running very rich

My g650 was running very rich for a while, it had new plugs and a clean filter, so i disconnected both the airbox and co2 sensors, that made a bit of difference, so i reconnected the airbox sensor,just leaving the co2 one disconnected. It does seem a bit down on power now.
Its still using more fuel than it used to, does anyone have any ideas ?,
Does the co2 sensor cause problems on these bikes ?

The valves were checked at 30,00mls and were fine, the bike starts and runs well and doesn,t use any oil.

Its now on 50,000mls.

tee bee said:

My g650 was running very rich for a while, it had new plugs and a clean filter, so i disconnected both the airbox and co2 sensors, that made a bit of difference, so i reconnected the airbox sensor,just leaving the co2 one disconnected. It does seem a bit down on power now.
Its still using more fuel than it used to, does anyone have any ideas ?,
Does the co2 sensor cause problems on these bikes ?

The valves were checked at 30,00mls and were fine, the bike starts and runs well and doesn,t use any oil.

Its now on 50,000mls.

Click to expand...

I assume you are disconnecting the O2 sensor on the header pipe? the O2 or lambda sensors in fuel injection vehicle send a message to inform the ECU when the bike is running rich or lean. I have not heard of any going before on the GX bikes but yours is higher miles than most and they are considered a consumable part on modern cars. It is likely that this is your problem however other issues can cause problems with FI. On other vehicles, I have known weak batteries and dirty/corroded connectors to affect the signal received by the ECU but I doubt this is your problem as I understand that the GX bikes run slightly lean when the battery is weak.

As much as I like to carry out my own maintenance, this might be a time to consult the professionals. Your local bmw dealer will be able to hook the bike up their diagnostic computer and read any stored fault codes and confirm a diagnosis which may well cost less than replacing parts which are in working order.

Thanks rossi, i think a visit to the dealer is probably the most cost effective option,even though i hate the idea.....

Mine runs perfectly with the lambda removed. 20k on the clock still get 60-70 mpg depending on use and sprocket.

yes it was the lamb sensor,bought one secondhand from germany, seems they meteorite with bad fuel and mileage.
I think bmw use the same one for nearly all their models.