Best speed/rpm for fuel economy? GS850

[Burque73]

Speaking of tank volume, I'll never forget this post by 2BRacing showing a massive 28L tank on a GS1000

https://www.thegsresources.com/_forum/showthread.php?250880-Suzuki-s-in-the-family&highlight=

 

[Gorminrider]

Now THAT ^^^ is a cruising bike!

 

[zuluwiz]

My 850 is as stock as I can make it, and on a 140-mile(each way) trip 1.5 years ago, I was usually running 4k rpm and getting 43 mpg. That gives me 60 mph. That's loafing for the 850, but I'm not the speed demon I was 40 years ago.

 

[93Bandit]

The book says it's 22L, but on more than one occasion I've put in 24L when it was running on reserve for a while and I'd hoped to find a petrol station soon.
I suspect the book is being conservative, but that 22L figure is repeated all over the various spec pages on the web and even in the Haynes manual.
Whether Suzuki ever made the tanks a couple of litres larger for the EU market - I doubt if it was worth their while to go to all that extra hassle just for us, so nah.
Otoh, in the early days of having both bikes, the first thing I did was to enlarge the stupidly small breather hole at the top of the filler neck, and that allows a bit extra fuel in with a rapid fill, so perhaps that's it. I suspect the 22L figure is to allow sufficient headspace for expansion in the desert, etc. Not a problem for me, as there are no deserts here, and I always have a journey after filling, even if it's just the journey home, so the bike is never parked up with a totally full tank, there's always a little headspace in it.

22L? That's 5.8 gallons. That's a lot bigger than mine. Is the GL tank smaller than the G tank? Honestly I don't understand all the differences. The GL tank is more tear drop shaped, and the G tank is more rectangular. I assume the G tank is bigger? Can someone clarify? If you include pictures too, you'd be extra cool.

 

[Steve]

22L? That's 5.8 gallons. That's a lot bigger than mine. Is the GL tank smaller than the G tank? Honestly I don't understand all the differences. The GL tank is more tear drop shaped, and the G tank is more rectangular. I assume the G tank is bigger? Can someone clarify? If you include pictures too, you'd be extra cool.

Yes, the GL tank is smaller. It is 4.5 gallons. It will be the same as my wife's '82 850L.

Your '81 850G does have a 5.8 gallon tank. The two tanks are NOT interchangeable.

This is one of the better pictures I have of her tank:

I don't have a decent picture that shows my 850 tank, but this is my son's 1000G, which is the same tank.

.

 

[93Bandit]

Thanks Steve, that's perfect. OK, so my suspicions were correct.

I wish the tanks were interchangeable. Is it just due to GL tank is two bolts, G is one? Or are there other differences as well?

 

[Rob S.]

Rest assured, I had BOTH hands on the grips. My wife leaned over my shoulder to get the picture.

.

I love your wife. I love you. But it goes without saying I hate the 85 mph speedo. I was only too glad to replace mine with the 140.

I remember when the KAW Z1 came out, it had a 160 speedo. I recall some dufus who thought it would go that fast. Darn near broke my heart to break the truth to him.

 

[Steve]

I wish the tanks were interchangeable. Is it just due to GL tank is two bolts, G is one? Or are there other differences as well?

The '79-'81G models and the '80 L have a single horizontal bolt at the back. The '82/'82 G and the '81-'83 L have two vertical bolts at the rear.

Besides that, the L tanks are shorter from front to rear, so the front mounting points on the frame are a couple of inches farther back and there are plastic covers to hide the exposed frame. The reason the tank is shorter is because of the forks. :-k To give that extended "chopper-esque" look, Suzuki straightened out the angle on the triple clamps and moved the forks behind the axle (this left the axle just about exactly where it was before). Now that the forks were behind the axle, they could extend them for "the look". Now that the fork tubes are farther back, they would hit the tank when the forks were turned to full lock. Shortening the tank gave them the room to do that. It also allowed the opportunity to do their version of a "peanut" tank that was popular on choppers. The stepped seat, chrome fenders and the shorter, megaphone mufflers completed the "chopper" look.

Mechancially, the Ls are virtually the same as the Gs, but ergonomically, they SUCK.
Unless you happen to be that ONE individual that happens to fit.

.

 

[bwringer]

I just dropped in to say that generally, if you're worried about fuel economy on a motorcycle, you're doing it wrong...



