Posted by keith on November 21, 1999 at 10:26:55:
Some advice in this forum belies a fundamental misunderstanding of carburation. I admit that I am not familiar with the specifics of the Mikuni carb, but consider this. All carbs have several independent and specific circuits, i.e. idle, transition, intermediate, cruise, power, accelerator pump. Each circuit is designed for a specific driving condition. By re-jetting, or removing the white spacer, you will effect exactly one circuit, the cruise circuit. The best bet for increasing performance is probably carb replacement, but beware. Using a carb with a larger diameter may decrease performance in the low rpm ranges. A larger diameter carb decreases the velocity of the fuel-air charge in the rpm ranges you spend most of your time. Decreased velocity of the fuel-air charge leads to decreased vaporization of the charge. In addition to dumping raw gas out the tailpipe, insufficient vaporization negatively effects the burn, decreasing performance. A larger flow (diameter) carb is useful in wide open throttle conditions where you just want to pack more fuel-air charge into the combustion chamber. But remember, you may sacrifice all the lower range performance charactaristics of the engine in order to obtain high rpm horsepower, this is what most raceing vehicles are designed to do. Essentially, carbs are intricate and complicated devices, (thats why injection is so superior).
There is also a parallel between the above discussion and the exhaust system. A less restrictive exhaust does sound great, but is unlikely to effect performance in any but wide open or near wide open throttle conditions. But unlike a high flow carb, a non-restrictive exhaust system is unlikely to decrease performance under any condition.