Re: what are some of the best mods to do?
It would help if we knew what engine and carburetor you have. 2 stroke or 4?
If a Chinese 2 stroke, in-frame kit then my suggestion first of all would be to give it some time. They don't break in over night. It will take a minimum of 200, preferably 300 miles to seat the rings and get the compression up to where it's supposed to be. They are like a good wine; they get better with age (miles).
As far as carburetion, again if we're talking about a Chinese 2 stroke, what carb did you get? The CNS is notorious for being hard to tune but those who have mastered it swear by it. The venerable NT is hard to beat on an engine in a stock configuration.
Again, if a 2 stroke, an expansion chamber exhaust will give you a noticable performance increase but don't expect motorcycle performance. It is a motorized bicycle and 25 to 30mph is about normal. How fast do expect to ride?
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