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Join Date: Mar 2006
Location: Kyle, Texas
The reserve portion of your gas tank is but a name, nothing more. The petcock has two tubes on it going up into the tank. One is shorter than the other. On your bike, your petcock is always driven by vacuum, whether set to ON or RES. So, sitting and waiting for gas to dribble with the bike turned off is a waste of time with this petcock. It only opens when vacuum is applied. The twin tubes in the petcock sit similar to this (il) where the little letter i is the short tube and the letter l is the long tube. In the ON position, the gas is being drawn from the long tube, and when in RES, from the short tube, giving you the "reserve" fuel. All bikes are different, as all vn750s are different. Depending on your fuel mileage and how full you fill your tank, you might get 120 miles before being forced to switch to reserve, where someone else might need to switch at 110, or 140 miles. Driving habits, weight and how well your bike is running all help determine how far you can go.
I would check your mpg over the next maybe three tanks of gas and that will give you some idea of what is going on. The filter is a screen around the tubes in your petcock, unless someone has installed inline filters on your fuel lines leading from the petcock to the carbs. If you wanted to, you could remove your tank and petcock to check the screen and such, and if you did that I would take that opportunity to flush your tank clean. If the filter and tank are already clean, it won't make any difference.
The fuel gauge is another thing that will read different on every bike. Use it as an estimation, not the gospel. It will start out reading full for the longest time, as your tank is larger at the top, but once the gas gets down into the lower part of the tank, you seem to be able to watch the gauge move while you ride! Not quite, but it feels like it.
Once you know what your average fuel mileage is, then I would ride the bike and intentionally run out of gas in the ON position of the petcock, switch to reserve and then go get her filled back up, then keep the amount of miles you got before running out as your rule of thumb. I'm sure you are resetting your trip meter on the odometer every fill up, right? That number will be a far greater indicator than the fuel gauge. By the way, you should familiarize yourself with where the petcock is located so you can switch to reserve while the bike is still running instead of running the carbs dry before switching over. It can be done pretty smoothly if you practice it on a lonely road a few times. It helps to do this because you still have vacuum applied and the carb bowls will fill more rapidly, keeping you going. When I first got my 1500 I was on a 4 lane road, passing a semi when my bike started studdering. I was able to move it to reserve and continue on without hardly slowing down, although I would have chosen a more remote location to try that the first time!
I typically start leaning toward a gas station at 100 miles on the trip meter, just out of habit.