During the 70´s, the local fools providing insurance (mandatory here in BC at that time) caused the motorcycle companies to downplay their advertised horse power ratings to the point of stupidity. Of course, along with that bs came the obvious problem of stating top speed capability. If the 76 rd 400´s red line is achieved in the high gear, the speed will be considerably above the published statement. Although one would want to look at the Salt Flats Records for a proven performance level, i will offer the fact that one of these antiques has pulled consistent 10:80´s at the local Ashcroft 1/4 mile. You don´t get a 10:80 from 42 horsepower without adding the Nos. As i possess the original 76 rd 400 owner´s manual, and the original 1976 yamaha service manual, i´ll quote the performance numbers given. The owner´s manual states nothing regarding performance, but the service manual does. Section 7.2. SPECIFICATION "4" is about performance. 1) Maximum speed- 160 kmh(99mph) OR MORE. Then 4) 0 to 400 meters Acceleration Time- 14.0 seconds. 6) Fuel Consumption- 32 km per litre @ 60 kmh. (74 miles per gallon @ 37 mph. This info is quoted from the Yamaha Service Manual. Note the "Or More" statement regarding the potential top speed. I would suggest the 1/4 mile numbers suffer due to excessive tire spin, and the top end due to factory "averages" based jetting.