I do understand that it is a new carb. I dont think that necassarily garuntees that the diapram is set right. also i got no way of knowing that your actually set to 28 deg. al i can do is take your word for it. I dont know if the best timming is variable per engine so i was asking someone that has set up way more of them than I as i have only set up one and it ran spot on at 28 degree. I am very certian i have or should say had before it crapped out, mine set precicely at 28 degrees.