I just changed over my chain and sprockets. EK x ring 520 chain and 520 AFAM sprockets. Brand new. The chain slack looks good, everything is aligned. When I run it on the stand and put it in gear, it pops and jumps. Not every revolution, but it sounds bad enough that I'd be uncomfortable riding it. ANy ideas?
Do like Rain Man, ride it slow in the driveway, should be fine.
Your bike's motor running less than perfectly smooth, maybe during warm-up ... the motor gives tiny extra pulls on the chain (very minor surging), the wheel accelerates quickly easily because it's under no load, and each time the motor slows back down the wheel is going too fast but has nothing to slow it down except for bunching the chain up on top of itself and or the sprockets.
You could also try it again with just a touch of rear brake ... just enough to put a small load on the rear wheel.
The factory chain and sprockets weigh a lot more, possibly enough more that it loaded the rear wheel sufficiently to not out-race your motor. That, or maybe your engine was warmer and running smoother?
I did the same thing today, ran my bike on the stand after installed a DID 520 chain 15/43 gearing. The chain jumped around and made a huge racket. I took it off the stand and rode it around, all is good.