hello, just bought a 89(i think) ds50. flatreed engine. easy starting, great idling, fast running, like 35 probably. its stock with 12/12 carb. anyways, so the problem is when i start to get about 2/3 into the throttle i start to get a crazy grinding noise that kinda comes in and out. i tried revving on the stand and i can sit there and rev all day but theres no grind. so it only happens like like 25-30mph. i checked the front wheel and it seems fine. feels like its coming more from the right of the engine. the covers are off and when i look under there while i rev i see nothing noticably wrong, but again it doesnt happen when on the stand. gotta be the variator right? ive never had bikes with a variator before. if it is the variator wouldnt it do it on the stand too?