Gas mileage

[pahako]

So I have riding my 81 special for about 3 years now. It has pod filters, more open exaust, 17/32 sprockets, and #45 main jet. I was running a #40 main jet for a couple of years before I put in the #45 jets. I only switched them because I had the #45's and was curious to see if there would be a difference. Honestly, I haven't noticed a difference with the way the bike runs with the larger jets. It seemed to run great with the #40's and #45's. Till recently, I have only ridden around town, and an occasional poker run. Last weekend I went on my first trip on the interstate with this bike. (About 450 mile round trip with an average speed of 75mph) I believe that I normally get 45 to 50 miles to the gallon, but on this trip, it was around 35 miles per gallon. There was a strong cross wind on the way back also. So my question is; Does this seem normal for riding at that speed in the wind, or should I be concerned? I was carrying a little extra weight with tent, and sleeping bag, but not that much extra weight. Normally I can get about 125 miles around town before I have to switch to reserve. I got 105 miles and was completely empty on the way home. (3.3 gallon tank)

Thanks

 

[Growl]

Good question... seems to me that you have only really gotten on the main jets much when on the open road, hence low mileage then. My 81 gets better that 50 mpg in most any situation, even with a passenger and luggage. This is true with 17/30 gearing or with 17/34 gearing. The wild card is the wind... that can really affect mileage so I would do some more testing...

 

[Royboy]

My 78'SE with the same 17/32 gearing gets an average of 63 mpg. No, it's not running lean, no I'm not dogging it and yes, I'm riding at normal hiway speeds, (55-70 mph). I know that seems too high but it's been true for two years and approx. 3000 miles. The bike is kept in a really high state of tune but so are my others and none (including the 77'D) approaches that number.

Having said all that, yours is way too low at 35mpg regardless of load and headwinds. The 45 to 50 mpg you're used to should be easily attainable. Check for a dragging brake, free running wheel bearings, timing, valves, cam chain and carb sync. That energy is going somewhere!

roy

 

[retiredgentleman]

Royboy, what is your secret? 63 mpg is impressive! Are you at lower elevations? Do you always plan your trips so you have a tailwind both ways................just kidding

My 78SE gets 52 mpg in town and 55.8 mpg on long highway trips. I use 17/33 gearing, with stock exhaust and stock airbox/filters. I usually drive at 100 km/hr (62 mph). My long trips are in the mountains, 3400 ft asl to 7200 ft asl, so air is a little thinner, and engine power is reduced.

Once you go up to 70 to 75 mph, the fuel consumption is going to quickly increase.

 

[Royboy]

RG, For quite a while the high mpg numbers worried me, just seemed too good. I felt that it had to be running too lean. The plugs look good and the bike runs cool, (crankcase rarely gets above 225 degrees) KN filters in stock airbox, Mikes XS Commando exhaust system, still running points because I can fix em' on the road if need be but will probably go Pamco one of these days. Elevation around 1200', average ride is 50 to 100 miles. I always run 91 octane, non-oxygenated fuel. Just lucky I guess.

roy

 

[79xs]

I have a 1979 special II. It has the stock 16'' rear wheel with 17/32 gearing. Stock carbs, stock jets, stock air box, stock points, stock coil. I usually run 28 psi front and 30 psi rear. My spark plugs are nice and tan. The bike is in good shape, with only 5,200 original miles.

I get 60-62 mpg pretty much every time I fill up (I always use 91+ octane). I live near sea level, in a fairly flat area. I also only weigh 150 lbs.

Whenever I go on rides out to the mountains, I drop to about 55 mpg. But, them I'm riding in/over the mountains and am a bit more 'spirited' on the throttle.

 

[weaselbeak]

55 mpg should be easily done on a 650. I've been over 60 mpg when riding passively at lower speeds. My trike pulling a Toyota Corolla rear end gets 45 mpg.

 

[retiredgentleman]

RG, For quite a while the high mpg numbers worried me, just seemed too good. I felt that it had to be running too lean. The plugs look good and the bike runs cool, (crankcase rarely gets above 225 degrees) KN filters in stock airbox, Mikes XS Commando exhaust system, still running points because I can fix em' on the road if need be but will probably go Pamco one of these days. Elevation around 1200', average ride is 50 to 100 miles. I always run 91 octane, non-oxygenated fuel. Just lucky I guess.

roy

I'm thinking its the higher elevation here in Calgary (3400' asl) that sets my maximum mpg at 55. Also driving up mountains just requires more fuel. Perhaps if I was closer to sea level, and flat land, I might achieve 60+ mpg

 

[sbtm]

On my 79 I am running unifilter pods (ebay), emgo reverse cone shortys, stock jetting (lean I know, something i might start to fiddle with today). I weigh 300 lbs, rode with my tent, sleeping pad and bag, camp stove, clothes and a 12 pack of beer from Denver, over Berthoud Pass (11,300'). Camped in Hot Sulphur Springs SWA, rode back over Trail Ridge Road (12,180') and back to Denver.

237 miles and 3.54 gallons of 91 octane, almost 67 MPG. I did the speed limit or better on the entire drive. After I re-jet I expect to drop into the 50's

 

[retiredgentleman]

On my 79 I am running unifilter pods (ebay), emgo reverse cone shortys, stock jetting (lean I know, something i might start to fiddle with today). I weigh 300 lbs, rode with my tent, sleeping pad and bag, camp stove, clothes and a 12 pack of beer from Denver, over Berthoud Pass (11,300'). Camped in Hot Sulphur Springs SWA, rode back over Trail Ridge Road (12,180') and back to Denver.

237 miles and 3.54 gallons of 91 octane, almost 67 MPG. I did the speed limit or better on the entire drive. After I re-jet I expect to drop into the 50's

Truly amazing mileage, but a little worrisome with it maybe on the lean side. What do your plugs look like? What sprockets are you using?

 

[pahako]

I may drop back down to a #40 main jet. I am sure the wind had something to do with it, and maybe the speed too. Had to keep up with the Goldwings, BMW, and Streetglide. I check the valves, camchain, and sync the carbs 1-2 a year. The only thing I noticed was the right side plug looked like it was burning richer than the left side.