On a recent piston ring replacement job at 9,900KM (due to ingress of dust) I was surprised at the lack of tension on the cam chain and when I released the two bolts found only 3 to 4mm left. upon lifting the chain at the top of the sprocket, even under tension it was a good 1.5mm. I found similar wear on another engine, also at the 10,000Km mark. The tensioner had deep wear marks on the plunger on opposite edges too.

On the GS Moon 260, (Linhai 170M) cam chains they wore out so quickly it became policy to fit new Yamaha ones from new. the original ones lasted a few weeks whereas the Yamaha ones last a good year or so.

Seems that, although much heavier and wider than the Linhai one, the Chinese still can't make a decent cam chain so Suzuki or DID replacements coming up, the tensioner also looks the same as my Suzuki AN400 Burgman one.

Update on cam chains.

DID part is;
DID SCR-0409SV 122LE

Chinese OEM maker is CHOHO

Having reviewed the other 10 Z550Ex's we have seen that the slack chain on #18 is unique, all the others are OK and well within limits, so at just 0ver 9,000Km it is a mystery, also the auto de-compressor broke off the arm since the last inspection and that and the spring are somewhere in the crankcase so best route in to find them was via the alternator side case. little job turns into a big one and now we have to wait for the replacement part and a new gasket to arrive. Grrrr.