Average 35 MPG ? (How to increase fuel MPG)

When my '81 engine was in and making all kinds of noise, I was averaging 34 -38 MPG. After a few carb adjustments and new intake pipe seals PLUS a swap to an '83 engine with different gearing, I am still averaging 35 MPG? I keep reading where you guys are getting 42+ miles per gallon average and want to know what I might be missing here. I am easy on the throttle and only run up to 4K on the highway.

When I picked up the '81 engine from a parts bike, the PO said the carbs were rebuilt and rejetted. I had them rebuilt last year by Pistol Pete with the Randakk kit, but the jets were not touched other than cleaning. The PO was trying to make a street racer out of the bike without success.

Is it possible that the rejetting he did might be the wrong jets and they are causing excessive gas usage? The other question is, are these '81 carbs really compatible with the '83 engine? With all of the other improvements I am finding on this engine from the '81, I can only assume that the carbs were improved too?

Could be 1983 carbs are more gas frugal but I can smell the exhaust at a stop on my '83 and I get between 38-42.

I know that at least the low speed (?) jet is different, 83 is screwed in and I believe 81 is pressed in so there were changes made, maybe jet size also?
I have a 83 rack on the shelf, if you want I can look at the jet sizes.

Where would I find the jet size on the installed jets? If you check the '83 jets, can you tell from a parts fiche if the '81 is different? Also, there is a good chance that mine are aftermarket jets, but I do not know how to confirm that.

gerry when idid all the gearing chanages on my bike everybody thought that i was going to get a lot better gas milage with all that rpm drop..... it didnt happen the mileage stayed the same...it takes a certain amount of energy to go 70mph and if your in efficent zone of the motor 500 to 700 rpm diference in that zone is not going to make any differense..... my bike got 46 mpg before and after gearing chanage....

it got my got so bad at one time i think i was getting about 30mpg thats when i had had enough and started to figure out why and do something about it....i had and still do have a 1990 mercury cougar supercharged xr7 3.8 v6 that would bark the tires shifting from second to third just by stepping on gas and letting it go in drive ,its an automtic....with its air to air intercooler the faster you went the meaner it gets....this car is so efficent that it would get 30mpg and more on trips....so i was getting as good gas mileage with the car as my bike...my bike was totaly on the other end of the scale....idid a lot of things to my bike to up the mpg....

ill make a bet with you gerry start mixing 8oz of atf in your gas per tank for two weeks and check the milage then....dont be shy about running it though the rpm range i dont mean you have to gun it all the time just run it one gear down for the condition and go though the rpm zone from 4 to 7 thousand rpm and gun it every now and then
and ride it normal at times ...im sure after awhile you will be very pleased and the mileage will be better and it will run better....

mine went from the low thirtys to 46mpg and i think im going to get to 50mpg before im done tinkering with this issue...not all the mileage change i got was from atf but the biggest percentage did though....

im very pleased about the mileage and the way my bike is running :yahoo: :yahoo: :music: :mrgreen:

Joe, ATF in the gas? Thats like dropping marvel mystery oil in there isn't it. I might give that I try, but I am still looking for other reasons why it is only averaging 35 when many GL1100's average 42. BTW, the brakes are not dragging and the bike rolls real well, good tire pressure and tread.

mcgovern61":2o9f4v2z said:

Where would I find the jet size on the installed jets? If you check the '83 jets, can you tell from a parts fiche if the '81 is different? Also, there is a good chance that mine are aftermarket jets, but I do not know how to confirm that.

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I'll check the jets tomorrow.

Joe's concept with the fuels of today is right I believe. If ATF troubles you use 2 cycle motor oil. Boat motor 2 cycle oil is good as it cleans and has corrosion preventative additive as well.

The addition of an "oil " of some kind increase's the specific gravity of the fuel. Making it easier for the carbs and jets and all that manage it rather than blowing it out the tail pipe.

After reading a post by Joe I talked to an old bike mechanic friend of mine about this topic and this is his theory but whatever chemistry is going on it does work. My bike seems to have better throttle response as well

tomahawk im glad its working for you...atf is made to keep its passages clean it seals and orings in good shape as it travals ....and thats all it dose till it gets to the spark and gose boom with the gas ther is no down side at all ....im not sure but MMO could have to much cleaner in it to use continuously im not sure ive never used it that way but i am sure about atf and 2cycle oil i wouldnt use seafoam either it has to much cleaner in it to use continuously .....

gerry just do it atf or 2cycle oil 8oz per tank it dont have to be perfect mix as far as ratio theres no down side....

