HI all. I have a John Deere JE75. It starts fine, but when I go to engage the blade the engine bogs down and shuts off. Then when I try to start it again, I am not able to pull the cord. In order to be able to pull the cord again I have to take the top cover off pull it all out and put it back together. Then after it starts and the blade is engage it dies again...Any Ideas??