Anyway, you can happily flog an 850 at 6,000+ RPM for hours and hours on end. I've done it many times because I live a long way from the mountains. These engines love to rev, they need to rev. Grip it and rip it. It won't hurt a thing. Learn to love that groovy rush between 6,000 rpm and redline. You wanna putt around like an old lady, buy a Harley or a lawn tractor. Spin to win.

However, a motorcycle with a rider on top is an aerodynamic disaster, with stuff sticking out all over and a coefficient of drag resembling a brick. Worse, probably.

So fuel economy on a motorcycle mostly varies with average airspeed. Other factors like RPM and acceleration rates make very little real-world difference. Drag varies with the square of speed (it's not linear), so there's a big difference between, say, 70mph and 80mph.

To put it another way, drag at 85mph is about double the drag at 60mph.

 

[93Bandit]

The '79-'81G models and the '80 L have a single horizontal bolt at the back. The '82/'82 G and the '81-'83 L have two vertical bolts at the rear.

Besides that, the L tanks are shorter from front to rear, so the front mounting points on the frame are a couple of inches farther back and there are plastic covers to hide the exposed frame. The reason the tank is shorter is because of the forks. :-k To give that extended "chopper-esque" look, Suzuki straightened out the angle on the triple clamps and moved the forks behind the axle (this left the axle just about exactly where it was before). Now that the forks were behind the axle, they could extend them for "the look". Now that the fork tubes are farther back, they would hit the tank when the forks were turned to full lock. Shortening the tank gave them the room to do that. It also allowed the opportunity to do their version of a "peanut" tank that was popular on choppers. The stepped seat, chrome fenders and the shorter, megaphone mufflers completed the "chopper" look.

Mechancially, the Ls are virtually the same as the Gs, but ergonomically, they SUCK.
Unless you happen to be that ONE individual that happens to fit.

.

So based off of this information and some other info I've gathered, I'm doing this all backwards... I should use my G as my crusier and L as a cafe racer. The problem with that is my L is in far better condition than my G and I'd hate to ruin it. My G is so far gone it'll either remain a parts bike and soon decay into rust and uselessness, or I can attempt to revive it into something I would enjoy. If only I could put a larger tank on my L.

Do you think with some ingenuity and a welder the G tank could be retrofitted to my L and turn out half way decent?
Using the front mounting point to avoid fork contact? Although I suspect I'd have seat problems then since the tank is longer... Hmm....

I haven't ridden many bikes so I don't really have a good perspective on what good ergonomical bike feels like vs. what a bad bike feels like. So I don't really have any issues with my L. I've never ridden for more than an hour though so I haven't truly tested it yet.

 

[Burque73]

A friend and (former?) GSR member named Raygun put a G tank on his 1100L. Search for posts by him. Maybe he wrote something up about it.

 

[Rob S.]

I just dropped in to say that generally, if you're worried about fuel economy on a motorcycle, you're doing it wrong...

Anyway, you can happily flog an 850 at 6,000+ RPM for hours and hours on end. I've done it many times because I live a long way from the mountains. These engines love to rev, they need to rev. Grip it and rip it. It won't hurt a thing. Learn to love that groovy rush between 6,000 rpm and redline.

However, a motorcycle with a rider on top is an aerodynamic disaster,

Here, here!

In the third world, they ride motorbikes for economy. Here, we ride bikes because they're cool. You meet the nicest people...

But I grew up slightly priveledged. I also grew up when gas was less than a buck. I recall 35 cents a gallon.

I remember once sitting in the family's station wagon, a 1966 Oldsmobile Vista Cruiser. Dad put her in Park and said he'd be right back, he had to get something from our 6th floor apartment.

"You're going to leave it running?" I asked. "Won't that waste a lot of gas?"

"No," he told me. "It'll use more gas to restart it." So my die was cast.

Every time I've brought a vehicle in for work, I've told the mechanic, "Fuel economy doesn't matter. If you can make it a hair faster, I don't care if it uses twice the gas."

And about revving it? My biggest fear is that my little brothers will die before they experience a big bore Jap four near redline.

 

[Burque73]

Here's the thread I was referring to.
https://www.thegsresources.com/_forum/showthread.php?239742-G-tank-on-my-L
Apparently the G tank, triple clamp and forks were taken from a parts bike. I remember Raygun saying he used a length of allthread through the frame and fabricated some rubber nubs on the ends for the tank mounts.

