Usually new o rings and pressing down hard enough on the carburetor to compress the o ring a little when you install it will fix it. The o ring has to be springy to work, but after a year or two of soaking in methanol they start to harden and need to be replaced. If you want some insurance, a little RTV silicone around the outside gives you some insurance. The machining is fine on Super Tigres from what I can tell, especially in that area.