I've had a few xtx and R's and have sorted most things out but this has me stumped. my xtx is backfiring at about every 3-4 seconds at say 2000rpm. I have tried swapping parts like a different injector, spark plug, coil and cap, new fuel, charged battery, but still its playing up. just wondering if this could be a result of a bad key in the stator?

any comments appreciated guys!