 

[Steve]

If only I could put a larger tank on my L.

Do you think with some ingenuity and a welder the G tank could be retrofitted to my L and turn out half way decent?
Using the front mounting point to avoid fork contact? Although I suspect I'd have seat problems then since the tank is longer... Hmm....

A friend and (former?) GSR member named Raygun put a G tank on his 1100L. Search for posts by him. Maybe he wrote something up about it.

I have not read through Raygun's post, but about the only way to get things to play together would be to fabricate your front mounts (you can see where they would be on your L frame) and put the tank in place. To keep the forks from hitting, you would need to replace the forks and triple clamps with parts from a G.

There might be a slight fitment issue at the seat/tank interface, but it shouldn't be too bad. I would have to take the seat off my wife's L and place it on my frame to see how (if?) the angles match.

.

 

[93Bandit]

Here's the thread I was referring to.
https://www.thegsresources.com/_forum/showthread.php?239742-G-tank-on-my-L
Apparently the G tank, triple clamp and forks were taken from a parts bike. I remember Raygun saying he used a length of allthread through the frame and fabricated some rubber nubs on the ends for the tank mounts.

Thanks for the link! I'll have to look at both my bikes to see what it would take to do the swap.

I have not read through Raygun's post, but about the only way to get things to play together would be to fabricate your front mounts (you can see where they would be on your L frame) and put the tank in place. To keep the forks from hitting, you would need to replace the forks and triple clamps with parts from a G.

There might be a slight fitment issue at the seat/tank interface, but it shouldn't be too bad. I would have to take the seat off my wife's L and place it on my frame to see how (if?) the angles match.

.

I think I have all the parts I would need. I hate tearing up my L though. I finally got it running and would like to enjoy this season. We'll see.

 

[raygun]

So I suppose I'll resurrect my account for this. Just to prove the naysayers wrong, you can and I did put a G tank on my L. It fit pretty well actually. The front required cutting off the existing mounts for the tank (where the rubber bumpers sit) and either relocating those mounts up the neck with a welder or using a piece of allthread, nuts, and washers to make up new mounts. The rear was the simplest, I think I used a piece of chain to pull the tank down onto the frame and put a piece of rubber between the frame and tank. I think someone with more ability, creativity, and tools could fabricate up a bracket. I no longer have the bike nearby but still own it. I'll try and get some pictures and measurements when I get a chance but for now I've got some very crude drawings that might help. I personally believe this is a very simple modification and possibly reversible with a welder. Of course, you will have to use the G forks and triple clamp. I don't remember about the wheel and the bracket for the brakes. I ended up using the G wheels I had because I liked them better. I didn't want my bike to be out of commission so I rebuilt the G forks and got everything ready for the swap which I did in one day. The bike was a 1982 GS1100GL and the donor bike was a 1980 GS850G. Sorry for the super large images. I have no idea how to resize.

 

[Steve]

Raygun, nice to see you drop in. :encouragement:

I see that you have an '80/'81 G tank on your '81 L. I see now why you had to use a chain on the rear mount. The G tank uses a single horizontal bolt, the L uses two vertical bolts.

I am wondering if it would be possible to bolt an angle bracket to the L frame locations that would have provision for the bolt on the G tank. Maybe even reverse the hardware. Use that vertical tab to capture a bolt that is being used more like a stud. Slide the tank onto it from the rear, then use a washer and nut to hole it there. :-k

.

 

[raygun]

I think it would definitely be possible with the right tools and skills. I didn't have either at the time (and probably still don't). I do understand that 93Bandit would hate to take apart a running motorcycle but with some careful planning and preparation, I think the whole swap could be done in an afternoon. I think I also had to enlarge the holes for the fender to get it to fit.

 

[93Bandit]

I think it would definitely be possible with the right tools and skills. I didn't have either at the time (and probably still don't). I do understand that 93Bandit would hate to take apart a running motorcycle but with some careful planning and preparation, I think the whole swap could be done in an afternoon. I think I also had to enlarge the holes for the fender to get it to fit.

Hey, thanks for adding to the thread! I like your idea of getting everything ready for the swap beforehand. That would definitely reduce down time.

 

[raygun]

Hey, thanks for adding to the thread! I like your idea of getting everything ready for the swap beforehand. That would definitely reduce down time.

Not a problem. I'll try and get some pictures of the bike when I get a chance. If you need any help, feel free to get my contact information from Burque73.