CB200's are one of those bikes that the throttle cable has to be routed exactly right on, no leeway at all.
If you need photos, let me know.
I've experienced your problem - everything looks/acts fine, then you put the tank on and it instantly redlines when you start it up, yeah??
Also, when you bolt the carbs to the head, you have to do it very evenly, one side of the carb to the other.
There's a rubber o-ring on the manifold that deforms if you don't do it evenly, allowing big-time air leaks.
Don't ask how I know all this..............been there, done it.