So you're saying retarded to the point that we go through power stroke, through exhaust... and arrive at intake with the charge still burning because it fired so late?I have no idea what kind of ignition is present on the '03 Bullet, but I've seen carbies blown out of the boots on several XS650s when the following conditions were present: Points ignition, advance curve stretched due to worn bob weights in the advance governor, timing set at full advance with retard timing left to fall where it may, with said retard timing falling close to TDC (way too retarded). I have never seen XS650 carbs blown out of the boots without finding severely retarded ignition at full retard and worn weights as described.
In my full advance scenario you'd expect (require?) the kick starter to kick back pretty severely. Lacking that kickback, I'd say that too retarded is the more likely scenario.