Hi Harry. My dealer told me that this is product of the general setup of the injection. Below exactly 80 degrees centigrade and 3000 rpm the rear cylinder is switched to "half" its normal operation. Apparently this is to keep the rear cylinder from burning itself out. I have been told that that was a problem with the 2000 version, and that this is the solution of that problem in the 2001 version. It may be so that later versions have different solutions, in which case you could consider a more recent injection control unit (expensive!). Otherwise keep your eyes on the temperature and the rev counter.