My K1 is about 110-120 miles to reserve. My K5 is closer to 130. I recall my previous CB750s (all early bikes, 71-72) being similar. I don't know how far reserve will get me, but I've gone about 30 miles into reserve a couple times before fueling. 150 miles should be a safe estimate. I wouldn't push much past that without carrying extra fuel or running yours out to know for sure.