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Discussion Starter · #1 ·
last week I replaced the original Triumph chain and sprockets with a DID chain and JT sprockets.

comparing the Triumph front sprocket to the JT have noticed that the original has rubber discs or collars bonded to either side of the sprocket whereas the JT is just plain

at first I thought the rubber discs were some sort of dampener. but now I think it's to support the chain link side plates as they rotate over the sprocket teeth so that the chain rollers are not in contact with the root of the sprocket teeth making for a quieter operation.

is this logic correct?

my old chain and sprockets were so badly worn that the new parts have made the bike run like a dream so I cant say if its quieter with the JT sprocket or if the original is better. however, I have noticed that when I push the bike you can hear the chain engaging the front sprocket quite clearly now.

so, seeing the front Triumph sprocket was more eleborate and thus more expensive I guess there is some logic to that design.
 

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The earlier bikes also had a rather complicated foam damper attached to the inside of the front sprocket cover for the same purpose. It actually just filled up with chain lube and crud causing a foul mess and was deleted at some stage as useless, surprised they still do the O-ring thing on the sprocket.
Phil
 

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I wonder if EPA/DOT tests in the USA look at total noise (ie, drive by noise)? My Kaw W650 also had a rubber ring of sorts bonded to one side of the countershaft sprocket. I'm thinking it's a noise-reduction device to lower overall bike noise.

I've noticed none of the aftermarket sprockets (I've seen) bother with it.

Bob
 

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I just changed the engine sprocket today, from 18T to 19T and the original had the rubber sound-deadening on it, which quite threw me for a minute or two.

G ; )
 

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Discussion Starter · #6 ·
just an update. have noticed the new sprocket it is definitely more noisier. could here it clearly on the way to work very early this morning while no traffic was around.
it now sounds like, well,,, a chain being dragged over a sprocket... at high speed. so I guess you could say the bike sounds more "metallic".

seems what ohiorider was thinking is correct - noise-reduction device to lower overall bike noise.
 
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