MPG and modifications poll

[CatatonicBug]

Old wives tale. Gas expands, but not liquid in any appreciable amount with one exception (mercury). Leastwise that's the official side of the story. If it did you would have a burst tank or gas spurting out of the vent hole in the hot sun right after fillup!

I have had that very thing happen several times. Fill up on a cool morning, and ride the .2 miles to work. Then, come out at lunch and the sun has warmed the tank enough that there is a huge puddle of gas all over the ground, running down the tank. I have learned that I can only fill up when I know I will be riding a couple miles immediatley afterward or I will make a big mess...

[Axel]

yup - the very same

[fredintoon]

Old wives tale. Gas expands, but not liquid in any appreciable amount with one exception (mercury). - - -

Hi John,
with very rare exceptions (invar etc.) everything expands with heat. The colored alcohol that's in modern thermometers for instance.
Canadian gasoline pumps have a sticker on them saying "volume compensated to 15ºC" to compensate for the fuel's density varying with it's storage temperature.

[cywelchjr]

Old wives tale. Gas expands, but not liquid in any appreciable amount with one exception (mercury). Leastwise that's the official side of the story. If it did you would have a burst tank or gas spurting out of the vent hole in the hot sun right after fillup!

That doesn't match with the experiments we did in high school chemistry. We did several experiments with several liquids to not only prove the expansion, but to measure the expansion rates and the differences between different liquids. Not only that, but H2O also expands as it changes to a solid, which is why you can crack your engine block in a water cooled engine if the coolant freezes.

[jetmechmarty]

Old wives tale. Gas expands, but not liquid in any appreciable amount with one exception (mercury). - - -

If I fuel my hot motorcycle right to the lip, close the lid and walk away, why does the gasoline run out the top?

I fuel a heavy jet as part of my job. Why can I put a lot more fuel in it (by weight) on a winter day in Anchorage than I can in Thailand?

I think old wives have a lot of tales.

[skids]

If I fuel my hot motorcycle right to the lip, close the lid and walk away, why does the gasoline run out the top?

I'll give it a shot. The bottom of the fill neck is below the "airspace" at the top. You fill it with cooler gasoline and the engine rapidly attemps to make more "air" (avoiding the use of the word "gas"). If this increased volume of air has to push on the liquid surface because you filled it slightly above the bottom of the fill neck, it will of course push the liquid upwards.

[skids]

Here is a link that talks about specific weights vs. temperature.
http://www.faqs.org/qa/qa-2617.html

[doramide7]

i got 49.1 mpg running 60-65 mph today open highway high humidity,overcast,s.c hwy 11 scenic route nice country.

I wonder if the PO of my bike jetted the carbs. It's only had 2 tanks of gas to go by; but, I am lucky to get 31mpg. The bike has a K&N filter in stock box and an Accell ignition, coils & wires. I haven't pulled the plugs to check for carbon or proper gap but she does smell a bit rich.

[cywelchjr]

I wonder if the PO of my bike jetted the carbs. It's only had 2 tanks of gas to go by; but, I am lucky to get 31mpg. The bike has a K&N filter in stock box and an Accell ignition, coils & wires. I haven't pulled the plugs to check for carbon or proper gap but she does smell a bit rich.

What kind of riding are you doing getting 31? If it's around town and stop and go that's doing pretty well, most get at or below 30 in around town stop and go driving. If I get out onto the road, where it's not so much stopping all the time I get 36 to 37 MPG.

[trdriver71]

What kind of riding are you doing getting 31? If it's around town and stop and go that's doing pretty well, most get at or below 30 in around town stop and go driving. If I get out onto the road, where it's not so much stopping all the time I get 36 to 37 MPG.

I am lucky to be getting 25mpg on the highway at 65mph right now but admittedly I have to get my carbs synced.

[cywelchjr]

I am lucky to be getting 25mpg on the highway at 65mph right now but admittedly I have to get my carbs synced.

Even with my carb sync being pretty bad I still got around 37 on the road. I've never gotten as low as 25 even around town, that's even with hammering it from light to light and full dress. AAMOF, before I had the trunk and hard bags I got over 30 around town most of the time and almost 39 on the road.

[trdriver71]

Even with my carb sync being pretty bad I still got around 37 on the road. I've never gotten as low as 25 even around town, that's even with hammering it from light to light and full dress. AAMOF, before I had the trunk and hard bags I got over 30 around town most of the time and almost 39 on the road.

Yeah can pass almost anything but a gas station On the highway have to fill up once every hour when the light comes on.

[justme1100]

I am riding 2 up most of the time and I am very hard on the throttle as well.

[fredintoon]

Old wives tale. Gas expands, but not liquid in any appreciable amount with one exception (mercury). - - -

Hi John,
re-reading this string I (finally) realized why you'd say that.
It's a combination of advancing age and risky lifestyle that's mixing up your memory of those high-school physics lessons.
You are confusing thermal expansion, which occurs in almost all solids, liquids and gases, with compressibility which happens with gases alone.
Which is why your engine and your brakes work as they do.

[ddragon63]

its all about riding style... My other ride is an R1 so i don't ride the xs too hard, if I'm in the mood for fast I'll take the R1. but on open freeway and hwy with the XS I'm a 60+ mph rider... Fully dressed riding 2 up I average about 33-37 depending on where we're going