Poor Gas Mileage on my 1990 SE


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garywyoung
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Poor Gas Mileage on my 1990 SE

Post by garywyoung » Sat Mar 03, 2018 1:58 pm



This past January, I purchased a 1990 SE GL1500 with 54K miles on it. The bike runs lovely, idles smoothly, accelerates without complaint. It's a sweet ride. But even though I only ride just me, only accelerate moderately (I'm no speed demon), and carry no luggage, I average 21-23 MPG. In other forum discussions, I've read about folks who get from the low 30's to the upper 40's (although I find this latter one a tad hard to believe), but I've seen no one mention getting such low mileage as I do. With as poor gas mileage as I'm getting, I half expect to leave a trail of fuel on the road as I ride--at least this would explain things. So I'm hoping some of you folks can point me toward a few things I can look at. And to save some of the guesswork, here is some additional information:
  • Current Tire Pressure: 32 psi
  • Spark Plugs are not fouled
  • New timing belts
  • No missing, backfiring, surging, etc.
  • 87 octane Shell fuel
  • Moderate acceleration and liberal use of 4th and 5th gears at speeds above 40 mpg
  • Mixed driving conditions (highway and city)
Thanks for any insights you can offer. Or, if you too are beleaguered by lousy gas mileage, I'd certainly feel better knowing I wasn't alone.



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Dusty Boots
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Re: Poor Gas Mileage on my 1990 SE

Post by Dusty Boots » Sat Mar 03, 2018 2:57 pm

Tire pressure far to low, Front should be at lest 38 - 40 and rear 41
Have you changed the air filter in the last while?
Brakes sticking/dragging? How many miles on current set of plugs?
What type/height of windshield are you using?

I typically get 35 -38 mpg @ 60-65 mph when loaded down for touring.




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dingdong
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Re: Poor Gas Mileage on my 1990 SE

Post by dingdong » Sat Mar 03, 2018 4:23 pm

I agree with Dusty. 32lbs is much too low tire pressure. That would be the first place to start. I use those same tire pressures he suggests. I "normally" get 34 to 38mpg 2up riding on the highways. I have actually gotten as much as 48 mpg on occasion on my 93 at higher elevations in the mountains and twisties of Rockies.
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ct1500
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Re: Poor Gas Mileage on my 1990 SE

Post by ct1500 » Sat Mar 03, 2018 6:19 pm

Just about every 1500 is capable of 36-42MPG or more. What you think is a perfect running engine cannot be with mileage like that and there is something else going on. The engines run so smooth on a properly tuned one that often times the uninitiated can be lulled to think all is OK with their machine that might have a couple of faults if they don't have another one to compare it to. I tried to word that the best I can hopefully it came across.
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AZgl1800
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Re: Poor Gas Mileage on my 1990 SE

Post by AZgl1800 » Sat Mar 03, 2018 6:21 pm

agree, tire pressure should be close to 40....

some Sea Foam in the gas for a few tanks....

how is the idle? any surging at all? that can be a sign of leaking vacuum hoses.
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garywyoung
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Re: Poor Gas Mileage on my 1990 SE

Post by garywyoung » Sun Mar 04, 2018 8:16 pm

Thanks for all of your responses. Granted, I’m new to the GL1500, but I’m not new to motorcycles or engines, so I feel confident that it’s not secretly running poorly and I just don’t realize it. So I’ll change out the air filter and plugs, increase the tire pressure, check the carb sync, and report back when I’ve learned more.

Thanks again!

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Stew
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Re: Poor Gas Mileage on my 1990 SE

Post by Stew » Sun Mar 04, 2018 8:42 pm

While you're changing the air filter visually inspect the choke plate is opening all the way when the choke is off.
Winging it every chance I get 8-)

19,119 miles when I got it from dad Oct 15, 2017 --- 22,072 miles and counting as of June 14, 2018!

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AZgl1800
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Re: Poor Gas Mileage on my 1990 SE

Post by AZgl1800 » Mon Mar 05, 2018 12:53 am

while changing the air filter, there are a couple of air filters down on the right side of the engine, I think one of them is used for the cruise control?

my '94SE when I bought it back around 2006, both of those filters crumbled to the touch, just turned into powder...
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bellboy40
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Re: Poor Gas Mileage on my 1990 SE

Post by bellboy40 » Mon Mar 05, 2018 9:52 am

The two filters John is referring to are the cruise filter and the sub filter. He is correct that those are neglected items for maintenance and usually they will just crumble and turn to powder when you start to replace them, especially the sub filter. The cruise filter is located on the left side of the bike behind the fairing inner cover. The sub filter is located on the right side of the bike behind the right fairing inner cover. Here are some pictures to help with that.

