Cure for spluttering ZZR1400

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Q. I’ve owned a 2008 Kawasaki ZZR1400 ABS model from new. Recently when it’s at about 60mph in fourth or fifth gear it will start to splutter as if it is running out of petrol or firing on three cylinders.

If I pull over and turn the bike off with the key and start it again it could run fine all day. It’s never been power washed and the petrol tank breather is not blocked. If I change down to third gear it will run perfectly, or get above 90mph it clears up.

The bike has a Power Commander 5 fitted and the earths are on the battery, I’ve fitted new plugs too, so I’m starting to think it could it be the ECU breaking down.
Pat O’Connor, email
A. You are right to check and change the plugs, as they should be replaced every 7500 miles. If one of them looked sooty or worn, then that would be the first thing. Did you check the stick coils for similar signs of wear?

As you have a Power Commander fitted you may well have an oxygen sensor eliminator fitted in the loom, too. If so, check for corrosion on the connections.

The reason we're pointing you in that direction is because when the engine is running slowly in the top three gears the fuel injection is in closed loop mode and taking readings from the oxygen sensor, primarily to clean it up for emissions.

If that sensor has gone west, or isstarting to break down it will make the bike run really rich. It doesn't use the sensor in third gear so the problem goes away.

Having said all that I'dexpect an EFI warning light to come up if the oxygen sensor was at fault, and the fault isn’t usually intermittent. But an eliminator fault wouldn't be picked up by the engine management system as it's an aftermarket part.

The sensor sticks out from the exhaust system just where it goes from four pipes to one. I’d recommend you get a dealer to run a diagnostics check.

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