Super Low MPG

[Nessism]

How about adjusting the valves? If the valves haven't been adjusted you could be losing compression and fighting a losing cause with poor thermal efficiency. Not to mention the valves and seats will burn if they are leaking. Adjusting the valves and checking compression would be a useful test.

[Steve]

Big T - Is there something else I should call cleaning them with carb cleaner? Spray-cleaning?
I recognize that it's not a full clean like a strip n' dip.

Most of that will depend on how (much) you are spraying with carb cleaner. If you are just spraying the outside, it's just a waste of spray. If you are dropping the bowls and spraying what you can see, it's also a waste of spray. Just out of curiosity, ... how many cans of spray did you use per "cleaning"? I have heard of some guys using two or three cans per "cleaning". For reference, I use a bit of spray after dipping a set of carbs, and can usually get three sets of carbs per can.

I'm shifting around 6k so I'm cruising around 4k mostly. Is that high? Where do you live in the rev range?

Keep in mind that I'm on old geezer on a full touring bike.
Just commuting in town, the engine seldom sees over 4k, it's not uncommon to shift at 3.5k. If something a bit more "exuberant" is called for, I'll raise the shift point to about 5 or 6k. Yeah, it's been to 8k more than a few times, but the 850 engine doesn't have much of an increase over that, so it very seldom sees redline.

You were mentioning earlier (post #3) how your fuel screws were turned out one full turn. That is a bit rich, and will be most-noticeable at low-throttle openings. Running 6-8k in second and third gears is definitely "low-throttle", so you are spending a LOT of time in your super-rich jetting. I did not see it specifically mentioned, but I get the impression that you have a K&N filter in a stock airbox, along with stock exhaust. If that is true, you should have stock jetting (hopefully not plugged up or drilled out). The fuel screw should probably be about 5/8-3/4 turn out from LIGHTLY seated. The air screw will have to be tuned to match, I would start with 1 turn out, then turn out slowly to achieve best idle. Might end up in the 1 1/4 turn area.

Higher engine speeds are absolutely no problem when there is a bit of load. My wife leaned over my shoulder and snapped this while chasing some other GSers on a rally almost 10 years ago.



Yep, it's a full-blown touring bike. Loaded with 'stuff' for a weekend and ridden two-up, we averaged about 41 mpg on a three-day weekend through New England. You should be approaching those numbers yourself.



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[mattd1205]

mattd1205 - Yeah I'm gonna spin them back out a little. I think maybe I was mislead from the previous owner having richened it up to compensate for a few little air leaks? We'll see if that helps. I've never heard of a colortune but they're cheap enough. I'll pick one up and see what that does.

Big T - Is there something else I should call cleaning them with carb cleaner? Spray-cleaning? I recognize that it's not a full clean like a strip n' dip. I have read everything a few times. It's had this kind of MPG since I bought it about half a year ago. I've swapped the ignition to a dyna, replaced the regulator/rectifier (but not the stator), swapped the air filter, and worked on the carbs (replaced the boots and o-rings, synched them, had a professional synch them, sprayed them with cleaner). I've also replaced the headlight a couple of time and the socket once because it caught on fire.

Steve - I'm shifting around 6k so I'm cruising around 4k mostly. Is that high? Where do you live in the rev range?

If theres airleaks any carb tuning will be pointless. It’s very easy to get these bikes air tight. Check for air leaks on a the intake side with carb spray and check your exhaust for any leaks. I pressurize my exhaust with a shop vac in the blower mode (after making sure the shop vac is clean) and spray soapy water on all the joints. People don’t like this method for some reason but I’ve never had a problem doing it over the years.

[Big T]

You should call it wasting time and money.
Just puzzled, cause if you bothered to pull the fuel and air screws you were half way there

[Rob S.]

...when I'm riding around town sometimes I'll rev up to 8k before shifting, but usually around 6. I spend a lot of time in second or third. I don't drive SUPER gently, but I don't rip around like a madman either.

