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Hard to tell without seeing things.  You should have a ground wire from frame to back of engine, and another from starter bolt to battery negative.  # 8 and 9 here   https://www.partzilla.com/catalog/honda/atv/2000/trx450es-a-fourtrax-forman-es/battery   You have an N showing on the meter and a strong green light on the N indicator on the meter?

No adjustments that I'm aware of.   @toodeep you have any ideas on this one?

Thank You all for the help.  I was able to remove it and replaced the gear position switch.  But I still can not get my atv to start without jumpering the neutral switch wire to ground.  So far I have replaced the small sensor on the front of the engine and now the gear position switch at the rear.  I am not sure what is wrong.  Now I am wondering if I have a bad ground somewhere on the engine?  

I bought the service manual before I pulled the motor out, but during the re-assembly process I broke the electrical connector off the solenoid assembly B and the solenoid assembly linear so I bought a new ones and installed them. Is there any adjustments that need to be made to the solenoid assembly linear (Picture)?  I also removed the valve body and cleaned it out. Could the clutches be sticking and need to be replacd? 

Ok, that actually makes sense.  You have two clutches in that machine (DCT, Dual Clutch Transmission).   One is for 1,3,5, and the other is for reverse, 2, 4   So, given that you started having this problem when you disassembled and reassembled the engine, I would guess you didn't get something back together right on the 2nd clutch.   That said, first I'd do some testing and make sure that the solenoid on the front of the engine is working properly.  The DCT's run off of oil pressure to engage the clutches.   Go to the toolbar at the top of the page, click on the "service manuals" button, and download the factory service manual for your machine.  We don't have one for a DCT Rubicon, but for your engine troubleshooting the one for the 2014-2019 420 DCT should work fine.   Look in section 13, which will show you how the system operates, and then you'll have to try to figure out what exactly isn't like it should be.   The DCT's are complicated, and a PITA to work on, which is why I got rid of the wife's DCT Rancher when she decided she liked my 05 Rubicon better.