82 mpg on a 250? - can that be right? By grocerygetter (Read 1,210 times)

[grocerygetter]

took my first long ride of the season though didn't pick a good morning to start out.
45 degs cloudy damp and windy.
Haven't had a chill that deep in me for many yrs. but stubborn as I am I kept going cuz the sun was supposed to come out by noon.
It did come out and warm up thankfully.

I toured thru the flood devastion from last spring. Most roads have been rebuilt.
Pictures do not do it justice. Pretty amazing to see entire hillsides gone and now rebuilt with stone rubble from the granite quarries.

Back to my story.
I did 230 miles Saturday thru farm country.
50-55mph most of it.
Rolling hills.
At 140 miles I filled up since I can't trust my gauge below 1/4.
I filled it to where I always do.
The vent line in the filler neck. I filled it to that when I left Home.
It took 1.67 gals.
Do the math.
140/1.67 = 83.83mpg.
Can that be right?
Has anyone don that on a 250 Jonway yy t?
I haven't filled up since the trip back home but I expect that to be worse since I struggled up thru the Notch in Stowe.
I'll post that tank back later this week when I fill up.

I do need to do the clutch rollers/weights and get the grease out. Seeping rviht now as it get hot.
And I do need to change the jets.
She struggles up hills. Won't "gear down". If you stop and start again up the hill she takes off fine but as soon S you get some speed and the clutch starts to adjust for the higher speed, she starts to slow down until you pull over again and start all over.

It will be interesting to do the same trip after the updates. Wonder if the mpg will be slightly worse wih better performance.
She absolutely does 70 mph right now no problem and like to hold speed around 65.
But those nasty tires gotta go as well.

[JR]

45F!!! Say what!!! It's got a good chance of hitting 100F here this week, no rain in sight and I'm stretching out the water hoses this morning for summertime watering! Only good thing about hot, dry, weather the grass doesn't grow!

Yes and from what it sounds like on the way out a lot of downhill cruising, you did only 50 to 55 MPH and at 45F the engine ran very cool and sweetly, yes 82 is possible.

Now since you mentioned all you did let me give you some good "hillbilly" advice on the 250 sine I ride in the hills!

Get 12g sliders, clean the variator up and put her back together nice and clean. This will give you the ump up the hills and not kill the top end.

Pull the diaphragm and rasie the needle one notch, if it's already raised as far as it will go add one tiny thin brass washer, it will help believe me.

Tires? Myself I use the Avons and I go bigger, 140/60/13 on the rear, 120/70/13 on the front. The bigger on the front helps correct the speedo by about 3 MPH. You'll love the look of the bigger wider tire on the rear and they wear better and are smooooooooth.

JR

[bullet]

Yeah, why not? My Royal Enfield, 500cc single and my wife's 250 Honda Rebel average 75 MPG. I just did a check on my 08 Jonway 150. 88.3 MPG. Its flat here, most of my riding is at 30-35 MPH with some 40 mph cruising. I am very easy on the gas and I only weigh 165 lbs. And yes, the odo is in miles. My Royal Enfield at a 45-50 MPH cruise at 2,700- 2,900 RPM will easily top 80 MPG. And yes, your MPG will drop the faster go by a lot.

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[mauiboy]

Sure, it's very possible! The cold temps will help, they make air and fuel denser, so a gallon of fuel will hold slightly more actual fuel (a mild version of why an icecube will take up more space as water after it melts than it did as as ice), the air holds more oxygen, also a long run will get you better fuel economy. The way the engine is tuned will help, if you are cruising in the sweet spot for that engine you will get great mileage.
The Royal Enfield is a great example. I love RE's btw
The RE 500 next to my burgman 400 engine. The RE is 25% higher displacement. Both are singles. Here is where it gets fun, the bore vs stroke. The width of the piston and the distance it moves up and down. The RE is an undersquare engine, the burger is an oversquare engine. The RE will produce more torque (all else being equal) and the burger more hp. The RE outputs ~27bhp and the burger ~33bhp (from a smaller engine). The RE develops 40nm torque, the burger about 37. The real killer is the fuel economy, the burger gets about 60, the RE in the 80's (although the burger is about 80lbs heavier).
What it all comes down to is that the RE was designed to be a less stressed engine, sat in its happy place, cruising at say 50mph it will return far better mpg than the burger, its engine will last longer (all else being equal) but the burger will probably equal or slightly outperform it even when giving away 100cc in displacement. Both engines were well designed for their intended purpose. Your 250 is also a very unstressed engine, it could probably get even better mpg if it were fuel injected. 82mpg under good conditions is very doable
en.wikipedia.org/wiki/Hypermiling

[cruiser]

I believe your mileage as being very doable. Cold, damp air is best for making power on a gas engine.

I have never really checked my mileage. Cleaning the variator and changing weights will give you the best performance boost. YY250T's usually have 23 to 24 gram roller weights from the factory. Most people get best results using Dr. Pulley 19 gram sliders. No lubrication necessary. This is if you have the 244cc Honda clone engine with 6 weights. This setup will increase acceleration and allow better hill climbing ability while maintaining the same top speed as stock weights.

[grocerygetter]

Great feedback. Thanks.
I was slightly curious because I keep hearing people talking in the 60mpg range.
A guy at work with a Reflex clocked himself at 68mpg once. But he does ride it hard.

I knew about the temp vs power. We used to hang out at a closed shopping mall parking lot Friday and Saturday nights and comment on the good horsepower weather nights.
I clearly remember a 350 Chevy Vega with a 6/71 blower hooked up in the industrial park on a cold damp dewy night and almost flipped it over backwards scraping the back bumper, and he had been quite the contender before but it was clearly a different animal that night.

I've always felt that small variations in parameters seem to easily affect these smaller engines. So though my day was nasty to start, I got a whole day of riding in for around $10.
I can really feel the difference in performance based on temperature.
Makes me think the whole cooling system is so poorly designed, basically no thought in it, it's just there.
Everytime my fan comes on and it's below 60F I think about the people down south on a summers day and how taxed these cooling systems are.
That last ride made me think about modifying to keep the engine in that lower temp range.

I'll update this post with more long rides for comparison.
And after the 50 other things on the top of my list I'll get to that variator and jets.