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Discussion Starter #1
Hi guys,

First day, first post. So hi to all. I'm hoping y'all can help me with a clutch/transmission issue. I originally thought it was a chain/sprocket issue but increasingly sure that the noise was coming from the engine I took front sprocket and chain off yesterday to run the engine and shaft to see if it made a noise itself. Please see link below for a vid of the countershaft running. If any of you have any idea what it may be, any advice ould be much much appreciated. Other than the sound making me go bonkers with trying to figure out what it is, I'm planning to do a tour of the south-east in a couple of weeks and of course only want to go if it's deemed safe enough to run the distance. Thanks in advance for any viewpoints.

https://www.youtube.com/watch?v=d-UFKjoPiAE



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Did this just recently appear? How fresh is the oil and is it at the proper level? Have there been any changes made to the motorcycle recently?
 

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Discussion Starter #4
It's been noticeable since early summer. Oil is fine, up to the level and changed with last service, about two months ago. Most recent change has been a new slip-on, Micron exhaust.
 

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What year model and what model designation is this machine?
I can look up it's internal parts if I know what it is.
Does the noise go away completely when the clutch lever is pulled in?
 

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As much as I can tell from the video, it sounds very similar to primary chain rattle. Especially how it changes with the clutch in. My old Goldwings do exactly that if the carbs end up out of sync. It could be a lot and sounds are hard to diagnose via the net, but that's a possibility.
 

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Discussion Starter #7
It's a CB600F-Y Hornet from 2000. The noise shown whilst the output shaft is spinning goes when the clutch lever's pulled in. Would a countershaft bearing noise disappear when the clutch lever's pulled in?


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Primary chain rattle? If it were that, could it damage the bike if the carbs were left without being synched for a time?


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It's a CB600F-Y Hornet from 2000. The noise shown whilst the output shaft is spinning goes when the clutch lever's pulled in. Would a countershaft bearing noise disappear when the clutch lever's pulled in?


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Primary chain rattle? If it were that, could it damage the bike if the carbs were left without being synched for a time?


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Oh, that bike didn't come to the USA till 2004. We call it a 599 here, not a Hornet. Took me a while but I found it.

If the noise goes away when there is no load on the clutch (lever pulled in)........
My best guess is a bad needle bearing on the transmission mainshaft the clutch runs on.

The primary driven gear is on the back side of the clutch housing so that gear rattling around would make the kind of noise you are hearing.
Luckily you do not have to go into the trans to get to the bad bearing.
But, Be POSITIVE you get the oil pump drive sprocket back in correctly while going back together if you do the job yourself.

If it came into my shop the clutch bearing would be the first place I would go.

Hope this helps. Let us know how it works out.
SemiFast
 

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Discussion Starter #10
Thank you all for your help and advice. I'm handing it over to a mechanic tomorrow for a deeper delve as I'm out of town for a couple of weeks. I'm pretty sure it's a bad bearing of some sort connected to the main output shaft. Will update all when I hear back. Thanks again.
 

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Thank you all for your help and advice. I'm handing it over to a mechanic tomorrow for a deeper delve as I'm out of town for a couple of weeks. I'm pretty sure it's a bad bearing of some sort connected to the main output shaft. Will update all when I hear back. Thanks again.
Could be, however the sound can travel thru the transmission and be heard at the output shaft (countershaft).
The mainshaft is shielded or insulated by the clutch, engine side cover and the main case making the sound hard to pin down.
It doesn't really matter because the service tech will have to remove the clutch in order to split the case so he can to get to the output shaft bearings.
If it turns out to be just the bearing the clutch runs on he'll find it when he gets the clutch off.
Just make sure you use an honest shop, that way you get what you pay for.

Good luck and happy trails to you.
SemiFast
 

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Discussion Starter #12
Thanks SemiFast, golden advice. I've had them recommended to me so fingers crossed. I explain the situation and ask for them to keep an eye for the clutch bearing before digging too deep. Interesting what you're saying about the insinuated innards and thrown sound, really hoping it means that it's not the main bearing on the countershaft. The bike's done 46k, so fairly long in the tooth, but rides beautifully and I love it to bits. If it's the main bearing not sure it'll be worth parting with the bucks, considering the mileage that's already been stacked.


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Thank you all for your help and advice. I'm handing it over to a mechanic tomorrow for a deeper delve as I'm out of town for a couple of weeks. I'm pretty sure it's a bad bearing of some sort connected to the main output shaft. Will update all when I hear back. Thanks again.
Could be! Honestly I don't even know if you have a primary chain at all - just sounded like what I was familiar with.

Good luck with the bike!
 

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I had a bike with a primary chain, the sound this one makes is very much like a primary chain noise.
So good ear cmonSTART. That was my first guess also.
After I found out what bike it was I looked up the parts breakdown, this one uses primary gears. So we started looking in a different direction.
It will be interesting to learn what the service tech finds.
 

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Primary chain

Norton used a single row skinny timing chain and a stamped cover with one central bolt, and a hard rubber gasket starting in 1934. It rattled and leaked oil for 34 years. Started on a 500 single, was still being used on 750 twins.
Finally in 69 they made a decent backing plate and cover with an O ring, a triplex chain and a diaphragm clutch. But Honda made a CB750.
Friend and I bought 2 750 Nortons in the South of London in 1971.
His bike ran out of oil in the primary case before we got out of London. The O ring had not been fitted correctly. Things got worse from there on.

Unkle Crusty*
 

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Discussion Starter #17
So, I've heard back from the mechanic and apparently the sound is coming from the cam chain and tensioner. They're not planning on replacing the cam chain and tensioner itself as they reckon it would come to £700 including labour. In my daze this morning I was over the moon, no bad bearing etc. But now thinking about it, I'm wondering if they've identified a different sound altogether (I'm abroad on work so am relying on email contact for diagnosis). Is it possible that the sound from a malfunctioning cam chain could sound as if it's coming from the transmission? I would've thought that sound would just be heard from the left side above the clutch housing.


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