John Deere 425 Start Up

Recently having problems with the JD425 start up. When starting the engine, a lot of smoke and some fuel is emitted from the exhaust pipe. I have to work the throttle to keep the engine running and cannot mow with this much smoke being emitted. Alone, I can't check the air-fuel adjustment since I have to work the throttle. Put in new plugs with no effect.
Ideas?

You have a carburettor problem.
The float valve is not cutting off the fuel.
If you check the oil better than average chance is you will find it over full.

Do not run the engine like this you will accelerate wear and could even do serious damage.

Start by overhauling the carb the instructions are here http://outdoorpowerinfo.com
When you have done that , drain the oil and replace it.
Run the engine for 10 minutes or so then drain the oil, a second time replacing both it & the filter.