Join Date: Sep 2004
Location: Medford, County of Jackson, Oregon, USA
Model: None at present
If the subfilter has disintegrated due to age particles of it's foam can get into the vacuum lines and other places where it can cause problems. BTW you can make a new foam filter easily out of a piece of the green air filter foam hardware stores sell for lawn mowers. Just cut a piece that fits the holder.
My 1500 averages 40mpg solo and pretty much the same 2 up. Probably because when two up I'm a bit lighter on the throttle. I run Champion spark plugs in the bike so I don't think different plugs will make much difference in fuel burn, most likely it's some crud in the carburetion system or an air restriction due to a poor air filter.
Runa strong dose of Sea Foam through a couple tanks of gas to see if that helps. Check the color of the spark plugs before and after, that will help you identify any gains there. A peek at the vacuum lines would also be well worth while, there's a lot of them and a cracked or loose one could be the culprit.
None at present
Past 'Wings: GL1100, GL1200, GL1500, GL1800
Current BMW C650GT