I need a crash bar for my 2002 fatboy will any softail one work ???

Yes they do and of course trailers as well.

Black Harley Softail Hitch: 1984 to 2017 - US Hitch

https://www.ushitch.com > Harley > Softail FLST

Fits the Heritage Softail Classic and Deluxe from 1984 to 2017. Also fits the Fatboy prior to 2007. Includes hardware, removable tow bar and 1 7/8? ball.
US$269.00 · ‎In stock

https://www.google.com/search?q=2007+hd+heritage+softail+trailer+hitch

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Duplicate question already answered

Top view - behind left hand transmission end cover:

http://i40.photobucket.com/albums/e237/jd2694/Fatboy%20Pics/Drain-Plug-1.jpg

Bottom view:

http://i40.photobucket.com/albums/e237/jd2694/Fatboy%20Pics/Drain-Plug-2.jpg

FORMULA+ TRANSMISSION AND PRIMARY CHAIN LUBRICANT

(Part No. 99851-05)

or

SYN3 20W50 OIL (Part No. 99824-03/00QT quart)

http://officialharleyparts.com/wiring_diagrams.php

Hi, Anonymous for this scenario you will need your service manual that has all fastener torque specs -fluid capacities and a wiring diagram on the back pages, parts fiche, and owners manual if you can not find the best tool you ever bought for your Harley, despair not, for a mere zero $0 you can download another one.
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/softail-models/929722-rear-crash-bars-on-a-heritage-need-help.html
http://www.mediafire.com/file/65o6mbkdq5ty8ke/99_to_05_Harley_Softail_Service_Manual.pdf/file
https://partsfinder.onlinemicrofiche.com/ronnies/showmodel.asp?make=hdmc
https://serviceinfo.harley-davidson.com/sip/service/document/6300
https://www.6ya.com/ to speak to me personally

You'll be better off with an OEM manual. You can get one at any dealer or order one online for any dealer.

Try running sea foam a couple of times.