I have a rampage xt. I installed a new engine last year. I broke it in and ran it for a couple of hours, It was running fine until I noticed it was running rich. I tried leaning it out a bit but it still acts like it's running too rich. I can't lean it out any further. I fouled out too many spark plugs. I tried gaping them. but it didn't work. I even installed a new carb thinking it was defective. But that didn't work either. If it's not the carb or the spark plugs could there be something internally wrong with the engine itself? Also the throttle response is delayed for example if I quickly throttle it and release it bogs down and then recovers. over time this leads to fouling. What could cause this delay?