CB500 2001 gearbox knocking

salem1987 · Scooby Slapper Joined: 10 Sep 2013 Karma :

On the way to MOT the bike developed a strong vibrating noise under acceleration that sounded like the sprocket carrier bearing had failed.

Turns out the bike makes the noise if put in gear with no chain on, a heavy knocking sound at low rpms in any gear.
(If you know what a sprocket carrier/cush drive failure or knackered chain sounds like, its pretty much exactly the same!)

Clutch and basket are all fine and solid. Output shaft bearing has no obvious play either. All shafts i could get my hands on with the clutch casing off seem solid also.

Also no noise in neutral or the clutch pulled in, only when in gear.

Anyone got any ideas before i start splitting the engine?

MCN · Super Spammer Joined: 22 Jul 2015 Karma :

Pull the engine oil filter.
Cut it open.
Look for Jewellery. (Expensive shiny metal)
How is the crank connected to the g/box? Chain or direct drive?
TLDR post. Razz

Is this your Primary Drive? Aye/Naw?

https://www.google.kz/search?client=ms-android-samsung&biw=360&bih=560&tbm=isch&sa=1&ei=zU7bWv28HsjGsAWhlp2IBw&q=cb500+primary+drive+parts+diagram&oq=cb500+primary+drive+parts+diagram&gs_l=mobile-gws-img.12...0.0..12511...0....0.0.............mobile-gws-wiz-img.ylsYCEe16LU%3D#imgrc=eE8FG1CsssaePM:
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

salem1987 · Scooby Slapper Joined: 10 Sep 2013 Karma :

thanks for the advice.
after much time stripping the clutch etc with no success i checked the front sprocket.
I hadnt replaced it...

Embarassed

the hooks on the teeth from a knackered sprocket were causing the chain to ride up and make the noise.

Evil Hans · World Chat Champion Joined: 08 Nov 2015 Karma :

MCN · Super Spammer Joined: 22 Jul 2015 Karma :

salem1987 · Scooby Slapper Joined: 10 Sep 2013 Karma :

yes the noise was apparent with the chain off at low rpm's, but seems to have disappeared when riding now the front sprocket is fresh.

Odd i know, and probably doesnt make sense. But i can only assume i heard a noise with chain off and it was just the clutch/engine internals being a bit rattly at low rpm's.

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

Aye. Front sprocket was my first thought when I ready your post, then I saw the thing about it doing it with the chain off and you saying you'd checked the output shaft for play and thought it couldn't be.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.