Stage II stalls going downhill at light throttle

[Ochlockonee]

Alright diagnosticians, here is a good one and I promise I'm not making any of this up.

My bike is an '05 classic with a straight up Provo stgII setup. Uni filter, 95 main jet, needle:middle. I know it's a tad rich and could stand a 90 main jet but it ran fine for over 1000 miles just like this.

While travelling down even a light grade at light throttle the engine shuts off like someone hit a switch- without any warning. This would lead one to believe it is an electrical problem but there is a catch. If I leave the throttle in the same position the engine does not fire for up to 15ish seconds. If I manipulate the throttle the motor always wakes up within 2 seconds after I start twisting. I have tested this 30+ times and am absolutely sure the engine does not start firing coincidentally after I start twisting the throttle. Replacing the plug changed nothing. Leaning out the idle jet (screwing it in a bit) also changed nothing. It gives no indication before the motor dies, no stacatto popping like it's too rich, it just dies.

[~cheap_ride~]

are you sure it dies? maybe just idling and you dont hear it due to road noise? my zuma does this, but i dont think the engine is quitting, just quiet if im not on the throttle and coasting down the hill. when i get to the bottom i give it gas it wakes right up and pulls hard.

[OldGuy]

If it is actually dying and it only happens going downhill the first thing that comes to mind is carb float level. Try raising it just a bit.

OldGuy

[StepVino]

Any chance you might have water in the bowl? It's kind of
a stretch, but maybe when inclined, the water moves right
under the jets. Once in the needle tube I can see how moving
the throttle might help clear it out.

[Ochlockonee]

Update: the piston is damaged. One one side of the piston ring gap locating pin the piston ring has widened the ring land to about 3 times it's normal size. I have no idea why this happened. I use the oil injection with synthetic oil, the carb is set up safely rich, I use 93 octane fuel. I'm pretty bummed right now.
I tore the motor down because I got more symptoms and the ones I already had were only getting worse. Compression test yeilded 60psi.

[StepVino]

Bummer... I'm sure you'll get it going good as new soon.
Just stay away from hammers and other heavy projectiles
while around the scoot. ;wink)