What kind of motorcycles are NOT street legal

Dirt bikish? Are you speaking of an Enduro? They actually are street legal. Horrible ride on the road because of their knobby tires, but they were made to go from road to dirt and back again. Otherwise, you can get a metric cruiser with a 250 cc engine. I just did a quick search and saw several 250cc cruisers brand new for less than $2000 (2354 Canadian), so used ones would obviously be a lot cheaper.

In Colorado you need
1)hi/lo headlight
2)tail/brake light
3)license light
4)horn
5)DOT approved tyres
6)MSO, title, or certified VIN inspection and notarized Bill of sale (must be no older than 90 days)

you do not need turn signals or a speedometer

You can make a dirtbike street legal thing is u need to outfit it with headlights, turn signals, speedometer, brake/tail lights. It will then need to be inspected by the license bureau. If it is fit for the road u will then need to safety it & then plate it. You'd also want to put street tires on it so u have better asphalt grip.

With all that labour & parts cost & such u could pick up a good little used SV650 or something for roughly the same as converting over the dirtbike.