Hey Murray,
I had the same problem with my Mikuni Carb springs being 'heavy' also. Not sure where I read it, but this matter has been addressed before and the solution was to shorten the existing springs. I shortened my springs by about 25%, a couple of turns for my springs, then flattened the cut portion of the spring, with a Dremel wheel, so there was not a sharp edge cutting into the cap of the carb. This made the throttle pressure a lot more manageable and kept the throttle in place with standard friction on the quadrant. It made sense to me after someone pointed out the stronger springs were in place on these carbs to keep the slides in place during rough terrain dirt bike rides. Not sure if that was the real reason, but I bought it hook, line and sinker... the cut springs work for me - your mileage may vary.........
