In the absence of a 250 thread posting this here as suggested.
Just got a 1979 250N and it seems to have a flat spot as you open the throttle bike fitted with Motad 2 into 1 exhaust as opposed to stock twin set up.Keep opening the throttle and she gets over the flat spot and pulls ok but I'm sure she should be smoother than this.
Before I strip carbs already have rebuild kits at the ready, has anyone out there any tips or suggestions do I need to rejet?
I've just bought a 1982 CB250N with regular exhausts and it does exactly the same thing. Big hole, then here comes your power. Pretty sure mine is cos it's not set up properly, but just thought I'd let you know it might not have anything to do with the Motad.