How do I remove the gas tank on 2004 polaris sportsman 400 atv.

Question edited for clarity.
Question moved to a Polaris Category.

Normally, you would just drain the tank, remove the fitting and replace the gasket. I don't see a gasket though, unless it is just a standard O-ring. That is the way to do it though.

https://www.google.com/search?q=1999+polaris+sportsman+500+fuel+tank+gasket

https://www.google.com/search?q=1999+polaris+sportsman+500+fuel+tank+leaking+from+bottom

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Page 85 of the Owner Manual for Fuses. It also says it has a circuit breaker, but doesn't say where?

https://cdn.polarisindustries.com/polaris/common/parts-manuals/9923420r01_lo_res.pdf

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137 pages

Various ideas in the link.

Engines only need three things

Good fresh fuel to the engine.
A spark at the right time
Compression

https://www.google.com/search?q=2004+Polaris+Sportsman+700.+Crank+but+no+start

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https://www.youtube.com/watch?v=FEsDt7WJrcA
https://www.polarisatvforums.com/forums/atv-repair-maintenance/36119-wont-start-checklist.html
https://atvconnection.com/forums/polaris-ask-expert-fond-memory-old-polaris-tech/364256-05-polaris-sportsman-500-ecm-issue.html

check cap vent -fuel filter - valve - carb problem

You might try to ask someone to help on the ATV web site below:

https://atvconnection.com/forums/polaris/330956-year-my-sportsman-400-4x4-1997-a.html

You can check a solenoid by using an ohm meter. Or just take it to a auto shop and ask them to check it for you if you don't have one. They can check it real quick and shouldn't charge you anything.

It appears that you have fuel venting problem or a float level set too high. Check the entire fuel system for kinked / blocked fuel lines/ filters and check the float level or fuel manifold pressure if it has one.

you probably dont have a fuel pump issue, atv's after sitting have a problem of not starting due to carb gumming up. if its fuel injected, then i would say poss fuel pump but if not, the carb gummed is more than likey the issue.

If you need further help, reach me via phone at https://www.6ya.com/expert/allen_b068623c5003aa4b

If your atv has been sitting this long, the carb is probably stopped up internally... take the carb to a qualified professional and have it cleaned and set...(take a few pictures so you know where all the hoses re-attach)

ALL it takes for an engine to run is:
1. A timed spark
2. Adequate compression
3. Proper fuel/air ratio delivered