I have a 2000 TTR90 with a Mikuni 19mm carb. The bolt spacing on this carb is 42mm center to center. All replacement 19mm carbs have a bolt spacing of 48mm center to center. Is there an aftermarket carb or adapter plate or intake that will solve this problem or do I actually have to get the Yamaha OEM carb. Is it necessary to have the carb heater on this bike? Will it affect starting or operation in any way.