Starts but dies out immediately.

[Pete-speed]

[have replaced all fuel flow related parts and filters pump, relay etc. bike will start briefly , seconds then dies and successive tries get worse until it sits for awhile. Feels like a fuel starvation problem but got flow through the pump. Anybody have any insights?

[Billy Bananahead]

Longshot, is the side stand kicked down or kill switch engaged?

[Pat Conlon]

"It Starts, runs for seconds, then dies..." ....sounds like a misbehaving fuel pump  or something impeding fuel flow....keeping the carbs fuel bowls from refilling.
Is your tank clean?
Try bypassing the fuel pump and fuel filter. Take them out of the equation.
You need 1/4 tank of fuel to get enough head pressure to gravity feed the carbs.

Welcome to the forum
Try and post in the Intro section, tell us what you're doing.
Modify your profile, In your signature line put in the year FJ you have. That info. will appear automatically so you don't have to remind us.

Cheers. Pat

[Pete-speed]

Side stand switch checked , new fuel pump and fuel pump relay. Checked flow at pump outlet good. Going to replace relay unit ( starting circuit cut off relay), if I can get at it without removing cowling. All thoughts and suggestions are appreciated.

[86FJNJ]

I second Pat's advice to hook up the tank to the carbs without fuel pump and see if it stays running.

[Pete-speed]

Will try direct tank to carbs manana, have checked pump is squirting but can't hurt to try. Let you know, thanks for the feedback.

[red]

Pete,

Is there rust or dirt inside the gastank?  A fuel-line filter would be a good idea generally, and if you already have one, it may be clogged. 
Never know where the PO may have put an in-line fuel filter.  One guy stuffed a filter right into the gas line, which will catch the crud but it clogs up fast because the filter face is so tiny.  Also, there is no way to inspect the "filter" for crud because you can't see the filter at all until you disconnect the fuel line. 
If the carbs have crud in the lines, you may be able to blow them clean from the inside or remove the crud with a strong vacuum on the fuel lines.
Amazon and lots of places have clear glass in-line filters with porous bronze filter elements.  Easy to inspect and re-new the bronze filter element.
Just shooting in the dark, here.

[86FJNJ]

Pat, not to hijack the thread but as I convert my 86 to fuel pump hopefully this weekend I have the regular yamaha fuel filter under the tank but could I add another smaller filter before the fuel pump or after the fuel pump as an extra level of protection for the carbs?

[Pat Conlon]

The oem Yamaha fuel filter goes between the tank petcock and the fuel pump inlet. The filter does a great job catching small rust particles from our old tanks so, no, IMO you don't need anything additional.

If it's that bad, look at electrolysis on the tank and a POR15 or Caswell sealant.

[red]

Pete,
If you find a fuel filter on the fuel line, you can tape a strong little magnet to the side of the filter to catch rust and iron particles. You could also stick a magnet inside the gas tank near the fuel outlet.  Can't hurt, might help. 

[Pete-speed]

Did the direct connect of the fuel lines even though I have strong flow from the tank, 1/3 full and new fuel filter, as well as strong squirt from new fuel pump. Also blew 100 psl air in carb intakes and fuel line to carbs. It now starts for minute but after revs it fades out. Playing the throttle keeps it going at stalling revs. Can all 4 carbs be gummed up?

[Pete-speed]

I have used lots of gumout carb cleaner and Lucas fuel additive because the gas is old. Would bad gas allow bike to rev at all?

[Pat Conlon]

Ethanol laced gas absorbs water. Old ethanol laced gas water fouled crap. New ethanol gas is ok if you don't leave it in Thor fuel bowls.

Don't ask me how I know...

[86FJNJ]

Was bike runnning fine when you parked it or is this a bike you got recently you're trying to get running? If dies early but is ok when more throttle then it might be your pilot circuit. What setting are your fuel mixture screws at?

[red]

Did the direct connect of the fuel lines even though I have strong flow from the tank, 1/3 full and new fuel filter, as well as strong squirt from new fuel pump. Also blew 100 psl air in carb intakes and fuel line to carbs. It now starts for minute but after revs it fades out. Playing the throttle keeps it going at stalling revs. Can all 4 carbs be gummed up?

Pete,
By all means, get rid of any old gas in the FJ gas tank.  If you want to use the old gas, your car can dilute the old gas in the bigger gas tank. I would use top-tier non-ethanol gas for a while, at least.  Run a can of SeaFoam (mixed per label instructions) through the gas tank.  SeaFoam is magic stuff, but not instant magic.  It may take a tank or two of gas with the SeaFoam additive for best results.  Is the choke assembly working properly?