Motor starts on first crank, runs like the day it was new. Had a friend use it and cleaned the carbs, has 2 carburetors, model is 25ESH. Well, as long as im cruising at low speeds it runs and idles great but when i go full throttle it may go for 2 minutes or 10 minutes but will eventually lose power. My top cylinder is cutting off, it doesn't immediately die and i can unplug the top spark plug and nothing changes, if i unplug the bottom plug wire it dies. My issues is obviously in the top cylinder. Also it's burning the spark pkug, i have to replace it and then it fires right up like nithing happened! If i go wide open it repeats. While my friend had it it cleaned the fuel tank, changed the bulb, and accidentally broke my pilot screw on the lower carb. I replaced both with the older style air/fuel screws or pilot screws as Yamaha refers to them. I put in the older style screws and new springs and set them to spec. Before i replaced them i had issues with it not idling and dying. Now it idles great but now can't run at full throttle and the burnt plugs are tan, whiteish in color and all indications point to my top cylinder burning plugs because it's running too lean. My concern is that the replacement screws are slightly different but I've read many on this forum who had the same issue and replaced, recommended to replace with older style because they're easier to adjust and may look different they function the same. Several members responded and also were pleased after replacing theirs as well. I just can't understand the motor running lean now after changing these screws and setting to spec, obviously it's starving for fuel. Any possible easy fixes or advice? Going to go into the carbs again soon to verify nothing clogged, my fuel tank is vented, no leaks, filter under cowl clean, and just curious if anyone has had similar issues and what was causing the problem? Any help is appreciated!