Moen kitchen faucet model 7730 handle problems

Hello,
I had a leak in the handle. I replaced the 1225 cartridge, and it no longer leaks, however when you turn on the water, the handle drops on it's own now and won't stay on. I've checked the diagram and have all the parts replaced properly.. I'm pretty sure. Is there another parts kit that I need to install? How can I fix this?
Paul

The new cartridges have alot of lubricant on them, try pulling it out and wiping some (not all) of it off. Also did you replace the small metal washer ontop of the stem? This can cause the same problem if not installed.