Unacceptable gas mileage

[flyingace]

I have 35K on my 850L and get between 35-40 city. My compression is on the low side (120s-110s), so it can't be said that low compression alone can cause bad mileage. My engine idles and runs cleanly throughout the rev range - just lucky - it always has.

A high idle could mean a vacuum leak or bad head gasket or out-of-synch carbs. If you have low compression, it can be lots of things. You need both a compression and vacuum gauge to really diagnose a problem.

[tfb]

Shortlid,

There's no way I would be happy with 30mpg -- it's not much better than a car! It's likely running too rich, which is not a harmless state of affairs.

For one thing, it will lead to accelerated wear of the pistons, rings & cylinder sleeves, because the excess fuel actually interferes with the lubrication of the fine oil film that's left behind with each piston stroke.

Also, your engine oil will deteriorate more rapidly with more unburnt fuel residues blowing past the rings into the crankcases, so there will be accelerated wear across the board.

You should be able to get over 40mpg at least, but mpg in the high 40s (eg. 47mpg) can be reasonably expected with GS and GSX Suzukis, with a tuned engine in good condition.

Sometimes it's best to take the guesswork out of things, and get the bike dyno'd to check the air:fuel mixture right through the rev-range. That will tell you where it's chewing the juice.

Mike.