Some new jets arrived from Bing, and I spent a few hours installing them and rebalancing the carbs. Voila ! The big lag seems to be gone. We now have smooth acceleration, and the bike is fine under load. A few finer adjustments may still remain, but things are much better and I took the bike for a 45 minute ride to test things out. It seemed to run even better as I went along, but that may just be in my head. I got back and stuck the carb balancer on the bings again, and they seem to be pretty even. I am much happier for now, and can concentrate on getting a few more hours on the engine before I change the oil, check the valves, and re-torque the head. The bike is also lower than the R50/2 and the Euro bars make it feel much sportier. So far, so good.