I've done a few things to the bike over the winter. I finally got the tubeless (yea, it actually worked out dandy. I'll fill in the details) tires on and the chain drive all finished up. I also put a raptor petcock on and heres where I may be stepping backward. After finally having gotten all this stuff finished I went for a ride. Seems after a few minutes at about half throttle the bike starts to sputter and wants to stall out. Anyone else have this issue after switching petcocks?

i did. that was my first thought. I plugged it with a small screw and liberal amount of gray seal. I went ahead and globbed it up good with gray seal so if there a vac leak it should be gone tomorrow. Fingers crossed. If that doesn't work Im going to switch back to the stock petcock and see if that clears it up. Any other ideas what might be the issue?

If you put your old petcock on does the problem stop?

Sounds like the gas in the bowl is too low, check the float level. You can stick tubing on the little Spout under the bowl & run the tube up past the upper edge of the bowl, loosen the Drain Screw & lower the end of the tube, OR maybe the flow rate IN is too slow to keep up with the engine,, that sounds mo like it..You can prove that by strapping a container on the seat & run a hose to the carb & go ride. If it holds a quart, fine..just have stuff to hook up the tank & carb if you run out.

haven't messed with the carb yet. Going right now to try the old petcock. fingers crossed.

only seems to happen under a load...sort of. I live on a steep hill. No issue getting up this hill as long as Im not trying to gun it. Anytime I "gun" it hill or flat land it'll sputter. In neutral i can rev it up just dandy.

I'll assume your using the stack carb (?). Something to check/clean is the throttle off by pass circuit. This is controlled by a vacuum diaphragmon the side of the carb - circular cover with three screws holding it  on. The drilling to the vacuum side is really, really small and it's possible that it's got pretty crusty while the bike was sitting.

Your symptoms aren't what I'd expect, but it may be worth checking.

The other possibility is ignition coil. A problem here can only surface when the coil gets hot. Once the coil cools, problem disappears again.

gave the carb a good cleaning. Its well nigh spotless. It helped but didn't solve the issue. I also got a look at whats in my carb. 45 pilot 145 main. Didn't look but I'm wagering heavily that I've got the entire white spacer in there too.  Im pretty sure im not running rich considering that and especially because all last year i used a well soiled air filter that had to block some air flow. Ive got to be even leaner now with a crisp clean filter. Can being overly lean cause these symptoms I've described? Using last years plug. Probably shouldve started with that but...i suppose it's possible the spark is strong enough to ignite the smaller amount of fuel while on the pilot circuit but too weak once i throttle past it. I don't know. I didn't do a freaking thing to the carb or engine (barring valve adjustment) so I have no idea why I was running just dandy last fall but now im not. Still taking suggestions.