Hi Lord Moonpie
I also have one of these mini-beasts waiting in the wings (must finish the CR750 & Dresda GL1000 first!) and am mesmerised by the engine. I went to Spa Francorchamps last weekend and there were several superb RC163 replicas there and I took great interest in them. Some, not all, literally screamed and must have attained 20,000+ rpm cleanly whilst others misfired at high revs. Some have the Keihin FCR carbs and others did not but some were running well on standard carbs without the airbox (incidentally, I already have a jet-kit to permit standard carbs and no airbox). I am no expert on the engine but have done some research in Japan via my contacts at Honda who have reported that the engine is pretty well unbreakable, even at very high (20,000) revs. It is common in Japan, apparently, to fit FCRs and a new ignition module to everyday roadbikes make these incredible engines rev to 20,000 rpm and 22,000 has been reported! I am told that 'the engine was an exercise in attaining high rpm by using 'very low mass and perfect balance'. I was told this personally by an HRC technician I first met when I worked for Bel Ray in the 1970s and we were involved on the lubrication of the NR500. I asked if tuning equipment was available and he said it was not possible to tune it more - so there is a challenge!! I intend to fit FCRs, the modified ignition module, "blueprint" and remove the alternator. There is a "story" at Honda that Irimajiri, the lead designer of the Honda RC174 (250-6) was given a "clean sheet" to design a road bike engine as his legacy before he retired. Apparently, the result was the CBR250RR. These engines running open exhausts do sound like nothing else!
