Timing chain noise NX250 / AX1 Engine

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A new NX250 (or AX1 it's identical with MD21) engine runs mechanically very quietly. Over time, however, you will hear a faint rattle that gets louder as the mileage increases. Often the chain tensioner is held responsible and replaced unnecessarily. Therefore, before replacing, check the function viewtopic.php?t=2529 .

But in most cases only the timing chain is worn out. It stretches over time. A stretched chain can be recognized by the fact that at top dead center the marks on the camshafts are not horizontal. For checking the marks refer to viewtopic.php?t=2109


Elongated timing chain after 50,000 km

In addition, the inner links wear out. This causes the chain to slacken back and forth, turning back the tensioner. This causes the rattling mentioned, which does not go away even with a new chain tensioner. Mass outs fix viewtopic.php?t=2534 can be used as a temporary solution, but a new timing chain would be better.


worn out timing chain at 50,000km

Never use replicas from China - a broken chain can cause a total loss. For the same reason, don’t use a chain with a rivet link, otherwise you have a potential weak point. The original Morse (Borg Warner) chains are still available from Honda https://www.cmsnl.com/honda-nx250-domin ... 401kw3003/

There are also Japanese DID chains part number DID-SCA0409A-126L https://www.mvh-shop.de/Motorrad-Steuerkette-endlos_17 I've used DID chains on a few engines and so far they're running without any problems. It remains to be seen whether they will last as long as the Morse chains. There is a howto for changing the timing chain here viewtopic.php?p=4799#p4799 - I can post an English version if required.