Chain and trac dynamics swingarm rd400 question

[Striker1423]

You should have about 1 inch of play in the middle of the chain at rest.  Just press up on the bottom of the chain near the middle and measure it. Give yourself 1 1/4" and ride it. The chain should not be a guitar string. It wears everything out fast and in a hurry if you do that.   

[Dvsrd]

If you end up having to buy a new chain, I would recommend going to a #520 with an alloy or Supersprox Stealth rear sprocket, for some weight savings. DIDVX3  X-ring chain is a nice one. With today's chain availability, #530 is total overkill on a 350/400. People use #520 even on 100-150 hp bikes.
Running a too tight chain may end up damaging the countershaft bearing (the bearing just inside the front sprocket), possibly also the rear wheel bearings. I always check chain tension when sitting on the bike, loading the rear suspension.

[rd400greenhorn]

Yes i found about those 520 to late 😉

Oh well

Measuret in the middle or the chain, from the bottom,
Around 3 cm of travel if pushed up.