VFR800 V-Tec, 2006 running issues, too rich?

[smithyvfr]

Hello everyone who reads, I'm Dex from the West Midlands, I got my vfr800 back in April of 2023, and coming up to a year of owning it, its come a long way from the non runner it once was, I was hoping to try and describe my issues.

 

For awhile now the bike has been rideable, I had everything set to stock except for full headers and BW exhausts. The clutch pull off and steady rpm cruising was where things fell apart, acceleration and power is all there, during clutch pull off or slow speed below 4-5k, the bike will grumble and pop, like it's backfiring even during acceleration, I've cured some of its woes by unplugging and blocking the pair valve, it runs incredibly smoothly much like my mates 09 vfr of the same colour, but that all changes when the bike gets hotter, around 75-80° it'll start popping again and almost stutter at slower speeds or cruising. The bike does always have a constant smell of fuel, I'm used to other bikes where they stunk but ran perfectly fine, it is most likely running rich and isn't helping by the full headers.

 

I'll post some photos of her, despite the woes I still love it. For general information, it has recently new iridium spark plugs, the none running state came from some terrible brisk ones, the starter valves have been checked and synchronised, k&n filter and full headers to exhaust, which I didn't put on the bike, many thanks to anyone who reads my rambling but it's always irked me how it's ran and hope for any insight 

[Terry]

Rich running might be caused by the engine coolant temperature sensor or the fuel pressure regulator. 

 

The ECT has two circuits, one feeds the dash readout and the other feeds to the ECM. If the ECM thinks the engine is cold, it richens the mixture. There are some resistance/temperature checks that can be done to determine the health of the sensor.

 

The FPR has a vacuum connection to the intake tract; when the intake vacuum increases it reduces the fuel pressure (so the fuel pressure relative to the manifold pressure stays constant). If the FPR diaphragm has a pinhole, or the vacuum hose connection does not hold vacuum, the fuel pressure will be higher than intended and the engine will run richer. If the diaphragm has a pinhole, raw fuel can be pulled into the vacuum hose as well. 

 

K&N filters have been the cause of poor running elsewhere (VTR1000F) and it might be worth trying with an original or pattern filter. However I would have thought a combination of a freer flowing inake and exhaust would be more likely to produce a lean mixture.

 

Does your bike still have the O2 sensors in the headers; if not (and if no Power Commander or similar is present) this might result in the ECM trying to adjust the mixture and lead to poor running.

 

 

 

[smithyvfr]

7 hours ago, Terry said:

Rich running might be caused by the engine coolant temperature sensor or the fuel pressure regulator. 

 

The ECT has two circuits, one feeds the dash readout and the other feeds to the ECM. If the ECM thinks the engine is cold, it richens the mixture. There are some resistance/temperature checks that can be done to determine the health of the sensor.

 

The FPR has a vacuum connection to the intake tract; when the intake vacuum increases it reduces the fuel pressure (so the fuel pressure relative to the manifold pressure stays constant). If the FPR diaphragm has a pinhole, or the vacuum hose connection does not hold vacuum, the fuel pressure will be higher than intended and the engine will run richer. If the diaphragm has a pinhole, raw fuel can be pulled into the vacuum hose as well. 

 

K&N filters have been the cause of poor running elsewhere (VTR1000F) and it might be worth trying with an original or pattern filter. However I would have thought a combination of a freer flowing inake and exhaust would be more likely to produce a lean mixture.

 

Does your bike still have the O2 sensors in the headers; if not (and if no Power Commander or similar is present) this might result in the ECM trying to adjust the mixture and lead to poor running.

 

 

 

 

I will look into the ECT and FPR, which I already had swapped to another unit with no noticeable results, unless the two I have are both boned, where would I buy a proper one? 

 

I may go back to a standard air filter but my bike does have 02 sensors, I've got block offs for them to hand but always noticed the bike just run exponentially richer when they were blocked off. I have no power commander but I assume that should realistically be my next step with the mods that have been done to the bike.

 

I should also mention my bike has no FI lights present, my main concerns are FPR, ECT or Injectors themselves?