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Old 03-30-2006, 10:22 AM   #1
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Motorcycle mileage

I ride a Honda XR650L on/off road bike. The best I can manage for mileage is about 50 mpg. I know most motorcycles are tuned for power and not economy, but when cars like the Corolla, weighing ~2500 pounds and with a 1800 cc engine get 41 mpg highway, 50 mpg seems ridiculously low. I just had it tuned at the dealer, too.

With a gross vehicle weight of about 275 pounds and a single 650 cc cylinder, why is my motorcycle mileage so low?
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Old 03-30-2006, 12:44 PM   #2
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i'd say: gearing and

i'd say: power:weight ratio, gearing, and "operator exuberance".

i posted this in the moped thread already, but i rode a baby ninja (250cc, 2-cyl, 8 valve, 14,000 redline, 26 wheel hp, 305 lbs) for a couple of summers a few years ago, and i could achieve 70 mpg (US) hwy at a steady 50-55 mph.

power to weight: this "slow" sport bike (0-60 = 5.5 seconds) developed 1/2 the HP of my firefly, yet it weighed 1/6 as much. relative to the car, it's vastly over-powered (which has FE implications). and remember, the ninja 250 is one of, if not THE, lowest power sport bikes currently available.

gearing: in 6th gear at 55 km/hr (35ish mph) the engine was already turning at roughly 4 - 5,000 rpm (and developing little useful power to speak of - peak hp was 11,000 rpm; torque @ 10,000).

operator exuberance: i think it simply takes more willpower to hypermile a fun, sporty toy than an econobox car, and that's reflected in the numbers.
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Old 03-30-2006, 01:56 PM   #3
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Definitely the gearing

Just looking into the bike's specs the final drive gearing is 15T/45T. Being a dirt/street bike, I'd think that the gearing was set for torque more than anything else particularly since you have a 650cc 4-stroke (also called a "thumper"). If the bike is some what old, it could probably gain something from a carb cleaning. Change the airbox filter, change the oil, etc. maintenance stuff. You might even be able to get a smaller jet(fuel nozzle) for the carb. Just some suggestions.
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Old 03-30-2006, 09:24 PM   #4
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I spent a few summers


I spent a few summers ridding a 1967 honda cl160 twin, it was in rough shape, but never let me down, and alwas got around 72-75mpg combined town, and back roads/longer rides.
Motorcycles are mostly tuned for speed, acceloration, and high power out of a small engine (my brother's Katana 600 has nearly the same HP as my 1,500cc car engine) motorcycles are also not very arodinamic, that is why they might be able to out accelorate a car, but will never have as high of a top speed.
so if you want better mileage out of a motorcycle, getting some good road tires insted of knobbies will be a good start, you can get some on off road tires that are ok for off road, but designed I think it was for 70% road, 30% off road, but pure road tires are going to give you lower rolling resistance, and better wet pavement traction.
It's a big fad to remove your air box, and replace it with a K&N filter, Don't do this, the air box is designed to work with the carburators, and the intake manifolds, it is part of the tuning of the engine and affects how it runs, also, in my personal expearnce owning 8 motorcycles, and at times working at a motorcycle shop, K&N filters let alot of harmful dirt in your engine.
other things you can do:
Use synthetic oil that is designed for the wet clutch of a motorcycle, I use amsoil in all of mine and have noticeds 1-2mph increase in top speeds on my 100cc Honda.
Clean your mufflers, most mufflers have removeable baffles, remove and wirebrush the build up off.
you could go for a smaller rear sprocket, giving you higher gearing/less touqe, for lower engine speed, or you could shift sooner.
if your motorcycle has alot of miles on it, or has been used off road very much, or with low quality air filters, doing a top end rebuild, replacing the rings, doing a valve job, and replacing needed gaskets can restore lost power, and alow you to make better use of the energy that is there, depending on the motorcycle, and the parts needed, you can sometimes do a top end overhaul for $100-150 and 1-2 weekends, of course it helps if you have a book for the bike, and some knolage of what you are doing.
to go to even more extreams, and exspence, a slightly smaller carburator, something like one from a 500, if your's is a 650, will give you a lower peek power, but give you better low speed power and ecconomy.
going for a smaller main jet will lean out the fuel/air mix, and can lead to burnt/bent valves, you can normaly adjust your main needle down a notch if you want it to run leaner, but read your spark plugs! if it's running to lean switch it back befor you do damage.
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Old 03-31-2006, 05:14 AM   #5
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Motorcycle mods

I already have done some work on the bike to improve mileage. I replaced the knobbies with Avon 80/20 street/dirt tires. A also removed the stupid, fake "radiator shrouds" to help the aerodynamics. Damn the stylists! The bike is air cooled, not water cooled!

