gas mileage

[Roy]

Hello, all. I'm trying to figure out if my recently bought '77 GS550 is getting the gas mileage that it should. It gets 33, as checked with about three fillups, consistently, and I would describe my riding style as sedate, with only rare episodes of full on acceleration.

I don't know if it is running "right," as I really don't have anything to compare it to. It is smooth (relatively) and pulls OK at low RPM, say, from about 3,000 on in the higher gears, and when wound out it seems to have an OK "surge" of horsepower (I realize it's only 49 bhp.)

I think it turns about 3,000 RPM in 6th at 45 mph. I haven't counted the teeth on the sprockets. It doesn't seem excessively low-geared. It's low enough that with a little care I could start from a stop in 2nd gear, and I routinely turn corners in 2nd gear.

I thought it was running a little rich, since the exhaust pipes were sooty, and black, so I checked the air filter, which looked sort of dirty, but not excessive. I cleaned that all out, but I haven't checked the mileage since then.

My question is, shouldn't I be getting better than 33 mpg? Also, I can't find the factory stock tooth count on these, to compare mine to. Does anybody know what it was designed to have, and have many of you changed sprockets?

I'm using "premium" unleaded because where I buy, the regular has ethanol in it, and I already know from my car that that cuts the gas mileage down measurably.

Any help/advise/reality check/ would be appreciated. Thanks.

[btbarb]

A bit of search says anywhere from high thirties, mid fourties without much trying, some get even higher.

Here's a couple of threads from a "GS550 Mileage" search:

Thread 197405

Thread 141047


Sprockets are routinely changed when the chain is replaced, otherwise the chain wears out too fast, some change the gearing, some don't, personal preference.

Sorry no info from me on sprocket tooth counts.

[Jedz123]

Welcome to the forum!

Go through Bass Cliffs Mega Welcome. He usually will give you one . These bikes are +30 years old so many parts may need replacement. On A 550 45-50mpg is attainable. I got upper 30's low 40's on mine and thats riding like I stole it and bring the revs to redline often. Most of these machines haven't been properly taken care of in the last couple of decades so be thorough and go through everything on the Mega welcome. My GS750 when ridden gingerly gets 45mpg no issue...

Oil, bad wheel bearings, dragging brakes, dirty Carbs, not adjusted valves, weak spark... Etc list goes on what it could be. Just take the time to go through it entirely. These bikes when brought back to 100% will go for tens of thousands of miles with no issues.

Good luck, welcome

[Roy]

Thanks for the info! I did find fuelly.com which seems to have a pretty large database for mileage on most bikes, and my 33 mpg isn't all that out of line among the other fuelly participants with GS550s.

[bbjumper]

Doesn't sound right to me, my 850 gets mid 40's.

Just sayin

[Steve]

I see several things going on here.

Hello, all. I'm trying to figure out if my recently bought '77 GS550 is getting the gas mileage that it should. It gets 33, as checked with about three fillups, consistently, and I would describe my riding style as sedate, with only rare episodes of full on acceleration.

Depending on your definition of "sedate", you might be lugging the engine. That little engine needs to spin a bit faster to keep in in its efficient range.

I don't know if it is running "right," as I really don't have anything to compare it to. It is smooth (relatively) and pulls OK at low RPM, say, from about 3,000 on in the higher gears, and when wound out it seems to have an OK "surge" of horsepower (I realize it's only 49 bhp.)

How long have you had this bike? Do you know anything of its history? Have you done any of the basic maintenance that is REQUIRED?

I think it turns about 3,000 RPM in 6th at 45 mph. I haven't counted the teeth on the sprockets. It doesn't seem excessively low-geared. It's low enough that with a little care I could start from a stop in 2nd gear, and I routinely turn corners in 2nd gear.

Save your clutch, don't start in second gear.

Here is a cut-and-paste from the factory service manual. Look at the "final reduction", it shows your sprocket tooth counts.

I thought it was running a little rich, since the exhaust pipes were sooty, and black, so I checked the air filter, which looked sort of dirty, but not excessive. I cleaned that all out, but I haven't checked the mileage since then.

A dirty air filter might be part of the problem, but I'll bet that dirty carbs are even more of a problem. There is a procedure to clean them and replace the o-rings that just might do wonders for you.

My question is, shouldn't I be getting better than 33 mpg? Also, I can't find the factory stock tooth count on these, to compare mine to. Does anybody know what it was designed to have, and have many of you changed sprockets?

Yes, you should. See my comment above, it shows info from the factory manual.

I'm using "premium" unleaded because where I buy, the regular has ethanol in it, and I already know from my car that that cuts the gas mileage down measurably.

Yeah, gas with ethanol will drop your mileage a bit, but not as much as using "premium" gas when it's not necessary. Try using "regular" gas, even though it has ethanol in it, see if your mileage improves a bit.

