Chain rattling but slack in spec?!

ChillRider · 02-03-2021, 01:42 PM

As per title, I have mounted a new JT chain (428HDR2-122) on my ZongShen LZX 200GY-2, to replace the old, clapped out RK 428HD chain that it had before, as I had almost run out of chain adjustment notches and it needed re-tensioning every 200km.

I have installed the new chain in early October and put about 2500 km on it so far, with no retensioning necessary and quiet operation. The sprockets looked and still looked OK to me, so I let them be.

However, in the last 400-500 km the chain has started rattling and slapping noisily, yet when checking for slack it appears in-spec, even if at the limits (manual says 20-30mm, and indeed I measured just about 30mm of play, give or take).

A couple of times I deemed the clanking to be so bad that a retensioning HAD to be necessary, and yet when I loosened the rear wheel and tried to give it one more notch on both sides, the chain just became too tight, so I backed off.

Now, this bike has Yamaha TW200-style snail adjusters even though the equivalent Yamaha part has more notches:

What gives? Is this kind of adjuster just not fine enough for cases where chain slack is just at the limit? Maybe it's one of those cases where an asymmetrical adjustment might be needed? Or can worn sprockets cause this?

02-03-2021, 01:42 PM	#1
ChillRider Join Date: Jun 2020 Location: A small country with a funny name Posts: 164	Chain rattling but slack in spec?! As per title, I have mounted a new JT chain (428HDR2-122) on my ZongShen LZX 200GY-2, to replace the old, clapped out RK 428HD chain that it had before, as I had almost run out of chain adjustment notches and it needed re-tensioning every 200km. I have installed the new chain in early October and put about 2500 km on it so far, with no retensioning necessary and quiet operation. The sprockets looked and still looked OK to me, so I let them be. However, in the last 400-500 km the chain has started rattling and slapping noisily, yet when checking for slack it appears in-spec, even if at the limits (manual says 20-30mm, and indeed I measured just about 30mm of play, give or take). A couple of times I deemed the clanking to be so bad that a retensioning HAD to be necessary, and yet when I loosened the rear wheel and tried to give it one more notch on both sides, the chain just became too tight, so I backed off. Now, this bike has Yamaha TW200-style snail adjusters even though the equivalent Yamaha part has more notches: What gives? Is this kind of adjuster just not fine enough for cases where chain slack is just at the limit? Maybe it's one of those cases where an asymmetrical adjustment might be needed? Or can worn sprockets cause this?
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