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Discussion Starter #1
05 15,000 miles, pc3 full Akro exhaust, not extremely abused bike. Started with a small miss/ studder at a stop light. Had got gas 15 miles earlier, thought it may be bad gas. Put new tank of fresh fuel, and it seemed worse. about half mile of riding it was missing and stuttering. Replaced plugs. Originals were little dark but not fowled. Rode with new plugs, miss seemed gone but under full throttle even in first and second there isn't much power. Will accelerate but not fast. Still thinking fuel issue I pulled pump, checked screen and it was clean. Softly blew out pump filter. Pressure is 44psi at prime and holds at 41psi. 44psi while running. When I pulled plugs I checked stick coils when I replaced plugs and both values were in spec.. Could it be a stick coil or throttle body. Anyone have this problem ? It starts good, idle seems ok but a little rough at part throttle (in shop not on road), revs quickly (again in shop not on the road).
 

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Discussion Starter #3
The fuel pressure under load is 44psi. I haven't checked the a/f ratio. Since I was riding the whole day and the problem started at a stop light I didn't figure any a/f ratio adjustments could have changed.
 

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what spaz said. coil will produce misfire, if pulling smoothley to redline, just down on power, fuel pump or clogged internal filter, most likely pump. pumps can become erratic in performance when failing and unable to maintain pressure necessary for high rpm fueling.
 

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Discussion Starter #5
Fuel pump is definitely not clogged. The pump held 44psi while running and with revs while on a stand. I guess it could be a fuel pump but the pressure stays steady. As for coils, seems that would be more of the answer to me since there is a slight miss. Ok what exactly is the AFR's ? I thought that meant air fuel ratio. I can find nothing in the factory service manual on how to check them.
 

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sounds as if u ck'd external sock filter, not the filter that causes problems. the whole plastic cannister ur fuel pump is plugged into is the main filter. have to remove the fuel pump to ck it. fuel pressure at idle, fuel pressure at low throttle position with increased revs, or whacking wide open momentarily on stand is no indication fuel pressure is adequate or constant on road under full throttle load required for accleration. do a search on here, ur problem/solution covered many times.
 

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Discussion Starter #7
I stated in my original post I cleaned screen and blew out pump filter. I completely tore pump assembly down. Issue definitely isn't a dirty filter. You're right tho pump pressure could vary from bike on stand and bike under load. I'm ordering stick coils and a pump and starting there.
 

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I stated in my original post I cleaned screen and blew out pump filter. I completely tore pump assembly down. Issue definitely isn't a dirty filter. You're right tho pump pressure could vary from bike on stand and bike under load. I'm ordering stick coils and a pump and starting there.
Not trying to be rude, but it seems like you don't know how these pumps work. The pre-pump sock/screen is indeed easy to clean, but the post pump filter is sealed into the plastic housing and is nearly impossible to remove and clean (if you've somehow done this I'd love to see pictures). Blowing air through it will not clean it... it will just move the restriction around. Flow testing a pump assembly at pressure will tell the tale, and I recommend you do that; it's not particularly difficult.

Second, free revving it on the stand is not "under load". Under load is 2nd gear or higher, 100% throttle, above 10K rpm or so.... trust me when I say there is a LOT more fuel demand there than in neutral on the stand. If you do not have a way to display or log fuel pressure "under load", an AFR readout (again) 'under load" will go lean if the pump is having a hard time (IE, fuel pressure dropping). They can drop pressure from a faulty pump, clogged filter, kink in a fuel line, or a drop in voltage to the pump.... but all of those will show the dropping fuel pressure under load symptom.

If you have stable pressure under load and it still gets lean up top, then you have an injector problem... It's really that simple. But none of these tests can be performed on the stand, you have to have accurate measurement under load. If fuel pressure and AFR's are acceptable and there is no misfire present (but it's still down on power), then you have a dynamic compression issue... which could be anything from the throttle not opening all the way (to include the secondaries) to a hurt motor or flat cams.

And to back Gaz up here, I've been down this road with more than a few pumps, and they all have displayed the same set of symptoms you are describing.... but I've always used instruments to diagnose it (gauges and logging) rather than just throwing parts at it. An AFR gauge and pressure testing rig will cot less in the long run, and you can move them from bike to bike throughout your fixing career.

