Do you hear it shift once it gets going? If not, it could be stuck in 2nd, but mine did that and the performance wasnt bad enough to think it wasnt running right? Was still fast, just a little slow off the start.. But you could check it visually, to make sure the little arm on the clutch isnt sticking out. Or prop it up on a stand of somekind and run it with the wheels off the ground.. If it still bogs it's the tune, if it acts right with the wheels off the ground it's probably in 2nd gear.. Truth be told, I never did find out why mine would stick in 2nd.. I'd "look" at the clutch and it would look fine, I'd take it apart and it'd all be fine, then I'd put it back together and it'd shift for about a tank of fuel, then stick in 2nd again.. I ended up getting the single speed tranny and clutchbell.. Still fast and no shifting issues.. But anyway, try and do the pinch test to check you LSN.. If it takes longer than 2-3 seconds, and revs excessively before it dies, you LSN is too rich.. It should rev slightly and die within 2 seconds, when ya pinch the fuel line that enters the carb.. If it's hard to start after leaning the LSN, you should try a hair dryer or heat gun to prewarm the block and head, before tryin to start it.. (and make sure the carb is primed) Let us know what happens and we'll get to the bottom of it!

BTW, I think you can get an HPI 2 speed clutchbell for it, but not sure what the teeth options are.. But I wouldnt do that unless your sure the 2 speed tranny is working properly to begin with.. </p>