ok so me and my buddy have a lb50 yamaha chappy we are fixing up. basically no parts or anything were damaged when he rode it two years ago. he just got it real dirty running it through the dirt and mud. so i figured it just needed to be cleaned. after putting fresh gas and new oil in, we let it idle for a while and sprayed choke and carb cleaner in the carb and it started running a lot better. within an hour we finally got it to run and go about 25mph. but it used to go 40-45mph when he used to drive it two years ago. my guess is the carb is dirty and shit needs to be cleaned is this right? but what else could be keeping it from running at top speed of 45mph?