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Post Info TOPIC: High pitched engine noise, louder when hot


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High pitched engine noise, louder when hot
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Hi Guys,

My 2005 TTR250 has a high pitched noise that gets louder with RPMs and when the engine gets hot. Clutch in or out makes no difference and neither does bike speed. I've only noticed it the last few hundred miles and it's been getting louder. Sometimes the engine makes a hard clunk when it shuts off and I learned here that it is the sprag clutch. Bike has been doing that for years though. Do bad sprag clutches howl too?

The noise:

Things I've tried:

1. Slacking the timing chain by unscrewing the timing chain tensioner screw while engine running. No change, just some chain rattle noise when slackened like I would expect.

2. Listening with a mechanic's stethoscope to find where it's loudest. The only place I could hear any high pitched noises was on the timing chain tensioner but it didn't sound the same pitch, was higher. To my ear it sounds loudest at the rear of the transmission but nothing in there is spinning when in gear and clutch pulled, but still makes the same noise.

Any ideas?



-- Edited by alexkram on Tuesday 9th of January 2024 11:35:33 PM

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Hi i recently had to replace my sprag, in my case it had the bang but didn't make a noise when running. can't think of what could be causing the noise, thinking about it the info of clutch in , limits the moving parts to crank/flywheel, piston. cam /cam chain clutch basket, oil pump and balancer shaft.  

so your question about the sprag is a good one, maybe you could try running it without the small gear under the left-hand cover (engages with the starter) if the noise stops i could be the sprag .I'd wait for other replies first though. (mine has the kick start as well so can still be started)



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Ttboof wrote:

maybe you could try running it without the small gear under the left-hand cover (engages with the starter) if the noise stops i could be the sprag .


 This is a smart suggestion. I don't have a kick starter but I could push start it.



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I ran it without starter gears and it's the same so the starter sprag is not it. Thanks for the suggestion.

Funny thing is I listened again and it sounds like it's coming from the muffler area. Not out the tail pipe but from where the exhaust pipe meets the muffler. Muffler bearings going bad? If that is the case I'm no longer worried about the engine locking up but still annoying to ride like that.



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i can't hear the noise very well on the clip, if the seal/gasket is leaking you might be able to see some black marks where its leaking, also when cold hitting the pipe with your hand you might notice the pipe is loose where it fits into the muffler. the gasket is pretty cheap from Yamaha if it's the culprit. I think i have one in the shed but I'm on the other side of the world and I'm holding onto it Just in case i fit the original muffler back on.

 

just a suggestion, with the sprag dont wait too long like i did its  easy and a lot cheaper to replace the sprag before it damages other parts, i got mine through partzilla ( i had to replace a sprag and a starter)



-- Edited by Ttboof on Wednesday 10th of January 2024 02:05:48 AM

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The OEM sprag from Partzilla is $150 while the generic ones on ebay are $52. Is the OEM one the way to go?



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if you Search the forum , you will see many people have had no luck with the non-genuine sprags , the OEM is the way to go in my opinion  



-- Edited by Ttboof on Wednesday 10th of January 2024 02:03:42 AM



-- Edited by Ttboof on Wednesday 10th of January 2024 02:04:36 AM

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As is so often the case. Thanks for the tips, will order it now.



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i don't know how partzilla sells them at that price. there about 4 times that here in Australia. Brian has a great how to fit a sprag thread on here .  Tip if you don't have a bolt to take the fly wheel off the back axel bolt works well, i took the axel bolt to the local bolt shop and bought a bolt with the same thread and use that.

 



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Sounds like resonance through the exhaust and should not be an issue.  I don't like to run an air-cooled engine at high rpm while parked because you will overheat it.  You should keep an eye on the exhaust pipe header and back the throttle as it begins to glow red.   I would be more concerned about valve train clacking or engine knocking noises.  Your engine sounds fine.  But pay close attention to the sprag and replace it before it causes any damage.  I've had good luck with sprag kits from Taiwan.  They are currently around $120 on ebay.  The good thing with these sprag kits is that they include the sprag clutch gear and gear bearing.  Avoid any sprags and sprag kits on ebay under $100 as these are the faulty Chinese sprags that failed for alot of members.



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Jeff B wrote:

Sounds like resonance through the exhaust and should not be an issue.  I don't like to run an air-cooled engine at high rpm while parked because you will overheat it.  You should keep an eye on the exhaust pipe header and back the throttle as it begins to glow red.   I would be more concerned about valve train clacking or engine knocking noises.  Your engine sounds fine.  But pay close attention to the sprag and replace it before it causes any damage.  I've had good luck with sprag kits from Taiwan.  They are currently around $120 on ebay.  The good thing with these sprag kits is that they include the sprag clutch gear and gear bearing.  Avoid any sprags and sprag kits on ebay under $100 as these are the faulty Chinese sprags that failed for alot of members.

 

Thanks for the tips. OEM sprag, FW puller, and gasket ordered. I have done many similar repairs before, shouldn't be an issue. I am no longer concerned about the howling noise but I still think it's strange.

I have a temperature sensor on the head, displayed on my Trailtech speedometer. I stopped when it got to 275F 



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I replaced the sprag clutch today. Could have gone better. Oil drain bolt head stripped out, was too tight (I'm the only one to blame for that). The new sprag clutch slipped out of the housing when I picked it up and landed right into my metals recycling bin. I didn't notice until later that one of the wedges had fallen out. It was hiding in the bin with hundreds of old bearing balls, races, filings, and other metal debris. So I had to remove the new sprag from the flywheel again to reinstall that. I accidentally ordered the right side gasket instead of the left side so I used silicone gasket maker instead. The old gasket was separating so it had to be scraped off. Oh what a difficult chore that was! Scraping the old gasket from the stator cover took over an hour. Hopefully the lack of a gasket won't cause any problems with clearances.

Edited to add: The starter gear has noticeable wear on it that I can feel with my fingernail. I'm glad I replaced the sprag now as opposed to when the bike won't start and it's much more expensive.



-- Edited by alexkram on Wednesday 24th of January 2024 02:11:36 AM

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sounds like one of those if it can go wrong it will jobs but sounds like you got there in the end. 

its good you changed the sprag before it caused more problems . 

Im still not impressed i waited too long and it took the splines off the starter armature  as well 



-- Edited by Ttboof on Wednesday 24th of January 2024 04:10:35 AM

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