprockets for wednesday.

:ride:

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Bingo. There you go.

 

Tighter chain reduces the problem and noise. But an over tight chain is not the fix. The real fix is a decent chain, as you've ordered already, and new sprockets to go with it.

 

The problem is usually worse when just cruising. Under steady one direction load you don't get the chain whip or chain+transmission back-lash effect.

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