also looks like a single reed valve.
im trying to get a two petal on there with an 18 phbg and a malossi variator... maybe dual stage reeds? should put it into the high 40s maybe low 50s?
this kit shouldnt really be putting that much power out at low rpms like you are saying... maybe your variator is just set up for low gearing? also the 15 probably likes lower rpms more than most carbs people are gonna be putting on there.
what kind of pipes are people gonna use? im trying to decide on what i should get... something high end.