/soapbox

EDIT: AFR's are indeed Air-to-fuel-ratios, and they require some sort of aftermarket gauge/measuring device to be monitored on a first gen..... they are typically called "wideband gauges" by the aftermarket. Most people in the business of testing/tuning/diagnosing repairs or engines have one or two laying around. :)
 

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Discussion Starter #9 (Edited)
Hoping to get this revived cause I'm still having issues. Thanks Spazona for the input, I definitely appreciate everyone's inputs. I do understand how the fuel put works and the internal filter. Here's the latest. The miss is slight but it is from idle thru revs, pretty consistent. I've road tested the bike and it is down on power and when throttle hard there is a hesitation. I've checked pressure and flow rate at pump and they are both well within specs. I replaced plugs, originals looked all identical in color but replaced anyways. Tested stick coils and they were good but thinking there could be a torn boot I replaced them.Still same problem. Checked cylider compression. Pulled injectors, tested good but to eliminate the possibility I swapped the injectors, throttle bodies, tps. Still the same. I have a PCIII which I disconnected and still same problem. Also flow rate on fuel pump is about 200ml. Checked it 4 times. Have pulled the harness apart to look for corrosion, none. Have checked for kinked or bad wires, none. I'm not new to motors, I've been working on cars and bikes for over 30 years. Any thoughts ?
 

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Discussion Starter #11
Thanks Thundercoupe. I'll start tearing into that tonight. I didn't know they had bad retainers.
 

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Discussion Starter #13
Already tried the kickstand switch, wasn't the problem. I tore into the valve and all within spec except one exhaust valve was tight but still had .0055 clearance. Been talking with a service manager at local dealer, sport bikes are his specialty. He said the valve isn't the issue. Even though I changed still coils he's thinking it's gonna be in a coil arching or wire issue. So I'm gonna run the bike with the tank off and in the dark and look for an arch.
 

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Spray water mist on coils while running. If it bogs you know there's a coil issue. Id check timing marks also
 

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Discussion Starter #16
I was thinking PC also and I completely unplugged it with no change. The plugs seems to look the same but haven't put any real miles on them. I'm going to try the water mist and also run it in the dark to see if I can see an arch.
 

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Discussion Starter #17
I'm pulling my hair out on this. To recap I have a miss from idle thru most of the rpm range. I've been going by the service manual. I've replaced plugs, stick coils, and complete throttle body set up with NO change. Checked fuel pump has proper pressure and flow rate. I checked valve clearance. All were within specs except one exhaust valve that was a little tight. It still had .005 clearance. I did not adjust that valve. I ran bike in dark and looked for spark or arching, have pulled ever connection and looked for corrosion. I pulled on the harness trying to find a broke wire. I have notice the 3 yellow wires coming from the stator are damn hot. They get hot within 1 minute of running. I checked voltage coming form stator and it's 56-57 across the board at 4k rpms. The ohm are .03 or .003 depending on what setting I'm using. So I believe the coils are not shorted or open, is that correct ? With a volt meter on the battery the voltage is 13.9-14.1 from idle thru a rev up. Disconnecting the headlight does not make much of a difference. Does that sound like the regulator is working correctly ? The battery has 12.7 volts and maintains it overnight. I checked 3 stator wires and connectors and they seem fine. Also, would the regulator not working right cause a miss in the coils or injectors ? I know the voltage for coils can be touchy. Any help is really appreciated. I've been talking with a local service manager ( he's a sportbike guy by nature) and he's kinda clueless. But I just found the stator wire issue. The bike is in excellent condition, hasn't seem much rain, always cleaned, never wrecked.
 

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3 things needed for combustion, spark, air and fuel.

I'd dance around the coils to see if you can get rid of the miss. Better yet, even, pick up a set on fleabay and swap them in, dance them through to see if the miss goes away.

One of the plugs should look fouled if there is a miss, or if there is too much fuel (bad Fuel regulator) but you could also have a clogged or dirty injector not putting in the right amount of fuel.

I'd stick to making sure you're getting the fuel and spark you need for combustion as that will likely get you to the root cause faster.

I had an F4i that developed a miss over time and i was replacing plugs every 100-200 miles. fleabay coils and plugs never fixed it. Ended up replacing the FPR and all was right again in the world.
 

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Random thought, have you checked the "joint connectors" taped up in the main harness on the left side of the bike? They can corrode and cause all kinds of electrical problems. I would also say that its time to do a compression test and then a leakdown (positive pressure) test on each cylinder. This will tell you a lot about the overall health of the motor, and it will confirm that mechanically everything is ok. If its all good, then keep chasing the electrical gremlins. Another simple test is to use a spray water bottle and mist the exhaust headers a few times as the bike warms up. If one pipe is cooler than the others you will notice.
 

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Discussion Starter #20
I've changed the stick coils, injectors and throttle body. Did a compression test and leak down and posted those results earlier in the post. I haven't checked any joint connection but I'll do that. My guess is as clean as the wiring has been I'm not gonna find much but I'm up for checking anything. I think I'll be ordering an ecu soon.
 
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