Look, a mpg thread

[Pain]

Yeah, I know there are a lot, that is the problem. I can't find what I want in all the chaf.

I hve a 81 standard, with a79 special motor in it that has had the 750 final drive conversion and gets all over 30mpg. Since my 80 special without the final drive conversion gets better.

There is also a stumble under 3k rpm, just ot have full disclosure. I know the carbs weren't jetted right, since I had plug fouling problems last year. The carbs were re-jetted over last winter (To my personal shame I don't know what they are now, my mechanic did it, but he researched here, so I'm guessing it is stock for 79), but I haven't ridden it until the past week or so (Wire harness problem).

What I'm looking for is someone who is getting good mpg (Something over 40 would be good) to let me know what their set-up is, or any other hint at what might be wrong.

Thanks

[bikerphil]

carb set-up

Hey Pain, I have a 79 Special and I get 40+ MPG with the following set-up. BS34II carbs (early type 78-79) with stock pilot jets (42.5), 2 sizes up on the mains (142.5), modified airbox (drilled and snorkel cut off 1" from base) with K+N filter and 4-1 Mac exhaust with modified baffle (straight tube with slip on cheapo baffle). She runs a tad on the lean side but pulls hard and smooth thru all RPM ranges. I also run the 750 FD and a small Slipstreamer windshield. When I bought this bike, the PO had the carbs all dicked up with way too large jets. It fouled out plugs and stumbled at about 3-3.5K. Oh, also floats set to stock setting of 25.7 mm.

[randy]

Pain,

My entire setup is listed below in my signature. I get a consistant 44 MPG. I've done other things like lapped the valves, replaced valve seals and keep the valves adjusted, check 'em every winter.

[oseaghdha]

I am pulling a consistant 40, unless I run 80-85, then it's more like 30.
Straight stock (137.5/42.5) except for a 4into1 of unknown parentage.

I should have an 850 FD waiting for me when I gethome from Shanghai.

FWIW, it seemed to make no difference when I installed my Vetter, still right about 40MPG either way.

[randy]

Other things that might be wrong:

Low tire pressure
dragging brakes
heavy right hand
valves out of adjustment
carbs out of synch
vacuum leak
fuel leak

[TADracer]

Check for a weak spark too.

My setup is similar to bikerphil (exept I run pod filters) and the last time I did a really good milage check I think it was 41.6 MPG or perhaps it was 41.2. Either way it was over 41 MPG.

I used to get low-mid thirties and I had my Dynacoils ballasted when they should not have been. On some advice I took care of the ballast problem and my mileage shot up to over 41 and all was right with the world.

If in good tune I see no reason that something around 40 MPG should not be attained, even if carrying bags and a fairing.

[81xsproject]

Don't be afraid of your carbs. Get in there and see what you've got. No body else has asked, so I will. You said you have an 80's bike with a 70's motor. What are the carbs from, 70's or 80's? While your in there, take a look at your jet needles and needle jets (slide needles and emulsion tubes). If the needle shows heavy wear and/or the hole in the top of the emulsoin tube that that needle slides in and out of looks worn out of round, that can be a huge mpg killer as it allows more fuel to be pulled from around 3.5k-6k rpm. This is the problem I have with my carbs and I only get around 32mpg. However, I am too cheap to replace them with FI project nearing completion.

As a side note (with a grain of salt) I emailed the guy that makes Cambell's X-Pipe exhaust recently and he told me that after putting the X-Pipe on his GS1100 Suki, he gets 70 mpg. Sounds a little too good to be true to me, but it did peak my interest a little more.

[Wildkat]

I get around 40 pretty regularly...

unless I'm running twisties... or with certain members here who like to go just a little on the fast side (and even then, I get around 37)

I'm running a 78 engine with 79 carbs (137.5 mains and 42.5 pilots), stock airbox (with Uni-filter)and the 750 Final drive mod... Mac 4 -2 exhaust...

[Pain]

Don't be afraid of your carbs. Get in there and see what you've got. No body else has asked, so I will. You said you have an 80's bike with a 70's motor.

Oh, I'm not worried about taking the carbs apart. On my special I've had them off a lot this summer fiddling with the jetting and floats. Its more a matter of wanting to know what I should have before I go and look, so I know what might be wrong.

[Dan Hodges]

Passing Gas & Volumetric Efficiency

I was out today (November 2nd.) on a 200 mile run which consisted of about 150 miles of Interstate and 50 miles of river road running on route 3 along the Missisippi river to Grafton Illinois and back home to St. Louis. I got 40 mpg going up and 44 mpg coming back which is the best I have ever got with this bike. Going up I had a couple of impromto races with a couple of big Jap V-Twins on Interstate 255 but never got above 7500 rpm. Coming back home I was running about 75 to 80 mpg on the Interstate and got 44 mpg. Presently my combo consist of a 1179 Wiseco kit, Super/Trapp 4 into 1 header with a 2.5 inch core muffler, Mega-Cycle cams, ported head, drilled air box with K&N filter, 40 degrees of ignition timing @ 5,000 rpm, Dyno-Jet kit installed per instructions with the exception of different diameter vacume holes in the diaphragms and #130 main jets. Mention is made, a # 130 DJ jet is not the same size as a #130 Mikuni jet. I also have the 17" rear wheel with a Bridgeston Battlax 45 series rear tire on my 81 Special which adds about 3-5 mph at 5,000 rpm which helps my mileage I'm sure. I have a small National-Cycle (Streetshield) on an otherwise naked Special. My Special in similiar trim bone stock would fetch about 34-36 mpg when it was new and I had one combination that would barely get 30 mpg. Presently it's doing better than it ever has in all catagories but I've been working on it for two years straight and I think I've finally got it right. These old Eleven's were never known for their sterling gas mileage in stock form but with the right stuff they can do much better than new.

[Ivan]

I am pulling a consistant 40, unless I run 80-85, then it's more like 30.
Straight stock (137.5/42.5) except for a 4into1 of unknown parentage.

I should have an 850 FD waiting for me when I gethome from Shanghai.

FWIW, it seemed to make no difference when I installed my Vetter, still right about 40MPG either way.

I get similar results to this. 60 mph will pull about 40-45, and 80 going back and forth to work gets about 32-34

[dbeardslee]

I kept screwing around with my carbs, mixture, etc. and kept getting right around 32mpg with my normal city driving. Went for a long leasurely ride last weekend without all my normal throttle twisting and was over 40mpg. Riding style makes a HUGE difference in your fuel mileage. Stop and go city riding is also a mileage killer.

[LCS249]

... Going up I had a couple of impromptu races with a couple of big Jap V-Twins on Interstate 255 but never got above 7500 rpm. ...

Hey Dan,

How did you do against the V-Twins?

best,

LCS

[Dan Hodges]

River City Rumbling

Hey Dan,

How did you do against the V-Twins?

best,

LCS

One of them was an absolute pooch and one was a Yamaha with some kind of funky chrome strips on the side of the gas tank with loud pipes and belt drive. Actually the thing ran pretty good untill about 90 mph then it was all over. We started from about 65 mph and I was in high gear and he actually jumped out on me for a little bit but by about 80 I was pulling by after which the party was over. We were on I-255 and I ran up to 125 or so and slowed back down to about 80 but didn't see either again. Some of the big Jap V-Twins are starting to run pretty good and I will only mess them on the Interstate where I've got some running room. A lot of these idiots want to race in town and I won't do it because there is not enough room to really get it on. I love beating up on V-Twins on the Interstate and my Super Special is very strong on the top end. What's really a joke are those loud popping Harley's, they are absolute dogs.