Thanks for the replies and information. I really appreciate it. A little background on this project. Bought the Trailmaster MB200-2 and it came with a torque converter, jackshaft (10 tooth chain gear), 38 tooth rear sprocket and 196cc clone engine. I did a lot of research and spoke to several sellers before buying. Actual performance of the mini bike and estimate from research were very different! Top speed stock with throttle stop screw removed was 22 MPH on GPS and you couldn't even start on a slight grade. Bike weighs 165 lbs. and the heaviest rider, me, weighs 175 lbs. Not much fun for us to ride. Went with the Tillotson 212 which is supposed to be 10 hp. That upgrade produced 30 MPH on GPS. Added a Stage 1 (carb jet, header & air cleaner) that produced 34 MPH on GPS. Removed the governor for testing purpose, that produced the same 34 MPH on GPS. But, you got there a lot faster. Actually starting to be fun to ride! Testing with a tachometer while riding, actual top RPM running was 4,200 RPMs. On a stand, rear wheel off the ground, engine would rev easily to 6,200 RPMs. So, I concluded that I have a gearing issue to get where I want to go. My goal is to get this mini bike to top out at approximately 45 MPHs with decent pulling power. Riding range will be between 25 to 35 MPH. As a note, with Tillotson engine, Stage 1 kit and 38 tooth rear sprocket, this setup pulled fine under our current riding conditions. We have access to a couple of miles of groomed trails (20-25 feet wide) with long straightaways and open flat fields.
I currently have 10" of snow on the ground. Before the real snow sets in, I expect to have a couple of days of testing with my new build. Haven't been able to test the built engine yet. Also, have both a 50 tooth and 60 tooth rear sprockets. My initial plan is to start with the 50 tooth rear sprocket and go from there.
The reason that I like the Mikuni carbs is the anticipated overall performance gain throughout the operating range with them over stock jetted carb and smoother throttle response, feel and setup.
Sorry to be so longwinded. Just want to give as much detail as possible to assist others that are contemplating a Trailmaster MB200-2 mini bike purchase or doing a similar engine build.
So, am I heading in the right direction or asking for too much from this build? Thanks again for any and all comments and information.