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Discussion Starter #1
I have a 2003 GSXR 750 with 33k miles that a previous owner swapped in a 600 engine of unknown mileage. If I roll into the throttle in 1st gear it will rev out to 14.5k rpm. If I give it a quick hit it bogs around 11.5-12k rpm. In higher gears it is more prevalent.

I have replaced the fuel filter strainer, tried another used fuel pump which did the same thing. Changed the spark plugs and bypassed the kickstand cutoff. I did a fuel flow test and got approx 450ml in 10 seconds which the shop manual calls for 168ml or higher. I dont have the equipment to do a pressure test on the system.

Please help steer me toward some possible solutions or things to check for. I am at my wits end with this bike.
 

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So if you whack it open at 3000rpm say and keep it wide open, it won't go past 12k, but if you slowly roll it wide open at 3000rpm it will reach the rev limiter?
 

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Definitely isnt a kinked fuel line. I have a shop about 45 minutes away that will clean and flow test the injectors for $80. That is definitely on my list of things to try.
 

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I would find the exact behavior I have described and you have confirmed hard to explain. The thing is that the rate of throttle opening (whacking vs. rolling) when starting to accelerate at 3000rpm, shouldn't generally affect engine performance later at 12000 rpm. There are only two ways in which I could explain something like this. Either something is wrong with your STVA and whacking the primary throttle causes it to stick, which I find hard to believe and would throw an error anyway, or you're simply not opening the throttle all the way when you're whacking it. I can't think of anything else, be it a control strategy in the ECU or a mechanical issue that would explain different engine performance at steady state (i.e. after you've reached your final throttle opening and kept it there for a while) based on how you opened the throttle.

I'm therefore more inclined to assume that the particulars of the problem haven't been made entirely clear and something more mundane, along the lines of what Bill suggests, is the cause.
 

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I have had similar problem and tried tested almost everything and no luck till I finally had enough and took it to a tune shop and it turned out the cat collapsed and engine could not breath, hope this helps
 
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