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I’ve got an 03 gsxr600 engine in my cart.. sort of a cross kart. it’s stock except custom headers, and air intake pods.

I replaced the fuel pump and spark plugs after first riding the cart because it didn’t seem to get enough fuel. The cart ran just fine at idle and would rev all the way out, but while riding, it would run fine at low rpms and not much throttle. Under 50% or more throttle, it would almost completely bog down and fall flat on its face.

This last week I replaced the plugs again, because the engine wouldn’t start (plugs were fouled) they were NGK cr9e. I went a step hotter and got cr8eix. Started right up and again ran just fine at idle and would rev out fully. When riding, the cart accelerates and runs good even under full throttle, but it falls off after about 10k rpm.

Anything under 10k rpm or so is fine but over 10k rpm acts like it’s not getting enough fuel?! The fuel pressure regulator screw is all the way open, i’ve moved it all around and it seems to run best when fully open. Im not sure and never owned a gsxr or similar bike before. Any help or suggestions is much appreciated! Thank you! Don’t worry, i’m going to paint it.
576515
 

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03 GSXR 600z
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Vacuum Lines and fuel pump! I was getting symptoms all over the board from potential timing chain to valve timing to gearbox prolems. Finally got it narrowed down to multiple fuel system problems:
1) Fuel filter & Pump: At higher RPM boggs, it's not getting enough fuel. Take your fuel pump assembly out & disassemble completely. Blow out the plastic housing that encases the fuel pump & reassemble. This solved my RPM bogging issues (mine bogged at 7k RPM). I did a rebuild off of a crashed bike, so plenty of debris in the tank to get rid of.
2) Vacuum lines. Once my bogging problem was solved, it nearly flipped the symptoms to running great at 5k+ RPMs and complete garbage below that, which indicated TOO MUCH fuel. I've read people desribe their bike doing a "Herky Jerky" ...and that's what I'd best describe it as. Anyhow, Pulled apart the air filter housing down to the throttle body assemblies and started tracing vacuum hoses. Sure enough, a TINY hose for the Air Intake Pressure Sensor had pulled loose, so it was drowning the engine in fuel. Popped the hose on and watched it roll coal for about 20 seconds.. good as new. Long story short, apparently when I changed the spark plugs initially, that's when the vacuum hose pulled loose. Bonehead move on my part, but at least it only cost me a set of spark plugs and a fuel pressure relief valve.
 

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Registered
03 GSXR 600z
Joined
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2 Posts
Vacuum Lines and fuel pump! I was getting symptoms all over the board from potential timing chain to valve timing to gearbox prolems. Finally got it narrowed down to multiple fuel system problems:
1) Fuel filter & Pump: At higher RPM boggs, it's not getting enough fuel. Take your fuel pump assembly out & disassemble completely. Blow out the plastic housing that encases the fuel pump & reassemble. This solved my RPM bogging issues (mine bogged at 7k RPM). I did a rebuild off of a crashed bike, so plenty of debris in the tank to get rid of.
2) Vacuum lines. Once my bogging problem was solved, it nearly flipped the symptoms to running great at 5k+ RPMs and complete garbage below that, which indicated TOO MUCH fuel. I've read people desribe their bike doing a "Herky Jerky" ...and that's what I'd best describe it as. Anyhow, Pulled apart the air filter housing down to the throttle body assemblies and started tracing vacuum hoses. Sure enough, a TINY hose for the Air Intake Pressure Sensor had pulled loose, so it was drowning the engine in fuel. Popped the hose on and watched it roll coal for about 20 seconds.. good as new. Long story short, apparently when I changed the spark plugs initially, that's when the vacuum hose pulled loose. Bonehead move on my part, but at least it only cost me a set of spark plugs and a fuel pressure relief valve.
 
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