But you always want to be ready to get mad at the drop of a hat, correct? (Me too.) I ride my 11E once or twice a month, rarely much more than 20 miles, but I always rev to 8, closer to 9 even (my redline) in a low gear (1st), or gears (1st and then 2nd), at least once every ride. Why? Just because. And come third gear, well, I've got to back off, because if I redline in third I'll be doing the buck (100 mph). And that I save for my 'special' time, the last few highway miles on the way home.

I may have a few cc's on you, but I know how quick 750cc, DOHC, in-line fours are. Especially Suzukis. So I suspect your low mileage starts with your right wrist. You sound like me (decades ago), 'standing tall before the man'.

"Your honor, I may not drive SUPER gently, but..."

"Looks to me like you don't drive gently at all. $600. And consider yourself lucky, because I'm supposed to suspend your license also. Now get out of here." BAM goes the gavel!

[Gorminrider]

It sounds to me that the bike is running pretty well. I don't have any reason to doubt your carb guy . You'd hope he'd notice irregularities from his own experience with the bikes. I've never seen huge results from any tweaking of mixture screws beyond the hope of a really smooth and clean idle. But then, I'm not so much at idle- a maximum of 6 stoplights in town and they're never all red... I've mentioned floatlevels and a stuck choke/enricher soo, I'll harp a little more on the calculation?

"As far as math - are y'all talking about the mpg math..I just put in how much I bought and my current mileage.

" Yes, mpg...Of course, and that should work fine. Need note however to confirm that the usual technique requires you to fill the tank each time... Then, with this baseline( a full tank) you can quickly check per
(A-B)/G=mpg
where A= latest odometer at fill-up
B=previous odometer at previous fill-up
G = latest gals to fillup...
(A-B) is therefore the miles travelled between fillups. Divide this by G (gas replaced to bring back to baseline= gas used per the miles it took the bike) and you get the correct result. I use the bottom of the filler neck in the tank and try to get very close to this each time.

PARTIAL fillups to no known "baseline" will give the wrong result*

...As an aside, this really is telling you about the previous fillup per quality of gasoline (I note the brand and type of gas) and terrain (mountains, or city, or prairie highway ) These will likely show up as different "averages".
Even periods where gasoline evaporates or leaks can show up in the results.

It might be convenient to add columns in your spreadsheet to note oil changes and maintenance notes too- it's handy if you're not doing it elsewhere.

* another method is an empty tank, pour in a the same quantity of gas each time and ride the bike until it stops-not practical or safe though.

[jimhickcox]

Because it's the easiest thing to get at and test I'm doing my fuel screws this afternoon. We'll see how that changes things.

Nessism - I haven't gone into the valves. I've always doing oil and basic maintenance but I'm still pretty new at really pulling things open, and like I (think) I said, this bike is my daily (I don't have a car). So while it's running well I'm trying not to create extra downtime. I'll get in there when I have a weekend and don't have to go anywhere though.

Steve - When I spray-clean, I pull the carbs, remove everything I know how to take off and soak all that in cleaner, spray out the inside surfaces a few times, and then reassemble. I know it's not ideal, but it's not a total waste of time and money because my needles were sticky and the bike was dribbling fuel, but now it's not. Also I'm not sure how much of the can I use, but I've done this at least three times to different bikes and I'm still on the same can. So not a ton?

I always feel like I'm mistreating the engine if I'm driving around at less than 3k - is that not lugging it a little? Maybe it's because I was riding a 550 daily for the last couple of years? That guy doesn't even start to pull until ~4k. But on that, a 550t with pods and no second gear, riding roughly the same way, I still averaged 33.41mpg over the last 5000 miles, which I feel like I ought to beat with my stock airbox and exhaust setup on this (and all of the gears).

mattd1205 - I checked for leaks and had some in the boots on both sides of my carbs, so I replaced them and they're good now.

Rob S - Where do I mail the payment check?

