My first sled w/power valves, now have about 850 miles. Can't get much more than 70 mph when accelerating from cruising speed...but from dead stop it will go past 100 like it should. Plugs don't make a difference. Is this the power valves?? Or the fuel/air screws in carb? Have also noticed oil spitting out of left head/pipe joint. HELLLLPPPPPP!!