Awful Gas Consumption.

Bought my 1992 ST1100 with a full tank of gas. Done a miserly 145 KM's on the bike (all city) and the tank is nearly empty. I estimate another 50-70 clicks at best. Is this normal for such a big tank?
Been reading about how a faulty thermostat can contribute to bad gas consumption. Could this be playing a part ?
cheers

doesn't sound right, but try another tankful of fresh fuel of known quality to establish another data point. If your t-stat is stuck open and the bike is running really cold that could explain part of it, but you'd notice the temp gauge staying at the leftmost line (or maybe below) if that were the case. Even a normal t-stat will only bring the temp needle a bit past the left line under steady cruising, so if your temp gauge is in that range your stat is probably OK.

Another thing to consider is the ST fuel gauge doesn't drop to the right "F" line until almost 2 gallons into the tank (about 1.75). So if you bought the bike without actually filling the tank yourself, and just looked at the gauge, you may have started out with a tank that contained much less fuel than you thought. That might explain the fuel consumption figures you quote. The fuel quantity between the "F" line and "E" line is about 4.25 gallons, so if you get 200km out of that portion of the gauge, that wouldn't seem too unreasonable for all stop/go city riding.

If there was stabilized gas in the tank that can explain it as well. I experienced that last year with my ST13. I live in the Chicago area and usually don't ride Dec. 1st to April 30th. I stabilize the gas using the star tron enzyme fuel stabilizer. When I took the bike out after almost 5 months of winter in May of last year, I was only getting about 30-34 mpg in city driving. Usually this number is about 45 mpg. After this gas was used up I filled the tank again and right away the mileage returned closer to normal and after the 2nd fill up it was back to its normal numbers. Hope this helps.

dwalby said:

The fuel quantity between the "F" line and "E" line is about 4.25 gallons, so if you get 200km out of that portion of the gauge, that wouldn't seem too unreasonable for all stop/go city riding.

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That doesn't sound right to me. The tank holds 7.4 US gallons. I'm pretty sure there isn't 3.15 US gallons left when the needle hits empty. Considering the fill up quantities I have done, once the fuel light comes on, I estimate I have about 50 miles in reserve, or about a gallon of gas.

Also, a full tank, with mixed riding, generally gets me around 450 km.

Bush said:

That doesn't sound right to me. The tank holds 7.4 US gallons. I'm pretty sure there isn't 3.15 US gallons left when the needle hits empty. Considering the fill up quantities I have done, once the fuel light comes on, I estimate I have about 50 miles in reserve, or about a gallon of gas.

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You didn't read it right, the gauge stays pegged and doesn't drop to the "F" line until about 1.75 gallons have been used, then 4.25 more from there is about 6.0 gallons consumed at the "E" line.

dwalby said:

You didn't read it right, the gauge stays pegged and doesn't drop to the "F" line until about 1.75 gallons have been used, then 4.25 more from there is about 6.0 gallons consumed at the "E" line.

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+1. That's pretty much what I see. Also, my light comes on when it's hits the E redline. At that point I have 1.4 gallons left.

When is the tank full? When I'm on the road, I fill mine to the top. I put the tank cap on and ride away. When the gas gage needle is straight up, I've used 4 gallons (US). I do some quick math to determine my mpg and calculate my miles left on this tank full. My light doesn't come on. I calculate my mpg every tank. Now that I've added an aux. tank, I'll have to come up with a new system.

I had worse fuel consumption than I thought should be the case, and asked my mechanic to balance the carbs. When I picked up the bike, he told me that I owed him for a tin of floor paint! The problem had been that the chokes were sticking partially on; actually, quite a lot. He freed them all up, started the bike, opened the throttles and a whole load of **** shot out all over this workshop floor. He told me that I needed to take it for a bit of a blast to get rid of all the **** that had built up over goodness knows how long. It improved my consumption by at least 15% overnight, and then I realised that there had always been a whiff of petrol when I got off the bike. Of course, I couldn't smell it when I was underway. That job was back in Dec 2014, and it was an extra because I was concerned, ie not part of the normal annual servicing schedule. When he serviced the bike as per the schedule in July 2015, he noted that the choke mechanism was again partially stuck, although nothing like as badly as previously. I get in there every now and then and give it all a good squirt, and await his judgement in a couple of months as to whether or not they are still partially stuck. That may be an answer, although I realise that it may well be very wide of the mark.

canoodle said:

Bought my 1992 ST1100 with a full tank of gas. Done a miserly 145 KM's on the bike (all city) and the tank is nearly empty.

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A number of possible contributing factors come to mind... i.e.
- stale fuel
- stuck choke
- how much you "wring" the engine? (folks coming from sports-bikes are used to rev between 6 and 8000rpm, which is plain wrong on a SC26 plant :wink: )

A faulty thermostat would manifest by temp gauge reading barely raising while in motion.
Unsync carbs would mainly cause vibrations and reluctant performance

If I only do city driving, lots of stop and go and idling my fuel consumption is in the 30mpg range or 300km per tank. When doing mostly highway speeds I will get 54mpg or 500km per tank. This is a heavy bike, with rider included and gear it's a half a ton of motorcycle (1000lbs), In stop and go traffic that impacts mileage big time.
Your consumption is a touch high, though as others have mentioned, stale fuel etc. always impacts the first run of the season. Consider adding a fuel additive carb cleaner for a couple of tanks. Fill the tank in the morning when fuel is cooler and you get more volume run it on the Hwy for 100kms at 100km/h then fill up and see how many litres you have burned.

kiltman said:

If I only do city driving, lots of stop and go and idling my fuel consumption is in the 30mpg range or 300km per tank. When doing mostly highway speeds I will get 54mpg or 500km per tank.

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Doesn't sound right to me Robert. Is that with either bike? My range is low 40's stop and go/city to high 40's on the road, with both bikes.

I would check for a sticky choke, dragging brakes, and/or a clogged air filter. It's also possible one or more of your carb floats are flakey. Pull the plugs and see if one or more are black.

DeanR said:

Doesn't sound right to me Robert. Is that with either bike? My range is low 40's stop and go/city to high 40's on the road, with both bikes.

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Both bikes the same. Barely a 180 miles per tank with just driving in the city. both bikes on the highway 300 miles per tank

Thanks as always guys for the input. The choke theory interests me. Would a stuck choke mean it's not working ? when I put the choke on "full" there is no increase in revs at all. Seems choke is not operational- does this mean stuck ?

canoodle said:

Seems choke is not operational- does this mean stuck ?

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Could be as simple as an unhooked cable...
Remove seat, side covers and false tank to investigate (choke cable/lever located on LHS of carbs)

kiltman said:

Both bikes the same. Barely a 180 miles per tank with just driving in the city. both bikes on the highway 300 miles per tank

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Me too