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Discussion Starter #1
I have a 2001 CBR600 F4i with 54,000 miles. She was running rich for a bit this afternoon (according to a friend riding behind me) then started sputtering bad on my way home tonight. Idles beautifully, revs just fine with no load, but with load it barely gets past 8k RPMS, the spray bottle test says that the #3 cylinder isn't firing. It's getting plenty of fuel, as when it sputters and pops the extra fuel shoots flames out of the exhaust, and the oil is full of gasoline. I've got a few theories, but I haven't started tearing her apart yet. What do you guys think? Spark plugs were replaced over the winter.

My theories so far are:

Spark:
Either spark plug wire or ignition coil causing issue

Fuel: Injector stuck open, fuel pressure regulator issue?

Or top end rebuild necessary, due to:
Burnt valves or no compression.

I'd love to hear opinions as to which of these seem most likely, and if I've missed any options.

Thanks!
Patrick
 

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Discussion Starter #3
That's what I'm leaning towards as well. If an injector was stuck open, it likely wouldn't idle properly, correct?
 

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Move the plug to another cyl and see what happens I wouldn't run it too long with gas in the oil before you change it. (oil)
 

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Discussion Starter #5
My current plan is to pull it apart, check the wires and obvious stuff like that, do a quick compression test, then swap the coils and wires to a different cylinder and see if the problem moves. If that doesn't fix it, I'll move the injector from that cylinder and see if that moves the problem. Do you think it would be safe to do all that before changing the oil, or would it be safer to change the oil first and hope I don't contaminate it again?
 

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Oil is cheap compared to bearings and other engine parts.
 

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Discussion Starter #8
Aha, after further search of F4i forums, I think it is the fuel pressure regulator. I should know for sure in 2 days when I get the part in. They're apparently known for failing on the F4is, and cause the exact symptoms I've experienced. I'll post back when I know for sure.
 

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Aha, after further search of F4i forums, I think it is the fuel pressure regulator. I should know for sure in 2 days when I get the part in. They're apparently known for failing on the F4is, and cause the exact symptoms I've experienced. I'll post back when I know for sure.
Sorry, I was asleep at the wheel. That was the problem with a guys bike at the track last year. Another guy with the same type of bike helped him out.

Unkle Crusty
 

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Discussion Starter #10
Oh, no worries. Hopefully that's all it is...I'm fairly optimistic about it. I should have the new part in 48 hours, which will give me time to swap my (ridiculously pricey) spark plugs and change the oil. I'll let you guys know how it turns out - thanks for the input so far!
 

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Discussion Starter #11
Forgot to update this - sorry guys! Turns out it was a damaged wire from the ECU that controls the #3 injector.
 
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