I have a problem which just happened to my four wheeler last night. My grandson was riding my HO just cruising down a dirt road about 40 mph when something suddenly happened and the ATV started to bog down. He managed to get it home doing no more 10MPG to keep it from cutting off. It starts and idles fine but any acceleration causes it start to bog down and if you keep throttling up and it wants to cut off. It sounds like a diesel truck when clutched at a high speed deceleration. Can anybody give some ideas about what I need to check to figure out what is wrong.

Thanks,
Lee