weak/poor spark xt250 1980

[xtman]

Hi all, just found and joined this site as i'm trying to solve a problem. I have a gorgeous xt250 1980 which is almost restored to original condition. This is a true classic that needs to fly again! I have a problem with weak spark which makes starting sluggish and backfires and misfires at high rpm. I have had the pick-up and charge coils tested and have rewired the coils to the loom to ensure good connections. I have renewed the ignition coil,ht lead, spark plug and cap.The pick-up coil air gap is correct. The battery is good and is charging ok when running.Still weak spark. I'm thinking possibly CDI unit is faulty but don't want the expense if it doesn't cure the problem. Anyone please help the good weather is here.