Rode the old z today. It has a flat spot in the power band on low gears. Kinda like a two stroke. Tried cleaning the carb but it didn't work . Has any one a clue why this is happening.

 

try cleaning the petcock and a new gas filter if it has one
and change the spark plug if it hasnt been done in a while

 

A flat spot would not only pertain to some gears and not others. You are experiencing a flat spot at a certain RPM, which would be felt at any gear. My guess is the jetting, and assuming bottom end, the pilot or needle is most likely your problem. What are the current jetting specs?

 

By "flat spot" do you mean that the power doesn't build linearly, or is it a bog? Might be jetting. Play with the fuel mixture screw. Usually it should be around 3.5 turns out.

 

I had a flat/dead spot on my Z aroutd 1/4 throttle after installing a dynojet needle. After trying different clip settings I found it was too rich. I changed back to the stock needle and it runs great.

 

Well, I ruled out the jetting issue because I have been riding it for a year with this same jetting. Could it have anything to do with my valves.