There are many threads on the topic, but "premium" gas does not mean it's any better, only that it's higher OCTANE. Octane is not "power", it's a measure of resistance to detonation that is caused by sources other than the spark plug. Higher octane is needed in higher-compression engines because the higher compression puts more heat into the mixture, sometimes to the point of ignition. That ignition before the spark is what is known as "pinging" or "knocking", and is bad for the engine. "Premium" gas is harder to ignite and burns slower, so ignition timing needs to be advanced to compensate, so that the mixture is completely burned at the proper time in the crank's rotation. Add in the fact that "premium" gas has fewer BTUs per gallon (that's LESS ENERGY), you can see that it's really NOT all that "premium", except for the price.



Where are you on this little blue marble? One of us might be close enough to lend you a hand. May I suggest adding your location to your profile (use the User CP link in the upper left corner of this page), and also add a short signature that mentions your bike, so you don't have to remember to mention what it is every time you ask a question about it. No need for an actual address, or even a town, if you don't want. After all, my own location, "southwest oHIo" is a rather large area.

.

[Roy]

Steve, thanks for the information-rich response. I'm hoping the now-clean air filter will improve the mileage some, and you are right--I am probably guilty of running the engine in an RPM range below it's best efficiency--not so as to actually lug it, but as you say it takes a pretty good amount of throttle to get a little acceleration down there. But, the longer I have this bike, the less afraid I am that I will accidentally blow up the engine. With this in mind, I'll hold off on putting a bigger sprocket in front until I think I have everything else sorted out.

I also want to try a tank of regular. I wish I could find some without ethanol, though.

[gearhead13]

Dont worry about blowing it up, as I have heard those 550's are pretty bulletproof, with a roller crank as well IIRC

[Roy]

You may want to add you location and bike in your signature for future reference, and you can google fuel stations with only gas and no ethanol, it will give locations in your area if there are some.

Thanks for the info. I'm trying out my signature now.

[BassCliff]

Hi,

I get low to high 40s depending on conditions and habits. I would think that you could do at least as well. Has all the maintenance been properly done? See the links in my sig for more information. Or New Members, CLICK HERE!!


Thank you for your indulgence,

BassCliff

[Roy]

Hi,

I get low to high 40s depending on conditions and habits. I would think that you could do at least as well. Has all the maintenance been properly done? See the links in my sig for more information. Or New Members, CLICK HERE!!


Thank you for your indulgence,

BassCliff

I am going to run a couple tanks of gas and check it again. I think it runs so much better with the air filter cleaned out, and I have been running it in a little higher RPM range--where it actually has some power--this may help quite a bit.
I'm thinking the smaller displacement isn't really the advantage you would think because it may be working a little harder than it's bigger brothers.

[Toasty]

For better gas mileage you need to keep the rpms up, it seems counter productive but it works. If you're cruising below 5500 rpms you're lugging it. I was getting 48-55 mpg on my 81 550 before I tore it down.

[Steve]

I also want to try a tank of regular. I wish I could find some without ethanol, though.

On one of my work assignments down South, I was able to get some ethanol-free gas on a regular basis, so I tried it. Granted, this was in my van, but gas is gas, right?

Keep in mind that I keep a logbook for all the gas that goes into the van. I made notes to show which tanks had the ethanol-free gas. I could not see ANY difference in gas mileage, certainly not nearly enough to offset the twenty cent increase in price.

I have also had the occasional opportunity to use ethanol-free gas in my bikes, but nothing on a regular basis. I don't keep logbooks for the bikes, so just did the quick calculation for those tankfuls and did not see any real improvement.

Bottom line? I don't think that my vehicles care what they get to drink, as long as there is plenty of it.

Either that, or I am just to insensitive to notice any difference.

.

[Roy]

On one of my work assignments down South, I was able to get some ethanol-free gas on a regular basis, so I tried it. Granted, this was in my van, but gas is gas, right?

Keep in mind that I keep a logbook for all the gas that goes into the van. I made notes to show which tanks had the ethanol-free gas. I could not see ANY difference in gas mileage, certainly not nearly enough to offset the twenty cent increase in price.

I have also had the occasional opportunity to use ethanol-free gas in my bikes, but nothing on a regular basis. I don't keep logbooks for the bikes, so just did the quick calculation for those tankfuls and did not see any real improvement.

Bottom line? I don't think that my vehicles care what they get to drink, as long as there is plenty of it.

Either that, or I am just to insensitive to notice any difference.

.

That's interesting. My similar experience with a car was to switch from regular unleaded E-10 to "premium" w/out ethanol, and my in-town gas mileage went from 26 to 31, average, with about five tanks. The difference may have been I went to a higher octane rating at the same time I switched off of ethanol, (although this is not what people are saying would happen) plus my car might have responded differently. than yours. (A very small 4 in a Honda Civic.) I guess that's what they mean by "your mileage may vary."