Lash or play in EX or DX 6 Gear Model??

[xNE0x_imp]

Check your chain alignment with a tool. Takes 2 minutes, and you can get one on amazon. Then, I would check chain slack. I usually like to see about 1/2 an inch of slack on my chains, regardless of spec. You will feel some "play" in the drive train of a chain driven motorcycle, but not the gearbox itself. Changing your oil, will not change this effect.

Also, pull the chain cover off in front to check gear wear. If your chain is not straight, it may have developed a really bad habit on the gears themselves.