I tend to rely on cam profiles and timings for which the power outcomes are known. In Tuning For Speed there is a list of cam timings for various 50s racing bikes. When I think of a commando, I think of the 1959 AJS 7R - the best 350 of the era. As a benchmark I think of t he E3134 Triumph cam. If you fit it to both the inlet and exhaust of a standard Tiger 110 which normally used E3275 cams, and use the factory specified timings, and lengths of inlet and exhaust you get a torque increase right across the rev range, a pronounced cam spot at 4,000 revs and much more top end. That cam is replicated in a lot of very fast bikes of other makes. For a commando with the long stroke, heavy pistons and suspect bottom end it is too much. So in effect I've relied on anecdotal evidence and my own common sense and experience as to how I've timed my 850, and set up it's inlet and exhaust systems. I've advanced the cam 12 degrees to compensate for the back pressure of the two into one exhaust, and open the inlet earlier. However the closing points are not optimal. It seems to work very well, however I believe that is just partially a fluke. As far as profile is concerned, a safe lift rate and closing rate are essential. Triumph GP racers had severe cams and were valve droppers, that is why the E3134 was developed. Ed Iskinderian's polycyclic cams were way beyond me, and I don't know if the theory actually worked in a motorcycle engine. I suggest that lightening the valve train in a commando engine is pretty pointless, it will probably cop 9,000 RPM with our most ferocious cam for a while without causing much trouble, and we never go near that without a bottom end failure first.