About a year ago somebody over on the Saunders site posted a link about using 2 cycle oil in the gas. They suggested 1 oz per 5 gallons. I was using it regularly for a while and then just forgot to pick back up on it after this winter (thanks for the reminder). It could have just been my imagination, but I thought it ran a bit quieter. I will give the ATF a try now.

joedrum":2ay9py37 said:

i wouldnt use seafoam either it has to much cleaner in it to use continuously ....

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Whats wrong with seafoam?
I think i might try the ATF trick since my bike only gets about 27mpg :fiddle:
My carbs are a little outta sync and the po cut 4 HUGE slits in each muffler so i dont have enought back pressure

I'm going to try the atf.
How many capfulls would egual 8 oz.?

dan filipi":2v0vx5mz said:

I'm going to try the atf.
How many capfulls would egual 8 oz.?

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Probably like 32 or more lol, Its 2/3 of a soda can
You want to get somethin to measure it with, Or get a 16oz coke bottle, Drink the coke then fill the bottle half way with atf :smilie_happy:

At least i think they make a 16oz bottle :mrgreen:

ATF has a high detergent content. This is prolly the reason it is working so well for so many folks. It does clean a little as it goes thru the lines/pump/carbs, but it also helps keep the nasty deposits down on the valves, heads, and pistons. Just remember, if ya get too much in, it's gonna start smoking a little while yer running down the road, but that will burn off. :mrgreen:

My '81 is still gettin 40+ mpg average, as long as I don't hammer on it too many times to pass some slowpoke....not that I would do that, mind you... :nea:

:mrgreen:

Very interesting.

I just got back from a 124 mile ride. It took 3 gallons, 41 MPG.

The type of riding was majority canyon roads I've run many times where I get mid to high 30's.
Needless to say I treated it again with atf at fillup.

So Joe.....what else have you done to improve mileage?

Well now I know what to try first! Of course I am still trying to determine if my jets are wrong.

well some of the stuff idid is not going to apply to 1100s but some will i think .....seems to me that that cold motors dont deisil or perignition wings are cold natured and seem to spit and sputter low rpm and run rich or mine did....i think they suffer from just not burning good or late and lazy ....

it took me awhile to figure out those dyna ignition exactly the way they tell you to set them up one side sets up right and the other side set up late it took me awhile for that to dawn on me .....not a perfect product but when you can git dialed in right its great.....

one thing that you guys cando is open up your air box this will increase oxogen to the mix .....make a new cover that just covers the filter ....this made a big change on my bike

igot the hotter of the two plugs listed for my bike ...it ran better down low in the rpm....i have my own way of modifing plugs and increased the gap for better spark plume i think its called....plan on trying to find hotter plugs that will work i saw soom good in this direction

i also advanced the timing some this seem to improve thottle response....

im still trying and wanting to do more....

i think for 1100s i would modify the air box ,put in the hotter plugs and maybe gap them a little bigger not as much as i did you guys cant play with the timing like i can and keep using atf......the longer you use it the better it will get and it will handle those slight mods ive mention for the 1100s a little time will tell if ive put you on the right path the proof is in the outcome..... :mrgreen:

On a side note, maybe it's my imagination but the irritating knock I've been trying to get rid of seemed be much less noticeable on todays ride. It also seemed to have a smoother bottom end letting me run at a lower rpm with less lugging "clatter".

Fun stuff itis!

dan filipi":3mgbjxq9 said:

On a side note, maybe it's my imagination but the irritating knock I've been trying to get rid of seemed be much less noticeable on todays ride. It also seemed to have a smoother bottom end letting me run at a lower rpm with less lugging "clatter".

Fun stuff itis!

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Maybe I should tried this before I pulled that '81 diesel of mine! :smilie_happy:
The '81 parts bike came with a K&N filter, but I did not use it because it did not sit all of the way down into the gasket. The bike originally had sand in the oil and we never could figure out how it got in there, so I wasn't taking any chances and installed a standard air filter.

This week, I pulled out the K&N and oiled it up, modified it (with a bigger hammer!) and got it to seal at the intake. Went for a spin and boy you can feel the difference in boost! Of course, you can also hear the engine growl through the shelter now too! (Might be able to live with that.) With this an ATF, lets see what happens. :salute:

HMMM dan's mileage went up... Joe's happy with his.... and I am getting in the 40's mostly right at 40 with carbs that may be slightly out of sync.. and running TEXAS 87 +10% ethenol... hmmmm would mine shoot to 50?? who knows.. have to think about this a bit.. 2 cycle mix doesn't run well in my lawnmowers though...

I plan to give this a test today. I am heading to Louisville for a night out with the guys. The trip up there is about 120 miles of Interstate plus some in town driving on both ends.