zrider1970

I have just put my xs400 back together and the problem I thought I would have solved by cleaning the carb is still there. What is happening is that from idle to about 3500rpm to 4000rpm it has no power whats so ever and once it pass 4000rpm it is fine. None of the jets where plugged or damaged. The bike idles pretty well but I cannot figure this one out. Does anyone have any suggests? Thanks inadvance. Stu