dead spot

I have a 1980 KZ1000 LTD with the stock Mikuni carbs. The carbs are jetted with #105 jets. I had a problem similar to another post where one plug was blackened and the other three looked fine. Syncronising the carbs seemed to solve the problem however when I snap open the throttle fully I get a dead spot and the bike stalls but does not quit. If I let off of the throttle slightly I get the power back. If I roll on the throttle gradually or crack it open just short of fully open it goes fine. Any ideas or suggestions would be appreciated.

You have described a condition where the airspeed is too low when the throttle is wide open for the air jets to correct... usually on carbs with replaceable air jets, you would just go down in size on the air jets to correct. You can't do this so...

What airbox and pipes are you using. Are your carburetors VM28SS with the accelerator pump? Have you checked the accelerator pump to ensure it is working? What pilot jets are you using? If you have all stock jetting and the pump isn't working, you can either fix that problem or use larger pilot jets which might help.

The stock airbox and oem air filter is being used. Yes the carbs have the accelerator pump on them. I do know that the outlets for the pump are clear. I thought that the pump was working. I'll have to check that to be sure.

Pull off the airbox hose that connects #4 carb venturi to the airbox. Pump the throttle and check to see if you can see gas coming out the pump squirter in the #4 venturi. The #4 pump squirter is least likely to work as it is farthest from the pump. This is if you are sure that all other squirter nozzles are clear and able to atomize gas.