Motorcycle Repair: yamaha maxim 400, rust check, electrical diagnosis

Question
Brand new battery fully charged. It's not electrical to my best knowledge. I have a lot of training in electronics and couldn't find anything wrong. Could it be something internal that I wouldn't know about? I can work on most things short of dropping the engine and tearing it apart.
my email is american1st2fight@yahoo.com
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The text above is a follow-up to ...

-----Question-----
The bike won't start, turn over nothing. The headlight still dims when the ignition button is pushed but nothing happens. I jumped the starter to the battery and it about jumped out of my hand, seems to work. I replaced the Celluloid, starter relay, all the fuses are new. I don't think it's electrical after all that. I talked to another mechanic and he said he could fox it for $800 but didn't tell me what the problem was, except that he would have to drop the engine when I complained about the cost. He was thinking something internal. Any ideas? thank you!
-----Answer-----
Hi Jason,

I suspect the battery is defetive and/or not fully charged. Other electrical problems may be present.

Electrical diagnosis must be performed to determine the integrity of the electrical systems. Testing is done with a fully charged battery in good condition.

Do you have an email address? I return tech files by email. There was no email addy with your question as requested and explaining in my instructions. If you want the files, respond accordingly.

Get a copy of the service manual and follow testing procedures.

Visit Electro Sports website and follow their "Fault Finding Chart."

https://www.electrosport.com/electrosport_fault_finding.html

Respectfully,
Mark Shively

Answer
Jason,

Below are common causes for the problem as described:

Check the starter button contacts for evidence of corrosion and rust.

Check ignition sw positions for continuity.  

Check the SOLENOID for evidence of corrosion, rust, and loose cable connections.

Check battery for evidence of corrosion, rust, and loose cable connections.

Check starter motor brushes length. Replace brushes if worn beyond service limits.

Respectfully,
Mark Shively