If it's blue smoke all the time (sitting at idle & while driving), it's most likely the oil control rings. A compression test won't expose that problem. But if the oil control rings are bad, it's likely that the compression rings are also bad (might show low compression). If only under heavy acceleration, it's the valve stem seals. The vacuum created under heavy acceleration can cause oil to be drawn past worn valve stem seals. This info is from many websites on automobile engines. ATV/UTV engines aren't much different.