Cruise filter
Cruise filter


Sub filter
Sub filter


garywyoung
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Re: Poor Gas Mileage on my 1990 SE

Post by garywyoung » Sun Mar 11, 2018 9:48 am

Those are two filters that are entirely new to me—I’ll search them out. Would those filters affect gas mileage though?

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bellboy40
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Re: Poor Gas Mileage on my 1990 SE

Post by bellboy40 » Sun Mar 11, 2018 1:05 pm

No those filters probably won't change your gas mileage but they do need to be changed if they have been in there a long time, which they most likely have been. The sub filter, on the right side of the bike, could put some pieces of the crumbling foam filter in the carbs where it could cause some difficulties.
Go ahead and take care of what has already been suggested (air filter, tire pressure, spark plugs) and see how it goes.

Lutzinmn
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Re: Poor Gas Mileage on my 1990 SE

Post by Lutzinmn » Mon Mar 19, 2018 8:37 pm

I am also new to GL1500. I have a 92 GL1500 SE. I also get poor mileage in low 20. Engine seems to run fine. I replaced plugs. Did not seem to help much. I am thinking I need carbs cleaned. I don't know when done last.

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Bluewaterhooker0
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Re: Poor Gas Mileage on my 1990 SE

Post by Bluewaterhooker0 » Tue Mar 20, 2018 12:18 am

Let me ask a question of both the low mileage riders. When you have experienced these low mileage incidents, do you do a lot of cold starting and short trips ? In other words, do you make short trips that require fuel enrichment, or choking a cold engine ? I have noticed that my mileage goes straight down the tubes if I use the fuel enrichment lever to choke a cold engine for starting. The more of that I do, the worse the effect. Most of my riding is trips of 75 - 150 miles, with limited stops, and no enrichment for restarts after I stop. Under those conditions, I usually see 35 - 42 MPG. Top speeds of 70 mph eat gas as well. But, a tank of gas that is used throughout a week, with enriched cold starts, and the ensuing cold idle to warm the engine, 5-7 times, will destroy my MPG. Under those conditions, I'm lucky to get 30 MPG. I believe that is pretty normal operation. The choke, or more accurately, enrichment, and the associated warming period of 4-5 minutes will really suck down your gasoline and kill your mileage. My engine is VERY cold natured.

garywyoung
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Re: Poor Gas Mileage on my 1990 SE

Post by garywyoung » Tue Mar 20, 2018 5:41 am

You make a really good point. I purchased my bike this past November, so since then I've only experienced it in cold weather, with cold weather starts (employing the fuel enrichment lever, yes) and rides of 15-20 miles every week or so just to keep things from gumming up over the winter months, so you could very well be on to something. Once (if?) the warm weather gets here, I'll be able to enjoy longer rides and get a better sense of the kind of gas mileage I'm getting in fair weather.

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Re: Poor Gas Mileage on my 1990 SE

Post by Bluewaterhooker0 » Tue Mar 20, 2018 7:46 am

garywyoung wrote:
Tue Mar 20, 2018 5:41 am
You make a really good point. I purchased my bike this past November, so since then I've only experienced it in cold weather, with cold weather starts (employing the fuel enrichment lever, yes) and rides of 15-20 miles every week or so just to keep things from gumming up over the winter months, so you could very well be on to something. Once (if?) the warm weather gets here, I'll be able to enjoy longer rides and get a better sense of the kind of gas mileage I'm getting in fair weather.
Well, there ya go. And I don't know where you're from, but my "cold" starts are in Florida. Not so cold. On those rare days when I start it in 40F weather, those cold starts are that much worse. A lot more enrichment, for a lot longer, thus much more gas wasted.

Lutzinmn
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Re: Poor Gas Mileage on my 1990 SE

Post by Lutzinmn » Tue Mar 20, 2018 4:28 pm

I am in Duluth MN. I use cold starts and do short trips around town. I also do over 75 mile trips. I seem to get similar mileage either way. I will try to do a more accurate check when I get bike out of storage.

Lutzinmn
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Re: Poor Gas Mileage on my 1990 SE

Post by Lutzinmn » Tue Mar 20, 2018 7:00 pm

I was able to do a compression test today. All cylinders were between 97 and 99 psi. Good news they are all fairly equal. The bad, this seems low to me. Could this be hurting my fuel mileage?

