[bcj]

Most motorcycles with an in-tank fuel pump publish Gallons-Per-Minute rate in the repair manual.

Disconnect the fuel line and route it to a holding can.
Apply a known voltage to the fuel pump and it should move X amount of fuel in Y minutes.
Then you know if it's the pump and filter or something else.

Also gets fuel out of the tank in the mean time and don't have to break into the tank.
There should be specs for this available somewhere.

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Looks like the 86 manual only wants you to use an in-line pressure gauge and Techstream.
Bleah.