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Mikuni VM36

If you have a stock motor ,then I tend to agree with Morm. If you haven't read the tech section ,and aren't familiar with the  spacer mod ,tuning the mix screw, or jetting ,you haven't realized how surprisingly  well the bike can run with the stock carb.(the mods above costing only 10 -20 dollars, and you can use the stock muffler).If your looking for better performance, your starting at the wrong end, get a less restrictive muffler and tune the carb to it. The motor has to "breath " out before you can shove more fuel in, we have good results using a HD Dyna muffler with any carb stock or otherwise.