Noticed on my newly purchased 07 Grizzly 450 (bought it with 170 miles on it), that if I use 1/2 throttle or more for a short distance (1/4 mile) or more (35-45 mph), it'll backfire through the exhaust once I begin to decellerate (pretty loud backfire!). It backfires around the time it slows down pretty much.

It does this every time I've tried it so far (around 4-5 times)

Thanks in advance,
Jeff