Poor Fuel efficiency

[Dogma]

Replace the air filter so you can check that off the list. I've proven to myself that if you let one get gunked up enough the mix gets too rich and fuel economy suffers.

Also, high cruising speed can knock mileage down. I usually get in the low 40's on my 1000G, but slab sessions at 80 mph can be below 35. I don't know if you've already accounted for that or not.

[gustovh]

Look at your plugs, what do they tell you? Are they dark, dark brown or black or nice and tan like they should be. That is where I would start with the Sherlock Holmes routine.

V

[mrbill5491]

My carb vent/breather hoses end under my seat in a dead air space via the stock routing and are well above and behind the carbs.

[1980GS1000E]

With regards to the vent tubes above the bowls. Mine was siphoning gas out at speed and I was getting fuel starvation and horrible mileage. I then ran the vent tubes up to the tail end of the fuel tank. That solved the problem. It may not be stock routing, but it sure works.

[Steve]

The tubes are supposed to terminate in a STILL AIR pocket, not in the rushing air stream.

Air blowing over the tubes will siphon fuel, regardless of termination height.

.

[1980GS1000E]

It must have been turbulent where they ended, then. I can't remember where that was. Might have been along a frame rail.