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Discussion Starter #1
I am having some troubles with my 2003 R1. First off, mods include PC-V, and Spark Arrestor Exhaust. EXUP, Headers, and filters are all stock. Bike has 27k miles on it and had been sitting for a couple years before this.

Now what it does. First, it doesn't start up right away. Turns over great but doesn't fire off. I can smell it getting rich. I sit there and switch between cycling the initial fuel priming and trying to start it for about a minute until it will pop off. Then, I can't tell when it does it, but sometimes, it will be real snappy with the throttle and seem to behave normally, and others it will be real laggy and then take a couple seconds to wind down again from snapping the throttle. Then, if I take it for a ride, it will ride pretty good for about a minute until slowly losing power. It gets weaker and weaker and will eventually die. If I turn it off and on again, it will get up and go for about another 30 seconds before same result. If I have it sitting there idling, the idle will get weaker and weaker and weaker until it dies over the course of 2-3 minutes.

Actions taken so far: Cleaned the tank, new fuel pump, new plugs, cleaned injectors, lots and lots of seafoam, come carb cleaner through the throttle bodies, different tunes (and stock again), blowing out all the fuel lines, checked synchronization (maybe low vacuum, all similar values), and checked charging voltage.

Next steps, check compression and new coils.

If anyone would have any other suggestions or inputs, I would appreciate it. Can post a video of the bike running and dying if needed.
 

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Discussion Starter #2
So after some more diagnosing, compression is good, new coils, throttle bodies synced with good values of vacuum. Now on to the strange part. When the bike was tore apart for the synchronization, I had the air box off, and the bike ran fine for 15-20 minutes. After that was all done, I put everything back together, and I'm back to the bike running and slowly dying. My next thought was if they fuel pressure regulator is bad or out of spec. Anyone have any experience with this? Would really appreciate the help.
 

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Going by your update , sounds more like you might have a blockage in the intake tract or the filter is not flowing air. Try replacing the element with a new OEM one
 

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bad fuel pressure regulator or stuck injector (because bike sit unused for too long)

think like this: injector not clogged, it stuck open
 

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Discussion Starter #5
So I thought that also, but I tried running it without the filter even in there and it still ran terrible and died. And when I was cleaning the injectors, they clicked open and closed just fine. Used the diagnostics and they all sounded fine.
 

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ok then pressure regulator

you run engine with airfilter off ? no mice in air ducts

on car engine i would also suspect a coolant sensor
 

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Discussion Starter #8
After talking with a local mechanic as well, I have decided to try a new fuel pressure regulator. Next question is does anyone have any idea where I can find one? All the big parts sites are all saying they are sold out or not available. No one in the area has any parts bikes laying around either.
 

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Discussion Starter #9
Okay. Threw a fuel regulator from an 04 R1 on there. Same scenario. Well if I unplug the vacuum line, the bike idles just fine, but doesn't have any snap to the throttle, but will idle up if I go slow. No pressure means more fuel according to the manual. So could that mean I have too much vacuum? I had tried multiple maps on the bike, all with the same results. Thoughts?
 

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Discussion Starter #11
Radiator and coolant temp sensor all good. Does anyone know where I can find a freaking fuel pressure regulator for this 2003 R1? I cannot find one anywhere. That is my next best guess. I don't know what else it could be.
 

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Discussion Starter #14
Actually discontinued 🥺. So if anyone knows of a used one somewhere that is good, would be much appreciated.
 
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