I actually sacked my entire band a few weeks back because of this. Basically, I wrote the music, they other guys were just doin it for a laugh. We had a keys player who didnt know the songs after 18 months, A drummer who didnt like anything we were coming up with, a bass player who said "You write It, Ill play it!" and a singer who couldnt sing that well (although I will give him credit for his attitude and dedication, which were top notch!)
Our other guitarist left because it wasnt what he wanted to do. That I can understand, but it got me thinking that I was wasting my time, and since I jacked the band in, two of my friends (including the ex-guitarist) have nabbed me for their new project!
I guess you need to think of where YOU want to be and if youre not there, make the change. If the drummer proves to be a let down, lose him. Harsh I know, but with that lack of dedication, he will only hold you back. I understand he has bought a new cymbal, and thats great. I hope this means he's taking it as seriously as he needs to, but in all honesty, if ANYONE in your band is hindering you, have a word and take the appropriate action.
I hope it works out for you. I know how hard Bands can be. Its expensive and often an uphill struggle, but the first time you walk out on stage, thats all gone. Just be honest with him (sounds like you have already) and keep that honesty. Its too easy to fall out with people in this business, and as Ozzy Osbourne once said....
"You meet a lot of people on the way up. DONT MESS WITH THEM cos you meet them on the way down as well!"