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Discussion Starter · #1 ·
01 ZX9r, 15k miles, daily commuter, most maintenance up to date.

On my drive back from work last night the bike showed signs of running low on fuel from main tap. Switched to RES without any change, slowed to a stop and bike dies. Restarted fine, drove normally except for bucking at nearly WOT. Stopped for a refuel to find tank at half full.

Next morning I started the bike normally with choke on full and after warming up, showed signs of fuel starvation. Stopped bike, closed choke and idled fine. Pulled off 100 yards and again showed signs of fuel starving. Shut off the bike and restarted fine, again bucking at nearly WOT, idle stable.

Started bike, used choke at 3/4 for 30 seconds and again showed signs of starvation. The bike will idle all day perfectly, though when given much throttle under load shows bucking.

My thoughts are with a failing fuel pump. Am I correct in the assumption that having the choke on full when warm would drain the bowls very quickly simulating fuel starvation if the pump were not keeping up?

Any thoughts or ideas? I will be dismantling and checking inline fuel filter and checking fuel pump by removing hose from tank tap and checking for vacuum on fuel pump intake line.

Thanks gang!
 

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Checked the fuel filter? The early FI GPz's(81-83?) had a fuel filter before the pump. The pump pressurized the system to 33 PSI at idle and as soon as the throttle sensor moved, the pressure went to 35 PSI.

On your bike, It sounds like it could be several things:

1. Fuel filter clogged.
2. Fuel pump failing.
3. Fuel pump relay failing.

Because your bike has carbs? a low pressure pump is needed to keep up with the demand. Try disconnecting the supply line from the pump, turn on the bike and check for fuel delivery.
 

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Discussion Starter · #4 ·
If my float bowls run dry while crusing, pressing the starter button will activate the fuel pump and fill the bowls back up. Is there some sort of pressure switch between the pump and the float bowls that triggers the pump to activate?

Checked the fuel filter? The early FI GPz's(81-83?) had a fuel filter before the pump. The pump pressurized the system to 33 PSI at idle and as soon as the throttle sensor moved, the pressure went to 35 PSI.

On your bike, It sounds like it could be several things:

1. Fuel filter clogged.
2. Fuel pump failing.
3. Fuel pump relay failing.

Because your bike has carbs? a low pressure pump is needed to keep up with the demand. Try disconnecting the supply line from the pump, turn on the bike and check for fuel delivery.
 

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I've used a very good brand of electrical contact cleaner/preservative on my 82 GPz1100 B2's for many years called "De-oxit" caig.com - Home of DeoxIT - CAIG Laboratories, Inc. is their website.

It can be purchased at Radio Shack in the U.S. and any other electronic supply stores. I use it on my bike's electrical connectors, my home cordless phone's charging cradle's and my home entertainment centers audio patch cables.
 
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