I hope this don’t come across as a dumb question. But I have a 2002 CR250. It runs great! Fresh top end. Plug burns a nice tan brown.My question is when riding up a flat road and the strain is on the engine it runs smooth. But if I back off on the gas just a little it sounds sputtery! But if I hit the gas there is NO hesitation! I can be at 1/4 throttle 1/2 throttle or anywhere. Long as there is a little strain on the engine it is smooth as a kitten, its only when the strain is off the engine maintaining the same throttle position. Just wondering if this is normal! Any help would be great!