Just purchased a 93 softail at a great price (I hope) it runs pretty good but I needed to keep the choke out. plugs look to be running very lean. Tore into carb and replaced slow and primary jets 40 and 175, runs better but now keeps backfiring on startup only wants to run with choke half way in. While riding if you throttle up very fast backfires and misses. Any ideas or help would be deeply appreciated.