My friend Brock has a 1995 Tomos Targa moped. He really doesn't treat it that well and I usually do most of the maintance for it. It has 6600km on it and a brand new hunter exhaust, 31tooth front sproket, and new carb. For some reason it takes a long time to warm up. When I am driving next to him it accelerates then studders and so on till it has hit top speed. He always drives it full throttle around town unlike me. I am thinking he needs to replace the top end, but what do you guys think?