I recently bought a beat up old 200m that's had a bit of tampering done to it. I cleaned the tank and the carb, and changed the oil an plug as ithad been sitting for a while, pulled it once and it fired right up. But when I try an maintain a speed it spits an goes, backfiring, cutting out. Just wondering if anybody has any ideas or has had the same problems. Also dosent have much of an exhaust system so I don't imagine it's getting proper back pressure ether.

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