CLUNK CLUNK CLUNK when decelerating - Now what!?

Over the last about 48-72 driving hours I noticed a clunking sound when decelerating. It is in time with the front sprocket. Now it is radical noise when slowing down and when coming to a stop it's a fast clunk then slows. I was thinking oh great after all the money I sunk in this pit the transmission is gonna blow up. In the driveway, in neutral (no engine running) I can roll it fwd and rev and there is a loud "clunk clunk" as it moves. This leads me to think it may not be the transmission but something else.

I did have the front pulley off last year to replace the GBPS sensor, it was fine with no red dust or cracked/broken grooves. Put it back together with a fresh bolt from cheapcycleparts.com, torqued to the higher spec. It shifts & accelerates smooth as butter. The clunking doesn't come to the back tire (no jerkiness) when it is slowing down.

I am clearing out a space in the garage to jack it up and take the belt off to start with rocking the front pulley to see if there is a lot of play, then take it off. Looking at the drive system on cheapcycleparts (clutch plates out to front sprocket) I don't see what could wear down and and make a gap or something.

It may be my imagination but I swear I hear same noise on all GS/RS on when it's moving, but it really quiet. Maybe whatever "moves" or has a gap just cracked or broke. Clutch basket maybe?

I imagine some gear head has seen (rather heard!) this before and might know what it is I am praying!! :pray:

Thanks!
Steve

Yeah. That same thing just happened to me yesterday. I just put up a post before I read your thread.

Check ALL the teeth on your drive belt!!!!!

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Originally Posted by IGETAROUND

Check ALL the teeth on your drive belt!!!!!

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And check the teeths of the front and rear sprocket for a rock wedge in there.

Turns out it was the front pulley. Inspected it 6 months prior it was fine. After taking out bolt it wobbled on the shaft badly. New one installed, runs great now.

Glad it's resolved. Thanks for posting the update.

Can An has not fixed front sprocked problen, it could fail again... should be checked every 3K miles or sooner.

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Originally Posted by Bruiser37

Can An has not fixed front sprocket problen, it could fail again... should be checked every 3K miles or sooner.

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I have a '16 F3, low miles, and when I removed the panel to check the sprocket this spring, there wasn't "rust" showing outside, or anything on my fingers other than normal grime. Is there any other way to check, short of pulling the sprocket? If I do that, do I put anything on the new bolt threads?
I've read about using Assembly Paste for the sprocket and have an order on the way "just in case".

I wouldn't use assembly lube. I would suggest instead using a Moly paste. They are designed so that the carrier evaporates and it leaves behind the moly lubricant.

You can check the front sprocket by lying on the floor with a flashlight and looking up at it. If its covered in red dust, its dead. If its still black, its likely fine.

The moly paste (not moly lube) used on the splines (not the bolt) is not the same thing as assembly paste used in engine assembly.