Best speed/rpm for fuel economy? GS850

[93Bandit]

I filled up today when the fuel gauge read ~1/8th tank. I wanted to run it until I had to switch to the reserve but I was in heavy traffic and didn't want to risk stalling and struggling to get it started again.

Anyways, over 116 miles I got 40mpg. About 50/50 city with traffic and 65mph highway. Not bad.

Anyways, how much fuel is left when you go to reserve in a peanut tank?

[Steve]

Anyways, how much fuel is left when you go to reserve in a peanut tank?

That would depend on at least two factors:
1. Assuming it's the '83 850L in your signature, the overall tank is 4.5 gallons, and ...
2. Depending on the petcock that is installed, there is 1.1 to 1.2 gallons left in REServe.

You can check this at home, but it will require a small assortment of containers. Start with a full tank. Run a fuel line from the petcock to an empty gas can that will hold about 4 gallons. Using another hose, make sure the petcock is in the RUN position, then apply vacuum to the petcock to open it, letting it drain into the 4+ gallon can.

When it stops, note the position of the needle on the fuel gauge. I like to see it at the transition from the white line to the red line at this fuel level. Move the output hose to a smaller container. A 5-quart oil container from your car's last oil change would be near-perfect. Move the petcock lever to PRIme or REServe. They both draw off the same opening at the bottom of the tank, but REServe requires vacuum, PRIme does not.

When the fuel stops flowing, you will know:
1. How much gas is in the main tank.
2. Where the needle is at the transition to REServe.
3. How much fuel there actually is in the REServe tank.

I tend to do these steps whenever I get a new bike, just so I can see whether i need to adjust the fuel gauge.

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[93Bandit]

Thanks Steve. I'll have to do that test next time the weather isn't good for riding and I have some free time.

When I bought the 83 L, the PO told me the fuel gauge wasn't very accurate and when the needle would dip into the red, it was "empty." I'm not sure if he meant empty and need to go to reserve, or he already burned through reserve empty. It didn't start sputtering in me yesterday and it was well into the red while on a smooth level road.

[Steve]

Follow the procedure in post #47, you will then know where your transition is.

One other thing to keep in mind: if the screen on the inside of the petcock is missing, you will have NO reserve.

Besides being your main fuel filter, it also provides two different levels of fuel entry. The upper one is for the 'main' tank, the lower one is for reserve and also for priming the bowls. If the filter is missing, you will always be drawing off the bottom of the tank, so will have no reserve at all. Following the procedure in post 47 will help you determine that.

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[93Bandit]

Oh, good to know! Is it common to lose the filter? Or do you mean if a PO replaced the petcock and the filter didn't stay in tack?

[Steve]

I would not say it's "common", but it is possible that somebody might have removed it for cleaning or working on the petcock, then might not have gotten fully-seated on re-assembly. It's also possible that they left it out entirely or simply damaged it to the point where it does not work properly.

Draining the tank into a can, using the procedure in post #47 will at least tell you that it's there, but it won't tell you if the filter media is intact.

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