Unpredictable power loss

[Milo_R50]

I have a Roughhouse R50, 2015, 7500 miles, stock except rollers and clutch springs, de-restricted.

I've been getting this problem since last week, when I cruise,sometimes the engine seems to lose all power suddenly, it goes down to near idle and it will not rev when I give it gas, the sound changes, and I slow down to a crawl.
It is not the classic vapor/vacuum lock because I ran it with the gas cap half on and it still happened.
It's not predictable, last night it happened once on a 35 mile cruise.

And when it happens, I shut her off, fire it up right again and I can take off with normal full power as normal as if nothing is wrong.

Things I have done so far after this started to happen:
removed airbox and inspected air filter
new fuel filter
Checked for blockage in fuel lines, applied vacuum to the petcock and fuel flow is fine.
cleaned carb twice(wasn't dirty)
checked all wiring
removed and inspected exhaust and cleaned off some carbon
Cleaned and sanded all grounds, electrical connections
Inspected reed valves, no cracking or warping, good condition.
replaced spark plug


Still getting it sometimes. I use the scooter everyday so it's not old gas.

Any idea what this could be??
The scooter has no trouble starting/idling.
I'd appreciate your reply with some ideas.
I'll try and get a video next time it does it.

The fact that I can shut it down, fire it back up immediately and it's fine makes it very confusing to troubleshoot.

[Milo_R50]

OK so it just happened again.
Here is a video I made of how it gets.
https://www.youtube.com/watch?v=3fwpjRq ... e=youtu.be

I'm giving it full throttle there, and thats as far as it will rev.

And here is it, after shutting it off, and starting it right back up.
https://www.youtube.com/watch?v=oK08hFL ... e=youtu.be

As you can see, back to normal, running and revving happily.

On the way home it sputtered again, I pulled off to the side, let it idle for 20 second, and I could take off again with normal power, that time I didn't have to shut it off for it to go back to normal.

[Stanza]

It almost sounds like a misfire, but you'd think that would affect the idle as well. Have you tried running it without the airbox? If not, if you can get it to replicate this behavior on the stand (maybe revving it for awhile as if you were out on a run?), try partially blocking the mouth of the carb with your hand to restrict airflow and see if that improves or worsens the symptom.

[Stitch]

Spark plug wire?