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:

https://www.china-parts.co.uk/acatalog/ZS001147L.jpg


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?

Is it possible that the swingarm bushings are worn?

Well, they sure aren't new (factory originals on a 13-yo bike), but I have been able to tension the chain and cancel any noise until now...


Then again, I had the rear brake drum shoes swapped out a couple of months ago, and I noticed that the mechanic who worked on it made two asymmetrical marks on the adjusters, which however I evened out during my first attempt at retensioning, thinking that maybe it was a mistake on his part... or was it? :hmm:

Are the sprockets aligned? Setting the adjusters the same actually causes misalignment sometimes as parts aren't welded square.

Well, at this point I will re-set the adjusters on the mechanic's (asymmetrical) marks, and take it from there. He probably knew a thing or two more than me when he did that :shrug:

I have no idea if your bike has the rubber or plastic chain guide/swing arm protectors like the hawk/tbr7/brozz, but if it does, and if its worn through or missing, I'd imagine its make some noise no matter how the chain was adjusted.
Hey I'm just throwing out ideas. Lol

It seems that he did that to make sure the sprockets were aligned. Motion pro makes an alignment tool that works well and is fairly cheap. I bought one and have used it many times.


https://www.amazon.com/Motion-Pro-08...s%2C217&sr=8-5

I could try and shop for something similar locally, but I can also jury-rig one from some long-ish metal beams I have. I'll drill two holes through a couple of them, and bolt them on the sprocket while doing the adjustment.

Yep, should work. Even a wood dowel clamped to the sprocket would probably work. Just need something straight and long enough to go along the top of the chain.