This is continuation from my out post in August. I opened the fuel pump and found that the lower rubber check valve was in pieces and thought that surely was my problem. I bought and installed a new fuel pump. I the problem is still there. I can not believe there was no change do to the condition of the fuel pump. I checked all the connections, changed tanks and hoses, disassembled and cleaned the carbs. The engine starts and runs great until I go to WOT, after 100yrds or so it falls flat and starts surging. I can push the key priming pump and it will try to run right. It is as if it is running on one cyl. Do the check valves each supply a carb or both? If each which valve supplies which carb. I think part of the destroyed valve my be stuck somewhere in s carb.