Just bought a new 66cc engine kit. This is my second 66cc, and it is on the same bike my old one was on. Ive only ridden it for about an hour or so in total and while it runs, it does so in a slight jerking motion. This jerking motion gives me the impression that it wants to go faster, but it doesn't have the power. Is this common for an engine still in it's run in period? I cant remember if my old one used to do the same. Both had been slower during run in period, but the slight jerking I'm not too sure.