Girls show intrest when I meet then and I number close them quite quickly but when I talk to them and mention day 2s they say sure then a few days before the day 2 they flake with some lame excuse.

How am I ment to keep their intrest so they want to To go on a day 2 with me??

Don't number close quickly.

A nice thing to do is for example mention the day2 during the talk BUT don't invite them right away, for example "I'll go to have coffee at this place, it's supposed to be one of the best coffee in town".
Then, afeter some time you say something like "I have to go to meet my friend, but you're cool, give me your number and I might call you for that coffee I mentioned earlier".

This work very nicely if the day2 is a house party you're (eventually) having in your house

Then keep talikng to her for few minutes after the number close (this shows you're not there just to get her number)

Sounds like maybe you're not actually generating enough interest to begin with, and they are just giving the number out to 'be nice' or to not have to deal with the awkwardness of telling you no. Even if they are attracted, they may think back and wonder why you are interested in them, what your intentions are. Are you qualifying? Qualification is very important so that the girl has a clear reason why you are interested in her. Be sure to learn something about her and tell her why you like her or find her interesting. This has to be something -other than her looks-! Look up qualification if you aren't familiar with the concept. I particularly like what Sinn and AFC Adam have to say on the subject. Also, are you setting the date for something specific when you get the number? Try getting her excited about a particular place to meet, or a particular event, rather than just 'going out sometime'.