The infamous Popping.

[Builds4Christ]

You can also check for intake leaks behind the carb. Get it running and spray starter fluid around the seals / gaskets / spigots … listen for rpm change. If the rpm’s go up or down, there’s a leak.

what’s going on here in the photo?
Like I said I’m not familiar with these engines and the photo doesn’t show it great.

Did somebody nibble on the intake?
Is there a visible gap?

View attachment 150505

That's weird. That's not what it looks like when I look at it at all lol. I think its just reflected light, but its part of the intake tube plastic. Looks normal outside of the picture.

 

[bob58o]

Well besides a damaged valve or spring, I think you looked all the stuff that came to my mind.

No leaks in intake or exhaust.
Valves lashed properly.
Larger pilot jet.

Check out a few dirt bike 4 stroke pilot jet tuning videos to see if the jetting seems correct.

A different, more tunable, carb might help get it dialed in at part throttle.

Instead of just a pilot jet (and idle circuit adjustment screw) and a main jet… The carbs I use also have a needle height adjustment which (along with other things) helps tune the carb between idle and wide open throttle .

Some carbs have different needles to also tune more of the region between idle and WOT.

 

[bob58o]

This is the best video I’ve found to teach how to tune a pilot circuit.