Gen 1 k3 busa, problems in 3rd and 4th cylinders.

[Jape79]

Need help to figure out whats wrong, done almost anything I can imagine and problem is still going on...

3rd cylinder is so rich that spark plug brokes approx. every 1500km. Also 4th cylinder is leaner than 1st and 2nd cylinders. Picture from plugs attached. Bike is running and pulling smoothly until spark plug gets broken. Doesnt loss coolant or engine oil, I have owned bike for little over 3000km.

Done so far:
Synchronised throttle bodies,
Cleaned fuel rail and lines,
Changed injectors,
Checked for vacuum leakages
Mixed ignition coils between cylinders.

Next step would be to measure compression pressures. Any thoughts or other hints?

[busa2001]

Is the bike stock? what mods? power commander etc...

[Thomas]

Check compression, if everything is within limits start looking at wire harness and the ECU. Do you have an oscilloscope?

[Jape79]

It´s almost stock, only mods are slip ons and blocked pair. Bought yesterday meter to measure compressions but it didn´t fit to M10 threads. New try today, if everything inside the limits I´ ll measure the harness. If harness is ok, then I need to find other ECU.

Thanks for the tips, lest see how it goes.

[Jape79]

Okay, pressures between cylinders are inside one bar. I measured also Injector harness according to workshop manual instructions and results were ok. Starts to look that maybe ucu is faulty. I cant quess any othet possible faults anymore why one cylinder is lean, other very rich and rest ok. Has there been faulty ecus on gen 1 busas?

[Oz Booster]

How many miles/Kilometers,
are you sure its rich and not using a little oil on that cylinder

[Jape79]

Little over 64000 km. It consumes slightly  oil, about 0,5l in 3000km. I think that this little oil amount shouldn’t kill plugs os even make it dark colored, right?

[Thomas]

Starts to look that maybe ucu is faulty. I cant quess any othet possible faults anymore why one cylinder is lean, other very rich and rest ok.

Could be intermittent short to ground of one the injector wires.

Has there been faulty ecus on gen 1 busas?

Haven't heard about that.

[Thomas]

Also try swapping injector connectors for 3 & 4 or 2  & 3 cylinders. I imagine the idle will be rougher as FI phasing will be well off in low RPM range but in mid / high RPM you should be OK.

[RansomT]

Starts to look that maybe ucu is faulty. I cant quess any othet possible faults anymore why one cylinder is lean, other very rich and rest ok.

Could be intermittent short to ground of one the injector wires.

Has there been faulty ecus on gen 1 busas?

Haven't heard about that.

Within the wiring harness...there is a connection that ties the grounds together that a LOT of times is cause of misfires.  That connection is located near the "flat section" of the harness under the tank above the rear swing arm pivot.  It's the only flat section of the harness.  If you split the harness there you can see the connections.