my 94 has fuel, has spark but will not start.  I have tried carburator cleaner, and starter fluid, but it won't start.  a brand new battery, and it spins it over nice and fast, so what gives.  new spark plugs too. 
oh and it only has 2589 miles, so I'm pretty sure it isn't the valves.
bike hadn't been ridden in a long time, then I bought it, cleaned the carbs and put a couple hundred miles on it.
thanks in advance

If the carbs were very bad when you cleaned them there is a great chance that they got more gummed up after your couple rides. I would pull em and check again... Did you give a thurough cleaning? take them all the way appart?

yeah, I took them back apart, and they were still spotless.  I spray starting fluid in, but it won't start.  even though it has spark.

Jeremy,

This is a frequently asked about problem here, you can find a lot of relevant posts by searching.  We need more details about what your bike is doing - are you getting the clicking from the relay for instance?  I am going through that myself right now, just ordered a new relay online.  (If you are getting clicking but not firing up your relay may be bad.)  It could also be vacuum related, lines may be blocked.  Also, it could be your battery even though you said it is new, cold weather can kill it.  There are many posts about battery tenders, get one and hook it up if you haven't already (I have new battery but need it hooked up to tender now and hell I am in Houston.)

Very helpful people here, look for some of there past comments and eliminate the possibilities one by one - that is what I am doing at the moment on mine.  Oh, and drinking beer while you work on bike helps for lack of patience

Pete

Like houston said, do a search. But just my $0.02, you said you are getting a spark but do you know if it is a strong spark? I believe in one of the threads about a bike starting hard Kerry mentions something about checking spark strength. May want to look at that before going to far, may be a bad coil or loose connection somewhere. Good luck, hope you get it fixed up and back on the road soon.

Same problem just this morning - spark yes, fuel yes, air yes -  but just would not fire.  Turns out I had misadjusted the throttle cable last night - just a small amount, but apparently doesn't take much open throttle and a cold engine just won't fire, even with full choke.  Finicky little beasties.

well I think I figured it out.........put in new plugs, and it started right up.  it's running better now than it ever has.  strange though, cause I only put 300 miles on the old set, but they seemed to have plenty of spark when I pulled them out and cranked it. 
so in sumation: 
    motor would crank but not start
    had spark but didn't start
    carbs had just been cleaned
    new battery with full charge
    turned out to be the spark plugs

hope it helps someone out

thanks for all the ideas

You cheated  You said it had "new plugs" If you hadnt said that I bet one of the first responses would have said plugs 

well, isn't 300 miles still new?  lol