Does it Bog briefly, then pick up, if so, it is probably the Low speed needle. Try to lean the Low speed a little, and see if that helps.

Another way to check the LSN, is to pinch off the fuel line about 1 inch from where it enters the carb. Count the seconds till the engine dies. The RPM's should raise slightly, and the engine die around 3 seconds. If it dies under 3 seconds, the LSN is too lean. If it stays running much more than 4 seconds, LSN is too rich. From there, you should be able to run the engine up to temp, and check your High Speed settings.

I know some people don't like the "pinch test", but I have had good results. It helps get the engine in a decent running tune, so it is easier to fine tune.