What I learned was that you need to buy a $27.50 Form 551 or "DOR-551" which can be obtained from a DOR office. Once you have filled out the form and met the requirements of the form, you can schedule an inspection with the Hwy Patrol. There is no fee for the inspection.
If the Hwy Patrol says the motorcycle is OK, then they will issue you some kind of paperwork that says you are OK. (If the motorcycle is home made or otherwise does not have a VIN, they will create and attach a VIN plate.)
Then you can go get the standard vehicle inspection from any motorcycle dealer, then go to the tag office to get your tag.
Now I can't find the email reply that confirmed this, but I believe the Hwy Patrol told me that the motorcycle needs a dual filament headlight and a tail light. You need a working brake light. You need a horn, and at least a left hand mirror. The MO law does not require turn-signals, but if you have turn-signals, they must work.
If your bike requires a conversion kit--KEEP YOUR RECEIPTS. Apparently you need some kind of proof of the conversion.
I've NOT gone through the process and I've heard everything from "I just walked into the tag office and they issued me a tag for my dirt-bike without any questions" to "The inspector said there was no way to make my off-road only motorcycle street legal. It cannot be done." So I think like most government operations, a lot simply depends on the people you end up dealing with. It's probably a crap-shoot.
For this reason, I refuse to buy a non street-legal motorcycle without being 100% content with the prospect that it may never be street-legal.
Also, from reports I've heard, apparently the fact that an off-road motorcycle is already tagged in another state has no bearing on the process in your own state.
I've even heard of states coming back after the fact and revoking a tag.
This contact info may come in handy--it's who I talked with:
Public Information and Education Division
Missouri State Highway Patrol
Hwy Patrol wrote:Conversions of "Off-highway" vehicles must utilize approved conversion kits from the vehicle manufacturer or after-market providers. Proof of purchase and installation of one of these kits is required for the DOR-551 examination conducted by the Missouri State Highway. The DOR-551 form may be obtained from a local DOR contract (fee) office for $27.50, there is no charge for the patrol's examination.
Any further information regarding this matter, may be obtained by
contacting the Motor Vehicle Inspection Unit, Troop A, Lee's Summit, at
telephone 816-622-0717 or 0719.