sounds like you need to do some low speed tuning stuart.
i love how the title of this thread changes with the latest posts/moods.
bike speedos are extremely accurate if the circumference of the tire is accurately measured, like rolling through some oil for a few tire revolutions, (with you on the bike) and taking the average distance. the only problem i had was the vibrations would destroy the screen. i just installed one of these yesterday.
it has a thermocouple that goes under the plug washer for head temp and a quality speedo