I also switched to synthetic oil. (Mobil 1)

The last time I took it to the dealer, it was very hard to start, and I asked him to tune it up. When it came back, it was easier to start. I wonder if he re-jetted the carb to make it richer, and if it's reversible.

New taller sprockets really aren't an option. when I try to keep the RPMs down, the thumper engine lugs and jerks really awful. It sounds like the chain is going to throw a link.

Maybe I should just give up and buy a Ninja 250. I hardly ever take the bike off road any more.
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Old 03-31-2006, 09:04 AM   #6
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Sludgy, you sound just like

Sludgy, you sound just like me! I ran my '82 XL500 to 16,000 miles and toward the end it was 95% street miles. Sold it and got a '84 GPZ550 got the same 60mpg, and much much better riding on the street. If you hardly ride on the dirt anymore make the change to the street bike, you won't be sorry.
Keep in mind the Ninja 250 motors are good for only about 60k miles. RPMs kill engines and the 250's don't have much torque for gearing up and slowing the engine down. Look at a Ninja 500 or the cool new 650 with the clean burning engine and gearing them for mileage. You may pay a slight penalty in mileage for the larger motor but I'll bet you'll ride it more and keep it longer than the 250. Riders are getting 50-60 mpg with the new 650 in stock form. Dropping a few teeth in the rear will likely get you 55-65 easy, not far from 250 numbers.
My '88 1000cc Concours gets 45-50 and is well broken in at 184k miles. I've been trying for years to get better mileage out if it but short of just going slow haven't had much success. 3800rpm @ 65mph is just ridiculous for good mileage on a 108hp cycle, blame it on the shaft drive.
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Old 03-31-2006, 10:27 PM   #7
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a good foam air cleaner,

a good foam air cleaner, with the proper oil, and full synthetic oil should help extend engine life a bit, but it's true that those small engines tend to take alot of abbuse from just normal riding, but the Ninja 250 is alot of fun.
you should be able to find out from the mecanic what he did to "tune it up" what I tend to do in a tune up is taking the carb appart and cleaning it, setting the timing, and replacing the spark plug(s) he should not have rejetted it, if it was hard to start it was most likely a dirty carburator, and he cleaned the jets, to make sure the jets stay clean you can add some fuel system cleaner to the gas, but most of the time replacing jets is time consuming enough that a mecanic doesn't just do it, unless he got a carburator rebuild kit that came with new jets, and normaly those are stock sizes, and should stay stock sizes unless you have an aftermarket exuast, and in that case you upjet, or risk not having the bike run right, and risk it burning a hole in the pistion or burning a valve.
to check if it's running rich, or lean, take out a spark plug, and look at it, it should be medum grey, with a little black, thick flat black soot is running rich, really light grey, or white can be to lean, oily soot, just oil meens you are burning oil and that your engine needs a rebuild.
if your engine is lugging, you might try running it at higher revs just for a tank or two of gas, as some engines, when you lug them tend to run richer as they strugle to keep going.
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Old 04-02-2006, 06:41 PM   #8
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bike motors

Most of the power gets generated because the cam timing opens up the exhost valves pretty early - even at idle there is bunning gasses coming out the exhost which you would see if you had the pipes off. Unfortuately this makes a lot of power and low FE - I have a V twin 350 that can get up to about 85mpg if I take it real easy but the italians know how to make a great motor using silicon aluminum bores that are really hard and slippery. You can lean out the fuel mixture a little but the aerodymanics are pretty poor on a bike unless there is a lot of well designed body panels on it. Sometimes a little better carburation will help longer intakes to allow fuel to evaporate might help. Be careful with acetone - the floats in the bowl may dissolve some were made with urethane foam.
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Old 04-09-2006, 10:12 AM   #9
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Carb adjustments

I just got done spiffing up the cycle. It needed to have the mud washed off after a few off-road rides. While I was at it, I did some fiddling.

I noticed that it was idling at high speed since coming back from the dealer, and wondered whether the carb might need adjustment. So, I found the O/M manual, and adjusted the mixture screw first. I closed it about 1/3 of a turn, leaning out the mixture, but the4 bike seemed to idle even faster after that. So, I turned the idle screw to bring the speed down to a more comfy level.

I'm begining to wonder whether the dealer responded to my complaints that the bike was hard to start by richening the mixture. This would account for the poor mileage I've ben getting. I hope the leaner mix and lower idle speed will help.

I'll let everyone know what my next tankful gets for mileage.
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Old 04-17-2006, 06:10 AM   #10
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Mileage report for my XR650L

My last tank was 101.5 miles and 1.94 gallons, or 52.3 mpg after leaning out the carb and reducing the idle speed. This is about 5 mpg better than usual.

It still seems low to me for a single cylinder bike, so I'm going to try leaning it out the carb some more, and using 10W40 oil instead of 20W50.

Ant other ideas?
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