Norman White told me once that getting power from these motors is ‘all in the head’. And that has stuck with me whilst I’ve been playing around with mine.
My main regret is not putting mine, a mk11a, on the dyno before I started out modifying it.
As purchased, it ran well, I’d say better than most (as attested to by a member on the forum, it was ‘ a good un’).
It had a single 36mm Mikuni. I checked the CR and was surprised to see it was actually only 7.6:1. But I would estimate it had somewhere between 35-38 rwhp.
As you say Ken, all those owners who think their stock Commandos are putting out over 50rwhp and their Combats 65rwhp are sadly deluded !
Hence my regret, I’d have liked to have known the starting point for certain. But never will.
My ‘mk1’ build was with JS1 cam, 10.5:1 JS pistons and long rods, 35mm FCRs, Tri-Spark and box stock RH10 head. It clearly had more torque everywhere compared to prior, and its power above 4K was light years ahead, previously it just ran out of breath at 5k, afterwards it stomped right past that with ease. On the dyno it peaked at 56 point-something rwhp, so probably a 20hp increase.
My ‘mk11’ build was as above, with Comnoz top end treatment. This included bigger inlet valves, careful porting job, and a slightly tighter radius on the tappets aimed at sacrificing a little peak rwhp for more torque lower down.
Nevertheless, it still blew me away when it showed 64 rwhp. That much improvement from only the head really, really surprised me.
So it currently has probably 28hp more than when I started, which is a 77-78% increase!
It’s a shame I didn’t have a FA head to do this with, I just used my existing RH10, which is not as good a basis as one of your heads. But it still goes to show how much potential there is in these motors just ‘in the head’.
