Reduced Fuel Economy

[rummy63]

On my '06 K1200S at about 29500 km, the fuel economy slowly reduced from 4.8L/100 km to 5.2L/100 km. I was on my way to BMW Motorrad for the 30,000 km service so I figured after the valve adjustments and service, the declining fuel economy would be corrected. However, on my 350 km ride home, the fuel economy continued to worsen. When I parked my bike at home, the fuel economy had reduced to 5.6L/100 km. I am baffled why, within a 1000 km, my fuel economy would go from 4.8L/100 km to 5.6L/100 km. Any ideas what could cause this drastic change in fuel economy? The bike sounds and performs as good as ever and I am not riding the bike more aggressively than normal. The weather has been between 33 and 38 Celsius where I have been riding. The air filter was not changed during the 30,000 km service and the valves did not need adjusting; they were within acceptable ranges. There were a ton of bugs on the bike. Could it be that the air filter is clogged? Any ideas would be appreciated. Thank-you.

 

[cjack]

I had something like that happen for one tank full on a trip out west. The next tank full went back to normal.

 

[pauls1150]

Possibly more than 10% alcohol in the gas?

 

[cjack]

It was "no ethanol" pump. Maybe it had water in it.

 

[dashbaugh]

If the mileage doesn't improve as mentioned by others; you may have a bad O2 sensor in the exhaust pipe. The ECU depends on it for AFR when it goes closed loop. So if your air readings are haywire the fuelling will also be way out.

 

[KillerBee]

If the mileage doesn't improve as mentioned by others; you may have a bad O2 sensor in the exhaust pipe. The ECU depends on it for AFR when it goes closed loop. So if your air readings are haywire the fuelling will also be way out.

If an O2 sensor was out wouldn't it cause the computer to generate a fault code and trigger a check engine light? Would a no spark situation do the same?