Back wheelconstantly spins

Sounds like your clutch has locked up. Most likely the oil that was in your clutch has gummed up and locked the plates together. Pull the clutch in and try rolling the bike back and forth. If the back wheel spins freely then it may be another issue. If it doesn't move try pushing it forward and back either by sitting on it or by standing astride it. If wheel free's up then you should be able to select gears.

Hi, Jake, the starter clutch is a separate mechanical gear driven component that is activated by the starter motor, it engages the clutch pack ring gear to turn over the engine. It has an internal mechanism that allows the gear to turn in "ONE DIRECTION" only and once the engine starts allows the gear to free spin with engine rotation. If the starter gear free spins in "BOTH DIRECTIONS" then the drive gear has failed, it is not serviceable and needs to be replaced.
For more information about your issue and valuable "FREE" downloads that you will need for viewing or printing please click on the blue links below and for more specific information or questions at no charge please feel free to contact me at [email protected]. Good luck and have a wonderful day.
https://www.hdforums.com/forum/touring-models/1145282-starter-motor-just-spins-and-does-not-engage.html
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https://ownersmanuals2.com/harley-davidson/softail-deuce-2005-owners-manual-66406
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with belt off see if motor free spins .the blower wheel should not free spin with the belt on and entire drum will turn with it otherwise you could have a bad motor and a blower wheel

One of two things has happened. You have a damaged wheel / tire assy. One of the wheels is bent or the tire has a bubble. Or you have a warped brake rotor. Most likely it is a front rotor - but can be any one of the four. To ck for a bad tire wheel assy. Jack up the car each tire one at the time, and spin the tires looking for a out of round side to side motion. Also at the same time you can ck for a warped rotor by spining the wheels and have some one easy step on the brakes if you feel one spin free then lock up then spin free that is the bad rotor. 

Back wheels have a gear that connects to the drive chain. on each side. those spin.
The front ones which are Idlers do not spin as the idler wheel as a bushing in it that allows free motion on the shaft without resistance. Use a nylock nut with Locktight for starters. The try that.

Hope this helps. -Jeff anchorage small engine repair.