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AZgl1800
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Re: Poor Gas Mileage on my 1990 SE

Post by AZgl1800 » Tue Mar 20, 2018 8:43 pm

Lutzinmn wrote:
Mon Mar 19, 2018 8:37 pm
I am also new to GL1500. I have a 92 GL1500 SE. I also get poor mileage in low 20. Engine seems to run fine. I replaced plugs. Did not seem to help much. I am thinking I need carbs cleaned. I don't know when done last.
before you do anything at all, get a few cans of Sea Foam and treat every fill up with a half can each time.
Continue for at least 3 cans of SF...

In my case, with a 94SE that was in "poor running condition" the day I traded for it, it took about 4 months of daily driving to work/back. 18 miles each way. I used the bike for 'daily transportation' because my "other car" was a '98 Dodge dually diesel rig.... 12-15 mpg in town..
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ekvh
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Re: Poor Gas Mileage on my 1990 SE

Post by ekvh » Tue Mar 20, 2018 9:54 pm

Lutzinmn, did you compression test with throttle wide open? There is a difference of opinion on whether this is needed or not, but the shop manual calls for wot. My bikes are around 100-120 with the throttle closed, but 170ish with the throttle open. You are probably fine.

Lutzinmn
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Re: Poor Gas Mileage on my 1990 SE

Post by Lutzinmn » Wed Mar 21, 2018 10:46 pm

For some reason I can't remember. I will try compression again and make sure I have throttle wide open. I hope that's why it was low. Per my manual it should be between 185 and 242 psi.

Also I will hold off on carb work and use SF for awhile. Thank you all for your feedback. Much appreciated.

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AZgl1800
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Re: Poor Gas Mileage on my 1990 SE

Post by AZgl1800 » Wed Mar 21, 2018 11:17 pm

Lutzinmn wrote:
Wed Mar 21, 2018 10:46 pm
For some reason I can't remember. I will try compression again and make sure I have throttle wide open. I hope that's why it was low. Per my manual it should be between 185 and 242 psi.

Also I will hold off on carb work and use SF for awhile. Thank you all for your feedback. Much appreciated.
Poor compression is nearly always fixed after a few hundred miles of riding.
My brother took a Chevy V8 that the heads and manifolds had been stripped off, it was setting under the rain spout at his shop for several years.... One day, he needed an engine that size, so he took it and soaked it in rust penetrating oil for a couple weeks, then he put a big break-over bar on the crank shaft and started wiggling it.... he gained a tiny bit of movement each day, and finally was able to get it to turn over..... then he installed a starter motor, and jumpered the posts to a battery and let it run for a long while, spraying the cylinders with ATF...

He drove that car for several years after that, it ran just fine.
See you at NASR-11 July 10th, 11th, 12th 2018

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garywyoung
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Re: Poor Gas Mileage on my 1990 SE

Post by garywyoung » Fri May 18, 2018 2:05 pm

Time for a follow-up on my original post: Replacing the air filter made no difference in my gas mileage (which didn't surprise me, as the previous owner had just replaced it before I bought the bike), and as expected, replacing the sub-filters did nothing either (they needed replacing, however; they were dry-rotted). So, anyone want to guess what made the difference? Replacing the rear tire.

I'd noticed a slow speed wobble when I was cornering that I mistakenly attributed to the front tire. However, one day when the bike was up on its center stand, I got on the ground behind it, gave the rear wheel a spin, and watched in fascination as the rim tracked straight but the tire itself wobbled like a drunken bum. So, I installed a new Dunlop Elite 4 on the back (which I spun after installation just to make sure it ran true), and instantly my fuel mileage increased from 21 MPG to 33 MPG. And the replacement got rid of the cornering growl that is so common on this bike. I guess replacing the wobbling rear tire either reduced the amount of resistance the tire was providing on the bike or reduced the surface travel area of the tire itself. Who knows. But color me happy, and also let me thank you folks for your suggested fixes.

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Re: Poor Gas Mileage on my 1990 SE

Post by Bluewaterhooker0 » Fri May 18, 2018 11:25 pm

That's fascinating. I don't think I've ever heard of mileage being effected to that extent due to tire/s. Are you sure that nothing else has changed, like overall general temperatures ? Interesting info, if accurate.

garywyoung
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Re: Poor Gas Mileage on my 1990 SE

Post by garywyoung » Sat May 19, 2018 9:01 am

Sure, it’s generally warmer, but after someone on the forum had suggested that the cold enrichment circuit is a gas hog, I’d been very stingy in my use of it during winter rides, but doing so had no real effect.



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