Thanks for the comments. Bike starts and it's my 4th 4-stroke dirt bike. Hot start seems to work normally. It had more compression when I let the bike sit for a bit. The weather has been hot, but the other guys weren't having problems. I'm having a mechanic friend take a look as I've done no work on 4-strokes. I hope it's something simple and will post the results. The bike is brand new and started the popping and erratic idle after the third ride. I'm using good gas and the filter is clean. I'm a 2-stroke guy from waaaaay back.
I've only ridden the bike about 3 hours when it started to idle erratically (it idles high when you blip the throttle, but if you ride slow ,then it comes back down) and the engine would pop when chopping the throttle sometimes killing it. It's been hot, but I don't think it's that. Not overflowing the radiator. I stopped for a couple minutes and then went to start it and the compression was about half of what it should be. I bought the bike brand new and it worked great for about the first 2 hours. Any ideas?