First of all thank you all for the previous advice i have had on this website. Secondly i want to apologise if the following question/query is daft, stupid etc. The reason i am asking is i have next to no experience of motorbikes in general (got my full license Aug 2018), so i have a steep learning curve. My fuel consumption has taken a tumble yet when the fuel warning light comes on i can only get about 13-14 litres of petrol in it, yet the tank should hold 20 litres. I have replaced the spark plugs (that was fun), to no improvement, next on the list is the air filter. I watched a youtube video on removing the fuel pump unit under the seat, to see if there was any obvious problems and i was wondering if there is a physical separation between the main fuel tank and the auxiliary, that could be causing me problems. I have a 2011 650gs and when i got it 2 years ago i was getting 60+mpg now riding it the same way its dropped to mid 40mpg at best, over the last few months and the range is 140-150 miles on one tank.
Firstly is the fuel capacity not 16 litres on your bike? It doesn't have an auxiliary tank, unless it has a fuel tap (hence the reason for a fuel gauge and a low fuel warning light) the 4 litres you mention is the amount of fuel that is left (out of the 16 litres) when the low fuel light comes on . Problem is unlikely to be in the fuel system so I would leave pulling the fuel pump out until you have exhausted all of the other common checks for this type of problem. Change your air filter before you do anything else. What colour were the plugs that you removed from your bike?
Last edited by ZebraDriver; 20-06-2020 at 04:46 PM.