After being frustrated for almost 2 years with my sons TTR125 and not being able to get it to run well without back firing, iratic idle and running hot, I bit the bullett and bought a new Mikuni VM24 carby for it. I could not find much info about what carby would fit and what other mods would be needed apart from the BBR kit which at $299 seemed a bit excesive. So I took a punt and went for the VM24 and hoped it would work. Much to my delight the carby fitted straight on using all the standard parts, with the only mod needed was to drill the top of the Carby cap where the cable goes in slightly larger to allow the standard TTR cable to fit through. I installed the carby with the standard jets that came with it Pilot 17.5, Main 97.5 needle I moved from 2nd clip to 3rd (middle) and air srcew at 1&1/4 turns out. The bike started easier than ever, idled smoothly and ran crisp and clean, all without any further adjustments! Ive never been able to acheive this with the standard carby despite spending countless hours and lots of money on jets, needles seals and gaskets. My son is very happy and said it has heaps more power. Every thing fits well and the only negative is the airscrew is hard to reach when the carby is mounted, but only takes a few minutes to remove carby to adjust. It is running that well I dont think Ill need to change it often anyway. Im going to buy another TTR125 for my other son soon and a VM 24 will be the first thing I do to it!