Mileage and jetting By twowheeler (Read 918 times)

[rks]

Apr 13, 2014 20:02:42 GMT -6 twowheeler said:

So 50mpg on a 50cc would be a problem

If it were my scooter it would be.

The 150cc scoot in my profile picture has covered 3045.3 miles since it's first fill-up (Apr 18,2012), til it's last (Apr 13, 2014). In that time span, I have put 40.401 gallons of gas in the tank. That works out to 75.37 mpg average for every mile since new. Also should say that I replaced the original 105 main jet with a 115, when miles on odometer were 366 to compensate for air box removal, and K&N cone filter install.

After all, isn't fuel economy about the only advantage a 50cc has over a larger displacement scooter?

[Alleyoop]

bada bing bada boom
Alleyoop

[Alleyoop]

Apr 14, 2014 14:55:41 GMT -6 JR said:

Don't forget it all depends what the temps are where you live, if it is on the cold side the motors require more fuel and therefore use more fuel. If the temps are hot then the motors require less fuel and your mileage goes up. But I do have to agree for a stock 50cc a 85 main jet I really think you could go down to an 80 at least. Gonna disagree with that. The cold air is much more condensed than hot air. When that enters the cylinders it gives a higher compression which gives the motor more power causing it to work less. Less work = better MPG.When it is colder out, more air can be crammed into the intake manifold in which the air/fuel mixture will burn stronger and more rapid instead of sluggish. That's one good thing about cold air intakes, it not only gives you more hp, but it also gives you better mpg. Cold air can carry more oxygen per unit volume than warm air.  Heck some of the old dragster folks used to take cans and put ice around the fuel line to get the effect of cold fuel and more HP. Even water has more oxygen if it's colder. Let's not also forget gas is blended different in the winter which effects MPG. We all know that a scooter with these small especially air cooled engines run faster in colder temps due to the engine running cooler which lets the engine run at less RPM. Less RPM = more MPG.I remember two summers ago when it was over 100F+ here for 31 straight days and riding my 250 to Perryville one day in 106F temps and thinking she sure is sluggish today and it's water cooled. Today it's 55F and I promise you she'll have a lot more ump and get better MPG along with it. Temp/MPG has a curve of what's the best just like the HP/RPM curve and on the average depending on those old other factors called humidity and sea level engines will do better all the way around in temps from 60F to 85F tops, go above or below those again depending on other things to a degree and the engine especially air cooled will not perform at it's peak including MPG.

All that you said is true, BUT what you just did is make the motor run LEAN to make more hp BUT that also will make things RED HOT and with the way the young and wild ones run them the motor will go KABOOM. Take your cars in the winter you use a lot more gas WHY because you get that nice cool air in and if you don't add more fuel you will have motor problems. The dragsters they run lean as heck but ONLY for a short run even some of the short runs some go KABOOM.

What I said is in cold temps motors need more fuel DUE to the cold air which will lean out the mixture if leaned out to much you will be walking that puppy home.
Alleyoop

[JR]

Apr 14, 2014 15:07:59 GMT -6 Alleyoop said:

Nice post now fix it so we can read it
Alleyoop

Man I don't have a clue as to what happened? Maybe V5 had a brain fart?   It was so garbled I couldn't read it?  All I'm saying is engines running hotter work harder = less MPG.

I also agree with lowering the jet, if it'll run at max speed/rpm with a lower jet it's very possible in colder temps he's just running fuel out the tail pipe. Best MPG temps are in a range of 60F to 85F also depending on sea level and humidity.

JR

It had a weird "requote%" right in the middle, it was a brain fart. But I fixed it for my pals. Mr. Sleep head JR just went to bed instead of fixing it! You're welcome! Rich

[JR]

That goes to what I said, he changed his jet and is throwing more fuel to it so he needs more air and if the air makes it lean it runs hotter but doesn't use more fuel? It will only use the fuel that the jet allows to go to the engine based on the throttle. If he runs it wide open in 50F weather it will get better MPG than running it wide open in 95F weather. A hot engine slows down, works harder and does not optimize the fuel to it's best HP/RPM curve = less MPG.

When it comes to engine temp the middle is the best MPG area, not too cold or too hot. What gets me is folks who jet too big, even though they can make it run well with adjustments and actually gain nothing.

How many times have you seen a lower jetted carb adjusted correctly run the same speed as a higher jetted carb adjusted correctly also? We both know the intake only allows so much fuel, more than that is just wasted time.

JR

[cyborg]

All i know is that guy trying to get on top of that table is hurt real bad,,,that hurts just seeing it JR

[cyborg]

OK now that i'm over the shivers of that guy being in a chair the rest of his life,,,i try to always jet a little fat as i like aircooled engines and it gets damned hot here,,,never had a problem,,,,i'm sure i could get closer to stoichiometric,,but run the risk of a lean condition and burn something up,,,so i'll loose a little mpg and power probably

[JR]

Apr 14, 2014 17:06:27 GMT -6 cyborg said:

All i know is that guy trying to get on top of that table is hurt real bad,,,that hurts just seeing it JR

Yea? How bout this poor dude?

[jvino]

Yeah my scooter gets a little bit better than 60 miles to the gallon. But for a 50 and 50 miles to the gallon something doesn't seem right.

[jvino]

Thanks for that video jr that make me chuckle.

[jvino]

I agree I also would rather run rich than to lean and overheat a motor and like alley says kaboom.

[cyborg]

where are you finding this stuff JR???

[richardv]

Wow! My 1200 Gold Wing got 48mpg at 65mph and the stereo blasting.

[Alleyoop]

The Stereo blasting is what was pushing it, sort of like a jet car
Alleyoop

[richardv]

Polkas where the best.

I miss that old gal.