I have a weird mileage issue in my CB Honda Hornet motorcycle. This is a version specific to India, https://auto.ndtv.com/honda-bikes/cb-hornet-160r
It has a 160cc engine.
During the first 1000 Kms, I got an average of 33 km/l, with normal driving, never above 90 km/h and a decent break-in. I went to the service center they performed a mileage test, and driving at ~40km/h they managed to get 47 km/l.
They said they will do some adjustments, and did some tappet adjustment, reduced the idle and gave the bike back to me. This time, I got around 36 km/l, with very careful driving.
When I took it back, they refused to take it and I had to argue for 3 hours before the general service manager himself took it for a test drive, drove normally with around 50 km/h top speed and got only 40 km/l.
I told him this is how it is and if I cruise at 60 km/h, this goes down even more. He agreed, took the bike, and they replaced jet needle in the carb and gave it back, claiming they got 60 km/l when driving economically.
I drove, and surprise, I got 36 km/l. I figured there might be a very minor leak, and closed the petcock every night. I ended up getting 42-46 km/l (45.6 km/l when cruising at 90 km/h on a highway road trip).
However, if I left the petcock on, the poor mileage returns. The authorized service centre tried to reproduce the issue, but they could not, and got 44 km/l with the fuel cock on over the course of three days. I took it back, filled with 1.3 L petrol on Friday and the bike hit reserve on Monday with 36 km on the trip meter.
Note that there is no way someone is stealing the fuel. The vehicle is in shade both at home and office.
What could be the issue?
- The mechanic told me that people only get 35 km/l in Hornets. Is it true?
- Is it possible that the carb might be slowly leaking fuel so that I see a mileage issue only when I take longer to consume a litre of fuel?
My next step is to get a mileage-testing bottle, fill it with some petrol and let it hang overnight to see any reduction in fuel level. My suspicion is that there is some minor issue with the float. How do I prove it?
The AFR is perfect since the mechanic showed be a good maroon burn in the carb. He is very polite, hence I don't wish to override him, but he says he cannot report this to Honda and get the Carb replaced since he cannot reproduce the issue. What do you think I should do?
Here is a link to the Mileage reported by one of the users on XBHP: Avg 50 kmpl nearly.