Sure, after each use you take it all apart for washing, but have you cleaned the actually juicer?
Don't stress, it's easy and takes a few seconds.
With your machine ready to go, combine 3 cups of Water with 1 cup of White Vinegar. Set machine to low and slowly pour the mixture down the chute. Be careful, the water could shoot back up. Turn off the machine, empty the pitcher and repeat again with Water only.
This doesn't need to be done with each use, but it wouldn't hurt either.
P.S. This trick works well for your coffee pot too! Just run the same Water/White Vinegar concoction through one cycle and chase with pure Water for another cycle.