Fuel mileage, miles on bike, needle jet size


Information and questions on GL1100 Goldwings (1980-1983)
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David2953
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Joined: Wed May 19, 2010 10:36 pm
Location: Minnesota
Motorcycle: 82 Honda

Fuel mileage, miles on bike, needle jet size

Postby David2953 » Wed Aug 17, 2016 10:32 am



I recently bought a 1982 GL1100 with 25,000 miles on it. I had to rebuild the carburetors and the engine runs great, but the fuel mileage is not normal. It only got 33 mpg on the first tankfull. I think it is caused by the midrange throttle circuit being too rich, presumably because the needle jets are too big. But, could the needle jets already be worn at 25,000 miles? If so, theoretically, mileage would decrease as miles increase on all bikes with jet needles. Is this happening? What mileage do you get and what miles are on your bike?

I rebuild lots of carburetors for lots of different models bikes, but I don't check fuel mileage because it would take too much time. I know Keihin needle jets are almost always between .101" and .104", but I normally do not measure them precisely like I do the pilot and main jets. The needle jets do not have a size written on them to check the diamter to like the other jets usually do, so I just clean them. If a bike requires a change in midrange mixture, I change it by moving the needles up or down.

What size should the needle jets be? I can't find a specification for that. I can't find a source that sells them by size either. They are not even included in kits. How would I get a certain size?



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RBGERSON
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Location: SCOTTSDALE, AZ
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had every year from 75 to 83

Re: Fuel mileage, miles on bike, needle jet size

Postby RBGERSON » Thu Aug 18, 2016 7:56 am

Gas mileage is very rider dependent. Can be as high as 45 or so and as low as 30 depending on speed, throttle cranking, weight, tire pressure, head winds, wind screen height etc. I doubt that the jet is worn could have been replaced with wrong size?? Take her out on the highway, one up and run a tank at 55mph and see what your mpg is..42 or better and your good, less and you've got issues..check your plugs for color they may tell the story.
HAD LOTS OF GOLDWING 75-83
NOW INTO 1500'S..RIDING A 1998 SE

FAIR WINDS,
RB

David2953
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Joined: Wed May 19, 2010 10:36 pm
Location: Minnesota
Motorcycle: 82 Honda

Re: Fuel mileage, miles on bike, needle jet size

Postby David2953 » Thu Aug 18, 2016 10:54 am

Thankyou Rbgerson, there is hope for this forum yet. I was thinking maybe someone changed the needle jets. There are no numbers on them. Does anyone know what the inside diameter should be? I can measure them with great accuracy. I made a tapered pin out of a .104" drill. I put it in a drill press shank-down and polished a taper onto the shank so it goes from .101" to .104" over about 1/2". I can put black marker on it and slip it into the jet and it makes a distinct ring where it touches, then I can measure the pin at that spot with a micrometer with great accuracy.

I dropped my needles .048" and my mileage went from 33 to 42 with the same riding style and similar conditions. The next tankful was 39.8, but I spilled some gas working on my fuel pump that got air-locked, so it would have been a little higher. I'm not sure I want to settle for 40-42. I could make further mods, but I want to know whether the jets are the standard size first. This needle drop modification should not have been necessary and I can easily undo it by moving the shims from above the needles to below the needles. I may do that if I discover the needle jets are oversize. I know .001" change to the jet needle diameter or the needle jet diameter makes a huge difference. Can anyone tell me what diameter is standard?

Also, the needles could be worn or the wrong size. They have 55D on them. Does anyone know what that means? I found kits available, Keyster KH-0387N, for about the price of the OEM jet needle and needle jet combination. The Keyster kit appears to include jet needles and needle jets and the needles are D296 in one ad. What does that mean and are they the same as OEM or have they been made with more clearance in favor of more power and in disfavor of mileage?

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spiralout
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Location: Alabama
Motorcycle: 1975 GL1000 (gone)
1980 GL1100I (with '77 1000 engine)
1996 GL1500 SE

Re: Fuel mileage, miles on bike, needle jet size

Postby spiralout » Thu Aug 18, 2016 2:34 pm

What made you think that the mid-range is rich because of jet wear? Just the mileage for the one tank? Have you chopped the motor and checked the plugs? You could very well be overthinking this.

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maintainer
Posts: 291
Joined: Sun Mar 22, 2015 11:39 am
Location: Houston, Texas
Motorcycle: 1977 GL 1000
1982 GL 1100 Interstate (Sold)

Re: Fuel mileage, miles on bike, needle jet size

Postby maintainer » Thu Aug 18, 2016 3:01 pm

Something is not right,
My 82 GL 1100 would consistently run 160- 180 miles per tank and typically refill with 4 to 4.5 gallons. I don't ride to get good mpg and usually cruise at around 75 mph on the highway. I tend to be kind of throttle happy and wind it out thru the gears pretty often.
Mine always started instantly and ran great except one time when the fuel filter clogged and needed changing it would bog some in upper rpm's.
The times I did check mpg's it was always 40 or above.
1982 GL 1100 Interstate SOLD
1977 GL 1000 Standard (naked can be good, who knew?)

