Real talk here.. I had the 2's on a 421 cub witch worked great!! I switched to the 4's to try something new.. My first thoughts were it gave it more throttle response but it did create a dead lean spot shortly off idle.. I had to make a simple pilot ajustment and it is pretty spot on! Im not claiming that it made a huge power gain or anything.. But however the bike is more responsive!! As windy stated over and over again the 4's require a bit more fuel.. No biggie, just bump up on the pilot!! For 200.00 bucks i think its a good investment!! Fyi,yous can all bash on me!! I enjoy it!!