Gorminrider - Yeah, I asked him (my guy) about the mpg and he said everything was running well and he wouldn't know what to change. I do suspect it will benefit me to do a full teardown on the carbs when I can, and replace the gaskets and stuff. As far as the mileage, I'm pretty obsessive about how I'm filling the tank. I don't take notes on vendor/quality, but I do note when and various other things, and calculate miles per day, miles per gallon, and the day and mileage at which I do every service, so I can see what affects what and how.

[Steve]

I haven't gone into the valves. I've always doing oil and basic maintenance but I'm still pretty new at really pulling things open, ...

I'm sorry, but if you have not "gone into the valves", you have NOT been doing "basic maintenance".

I always feel like I'm mistreating the engine if I'm driving around at less than 3k - is that not lugging it a little? Maybe it's because I was riding a 550 daily for the last couple of years? That guy doesn't even start to pull until ~4k. But on that, a 550t with pods and no second gear, riding roughly the same way, I still averaged 33.41mpg over the last 5000 miles, which I feel like I ought to beat with my stock airbox and exhaust setup on this (and all of the gears).

Many years ago, I was taught that "lugging" an engine is when you can not accelerate while using the current gear. At lower engine speeds, you will also notice some chugging and bucking along with the lack of acceleration.

Yes, a 550 is notoriously low on power, especially below 4-5k. The fun on those is definitely above 6k.

If you averaged 33 mpg on a 550, you might want to check into calibrating the nut that holds the handlebars.
A 550 should regularly return over 50 mpg. If you flog it constantly, it will dip into the 40s, but 33???

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[rphillips]

Plug readings haven't been mentioned lately, unless I missed it. With the mpg. you're getting, your plugs should be black, wet & almost dripping fuel. If your plugs look OK, paper sack color, I'd look for gas getting out somewhere else, possibly overflow tubes, fuel line leak or something. When you're cleaning your carbs with aerosol cleaner, look close all inside the carbs, there are tiny holes in there. With the little straw on the spray tip, hold the straw on these little holes, sometimes ain't easy, but squirting cleaner in any hole, you should find cleaner squirting out the other end of that hole. none of the holes are dead end, every hole you squirt cleaner in, you should see the cleaner squirting out. I just don't see if your plugs look good, that much fuel can be going thru the cylinders. Just my opinion.

[Nessism]

Failing to adjust the valves will damage the engine; the clearance reduces with mileage and eventually the valves don't close so they burn, along with the seats. Shame on you. Hopefully the engine isn't damaged already.

[rphillips]

Yep, what he said about the valve adjust. It ain't hard, but it will do major damage if they are too tight, I have a CB1100 head out in the shop with 2 "burnt" valves, just cause I neglected checking them.

[Rob S.]

If you averaged 33 mpg on a 550, you might want to check into calibrating the nut that holds the handlebars.
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I'd appreciate if you'd call me Mister Nut.

[Steve]

I'd appreciate if you'd call me Mister Nut.

I have other names for you.

That comment was addressed to the original poster, jimhickcox.

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[jimhickcox]

Steve - The valves aren't due for an adjustment for another thousand miles (per the service manual and records). I'll get in there when it's time, and maybe before if I have the free time, but right now up-time is more crucial than cleaning up my MPG. And the 550 has seen some things - it's been a beater for a while, and it's jetted up to compensate for the pods someone put on it, but even Suzuki only specc'd it at 42mpg new, so mid-thirties on a guy who's had a rough life seems like an okay kind of low. Especially in the kind of traffic I ride in.

Nessism - I'll check the valves when they're due, don't worry. I'm not trying to ride this bike into the ground so soon after buying it.

Rphillips - Yeah, my insulator tips are pretty black all the way down, like you'd expect on a plug on a bike running real rich. Hopefully my misunderstanding about where the fuel screw should be at was the big issue and will get me back up where I want to be.

[Nessism]

How do you know when the valves were last adjusted? Do you have service records from the previous owner?