Who did you buy the bike from? You'll need to do your damndest to track them down and get a notarized bill of sale, if you don't have one already. You've got the VIN check so that's good; any other states that it's been registered in that you know of? For instance, mine has New Jersey tags and reg. stickers from 1984; this was noted on the VIN check so I knew they'd ask about it. I sent off to NJ for a title check ($15) and it came back with no results. Get that done for every other state you know about; if none, don't worry about it.
Here's the link to the checklist of stuff that the state wants to see.
http://www.colorado.gov/cs/Satellit...goBlobs&blobwhere=1251600297275&ssbinary=true
Follow this like the gospel; they don't put things in there just for the hell of it. As I recall, this is everything I gave them:
VIN verification (Adams County State Patrol office)
Statement of Fact (why I was applying for title)
Notarized Bill of Sale (I bought the bike mostly complete from Steele's, and Brandon Steele's mom is a notary, so I just had to hassle him for that and we did it almost a year after I bought the bike)
Title record search from Colorado, using both 2F0 and 2FO just in case - no results found
Title record search from New Jersey - no results found
Application for Title form
Pretty sure that was it. Go over the form I linked, maybe even take it down to your local DMV and get their input, and it might be worthwhile to talk to the state office if you still have questions. Feel free to ask anything else.