ST1100 bad mileage, common problems?

tom_eaton

tom_eaton

Joined
Jan 10, 2008
Messages
25
Age
37
Location
Portsmouth, UK
Right guys, where do I start?

The ST has had around 30 (that's right, 30!) mpg for at least 4 or 5 tankfuls now (since i started checking after each fillup), and rather than go plowing in I thought I would check with the hive mind also known as ST-Owners.com. What have been the key causes in a drop in efficiency for you?
 
How does the engine sound, perform?

You could check to see if the brakes are dragging.

Maybe add some Techron or SeaFoam to the tank to clean out the carbs.

How's the oil? Is the choke stuck open? Are the carbs synched?

Just a few of the things I can think of off hand.

Bill
 
A bad vacuum fuel valve has been reported to allow raw gas to bypass the carbs and get sucked into cylinder 3. What. Does the #3 spark plug look like? Is it darker than the others?
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Given the number of possible causes, I'd jump in. At the very least it's gonna require pulling the carbs.

Check for vacuum leaks, dirty idle jets, torn slider diaphragms, stuck choke plates, <obvious> leaks.

Good luck and keep us poSTed.
 
i just got finished tearing around the country, and i got 46mpg. now don't flame me, but if you're talking uk gallons ( .83267 of a u.s.gallon) that should translate to about 38 mp u.k.gallon. so that does put you a bit lower but not all that much. i'
d start with the easyest first. check the plugs, if they'r wet, i'd try bypassing the fuelvalve and see if that dosen't inprove mileage
 
You've got it backwards the_gr8t_waldo.

46 mi/usgal = 55 mi/ukgal.

The imperial or UK gallon is larger than the US gallon, by about 20%.

My ST1100 usually gets 52-55 mi/impgal.
 
My ST1100 can get over 50 mpg, if I take it easy with the fun lever.

As others suggested, easy stuff first:
Brakes dragging?
Air filter clogged?
Spark plug colors?
Tires properly inflated?
"Choke", fuel enricher really off?

Then:
Wheel bearings?
Vacuum leaks.

Have fun
 
I know you folks in the UK have problems with rust. Pull the fuel tank and check it for leaks. I have heard of a few that have rusted through. Also make sure that the enrichener valves are returning fully to the off position. Might be sticking or have a problem with the cable. And don't forget the obvious dirty air filter.
 
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