David2953
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Motorcycle: 82 Honda

Re: Fuel mileage, miles on bike, needle jet size

Postby David2953 » Thu Aug 18, 2016 10:45 pm

I don't really believe the needle jets are worn at 25,000 miles, just wanted to know what others thought or what others know about that. Something was making my mileage low and the midrange mixture was the most likely cause. I did not need to try to read my spark plugs to know that. I calculated the mileage by the trip meter and the gas pump. Yes, one tank was plenty enough for me to be sure there was a problem.

I modified my carburetors to get better mileage, but now I am thinking that shouldn't have been necessary and maybe the needle jets were not the originals. I didn't think about that at the time, but it is possible. I am trying to find out what size they should be and what sizes are available, so when I take mine out I can measure and decide what to do. Does anyone know what is the standard needle jet inside diameter?

I typically go 70 if the limit is 65 and 75 if the limit is 70 and I still want to be getting closer to 50 mpg than to 40 mpg.

Yes, Maintainer thankyou. Now more like Maintainer please, more, more.

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spiralout
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Location: Alabama
Motorcycle: 1975 GL1000 (gone)
1980 GL1100I (with '77 1000 engine)
1996 GL1500 SE

Re: Fuel mileage, miles on bike, needle jet size

Postby spiralout » Fri Aug 19, 2016 12:27 am

I don't know man, all I can tell you is to keep machining on your carbs until you get what you're looking for then go to work as an engineer for Honda because, you know, comparing that first tank full of as sort of stock, then machine sh*t, then compare to the next tank full will tell you a lot.....

David2953
Posts: 28
Joined: Wed May 19, 2010 10:36 pm
Location: Minnesota
Motorcycle: 82 Honda

Re: Fuel mileage, miles on bike, needle jet size

Postby David2953 » Fri Aug 19, 2016 8:53 am

The purpose of this thread is not about machining carbs, but jetting them properly. What is the proper size of the needle jet inside diameter? why is that spec so hard to find when the other jets that have less affect on mileage are clearly marked with numbers that tell their diameters. For instance, a #140 main jet is supposed to be 1.40 mm. A #35 pilot jet is supposed to be .35 mm. The needle jets are not marked, but we should be able to measure them to tell if they are stock and there should be some options from there. Lots of people change their pilot jets for richer idle mixture and their main jets for a richer wide-open-throttle mixture, but most of the running time of these engines is on the in-between area, the needle jet.

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spiralout
Posts: 1049
Joined: Sun Feb 17, 2013 6:41 pm
Location: Alabama
Motorcycle: 1975 GL1000 (gone)
1980 GL1100I (with '77 1000 engine)
1996 GL1500 SE

Re: Fuel mileage, miles on bike, needle jet size

Postby spiralout » Fri Aug 19, 2016 9:45 am

David2953 wrote: Lots of people change their pilot jets for richer idle mixture and their main jets for a richer wide-open-throttle mixture, but most of the running time of these engines is on the in-between area, the needle jet.

I disagree with that on these old GL carbs. You'll find there's not many who tweak these carburetors like what you're used to working with and that's probably why you can't find any info on the stock needle jet size. There's no following nor market for modding 'em.
I still think you're overthinking this and have't run enough tanks through to have started modifying the carbs the way you have.
I also think that you chose the wrong bike to try to tweak to get 50mpg at interstate speeds. It's a heavy 35 year old flat four...

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Wingsconsin
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Re: Fuel mileage, miles on bike, needle jet size

Postby Wingsconsin » Fri Aug 19, 2016 4:03 pm

I found that a carb synch could be helpful..
You have to aim for perfection to realize the results -
But after a carb rebuild on our 1980 GL1100 it was delivering poor fuel economy.
Once I got the synch 'perfect' the power went up and so did the MPG - But 44-45 is all it would ever deliver.
It was my sons bike and he weighed in at about 180 lbs. Most of the riding was done on country highways at around 55 MPH +/-
There are so many variables in MPG that carbs are not the single answer..
Tire pressure, brakes dragging, bearings in axles, additional drag items like wind wings or a large windscreen can all play with the performance -- Not to mention riding style ; heavy acceleration , or even hill country vs flat riding... (Kansas, Nebraska)
It took me several hours to get the synch exactly correct - but it was worth it.


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redbug
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Motorcycle: 1983 Gl1100I
1986 Harley FLHT

Re: Fuel mileage, miles on bike, needle jet size

Postby redbug » Fri Aug 19, 2016 5:26 pm

Mike Nixon"s goldwingcarbs.com should fulfill your needs for these carbs plus a lot of reference if you haven't been there before. Stay after it.. this is very interesting..


" Ridin on Tulsa Time "


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