There are many brands of Internal throttles available. Some made abroad will not fit your 1" grips without remachining the grip to make it fit inside. Others will fit but are hard to twist, A company called Streamline Designs offers a "strret legal" internal throttle running smoothly on bearings. The twist needed to reach full throttle is also much shorter than older designs. Result: no more re-griping to reach full throttle. Exactly the way it should be. This company also build a few full blown custom bikes. Streamline Designs.
i can honestly say this is the best throttle on the market after trying all types of internal throttles. my bikes have always had internal throttles to keep the lines hidden and clean, i have encountered many problems with binding and breaking of cables and uneven operation, Austins throttle has corrected all of the problems associated with internal assemblies, this is the only throttle i will use, ease of operation, ease of fabrication, but most importantly safety, you dont need a sticky throttle on a new customers 124 inch turbo bike,this throttle is currently in use on my twin engined bike and it easily pulls the lever of a holley 750 car carb. so it will easily pull a mikuni or s&s,i hate to sound like a commercial but i wouldnt endorse it unless it worked.