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Main Area => General GS500 Discussion => Topic started by: dadsafrantic on July 25, 2009, 06:12:59 PM

Title: mpg serious decrease...whats my problem?
Post by: dadsafrantic on July 25, 2009, 06:12:59 PM
also have been pouring in the oil as well.  a pint in the last 2200 miles.  i have gone from 52-54 or more mpg to 47 on the last tank.  yikes.  i might as well ride a chevy with that kind of mileage.

:dunno_white:
Title: Re: mpg serious decrease...whats my problem?
Post by: KasbeKZ on July 25, 2009, 06:23:49 PM
how many miles are on your bike? sounds like it might just be worn out!

or you left the e-brake on. check that! :)
Title: Re: mpg serious decrease...whats my problem?
Post by: Bridger on July 25, 2009, 07:42:40 PM
no e brake on a gs man.
Title: Re: mpg serious decrease...whats my problem?
Post by: Toogoofy317 on July 25, 2009, 08:12:39 PM
Yeah without more info about the bike it is hard to tell. I mean how long between oil changes, valve check, how's the petcock. Lots and lots of possibilities!

Mary
Title: Re: mpg serious decrease...whats my problem?
Post by: jrains89 on July 25, 2009, 08:57:22 PM
you realize that 47mpg is still really good in town right? that's right where a gs should be.
Title: Re: mpg serious decrease...whats my problem?
Post by: redhenracing2 on July 25, 2009, 10:12:46 PM
uumm dude I wish i got half the mileage that you did.

look down there

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Title: Re: mpg serious decrease...whats my problem?
Post by: average on July 25, 2009, 10:38:22 PM
Red, if that's your true mileage than you have some serious issues going on with your gs.  :icon_confused:
Title: Re: mpg serious decrease...whats my problem?
Post by: jrains89 on July 25, 2009, 10:58:18 PM
so i just re-read this and realized that you never said anything about that being in town, for all i know it could be highway. and if it's all highway, that sucks, i get 65mpg highway.
Title: Re: mpg serious decrease...whats my problem?
Post by: KasbeKZ on July 26, 2009, 03:20:18 AM
yeah the e-brake was a big joke! just ribbin'!

what is all this about appropriate mileage? ever since i've been on here all i've heard about was 50-70 depending on age and how you drove. even with extensive mods i've  never heard of a gs getting below high 40's, and he doesn't seem to be modded. let's not forget that the bad mileage and the oil burning/leaking started at the same time. there must be something actually wrong, because drastic changes like that should not be happening out of no where.
Title: Re: mpg serious decrease...whats my problem?
Post by: joshr08 on July 26, 2009, 05:01:03 AM
is it leaking or burning the oil?  trick question because every motor in the world gs500 or not burns oil......most motors just make enough condinsation to compinsate for the burnt oil.  but really with not much info to go on here theres not much anyone could really tell you on your poor fuel mileage other then a few things to check unless you give some more info.

things to check

sticking caliper
sticking float
running to rich
stuck choke
chain slack
slipping clutch
Title: Re: mpg serious decrease...whats my problem?
Post by: Skeets on July 26, 2009, 05:04:07 AM
I get 40 mpg...town..shifting at 9k
Title: Re: mpg serious decrease...whats my problem?
Post by: dadsafrantic on July 26, 2009, 09:02:37 AM
ok, more information.

i have 42.5k on the bike.  more riding is about 65 miles per day freeway and 7 or so miles city.  the oils does not leak out.  i have a fresh chain (the mpg was fine for the first 1500 miles and the slack is right so i don't think it is the chain) and the calipers do not rub.

the throttle response seems the same so i don'tm think the floats are sticking.

the clutch may be an issue because the bike did a strange slip thing going onto the freeway the other day.

uh, the valves have been about 20k since the last adjustment.
Title: Re: mpg serious decrease...whats my problem?
Post by: joshr08 on July 26, 2009, 09:48:09 AM
have you noticed higher rpm's for same speed if so you may need an adjustment or new clutch also your way over on valve check atleast.
Title: Re: mpg serious decrease...whats my problem?
Post by: DoD#i on July 26, 2009, 10:10:04 AM
Someone last year had a mysterious milage decrease which turned out to be a valve way out of whack.

So check those.

Red hen must have some major issues - my 4,900cc 6000lb truck gets those kind of numbers...
Title: Re: mpg serious decrease...whats my problem?
Post by: sledge on July 26, 2009, 10:34:42 AM
S**t in your air-filter!
Not suggesting you actually defecate in there, just check it and make sure its not blocked.

Title: Re: mpg serious decrease...whats my problem?
Post by: KasbeKZ on July 26, 2009, 11:19:43 AM
20k is a pretty long time to go without checking those valves. it would be a good idea.
Title: Re: mpg serious decrease...whats my problem?
Post by: redhenracing2 on July 26, 2009, 11:49:43 AM
Quote from: average on July 25, 2009, 10:38:22 PM
Red, if that's your true mileage than you have some serious issues going on with your gs.  :icon_confused:
Yeah my left cylinder doesnt fire below 6k rpms . . . .
Title: Re: mpg serious decrease...whats my problem?
Post by: average on July 26, 2009, 12:07:37 PM
Low compression, bad coil? :icon_confused: :dunno_black:
Title: Re: mpg serious decrease...whats my problem?
Post by: redhenracing2 on July 26, 2009, 12:50:28 PM
Quote from: average on July 26, 2009, 12:07:37 PM
Low compression, bad coil? :icon_confused: :dunno_black:
I replaced the coils a while back and it didnt change anything. I swapped the cables back and forth too and it stayed with the left cylinder. It's probably a compression issue but I haven't had it checked, mainly because I am a cheapass and the shop wants 30 bucks to do it.
Title: Re: mpg serious decrease...whats my problem?
Post by: KasbeKZ on July 26, 2009, 05:10:49 PM
you can get your own gauge for less than that.
Title: Re: mpg serious decrease...whats my problem?
Post by: gsJack on July 26, 2009, 05:52:19 PM
Quote from: redhenracing2 on July 26, 2009, 12:50:28 PM
Quote from: average on July 26, 2009, 12:07:37 PM
Low compression, bad coil? :icon_confused: :dunno_black:
I replaced the coils a while back and it didnt change anything. I swapped the cables back and forth too and it stayed with the left cylinder. It's probably a compression issue but I haven't had it checked, mainly because I am a cheapass and the shop wants 30 bucks to do it.

No need for a gauge to check to see if it's a valve problem.  Finger in the hole test will tell you.  Check cold compression, valve clearance increases as engine warms.  Pull plugs, tie clutch lever to grip to engage switch, crank engine with one hand while firmly covering a spark plug hole with a finger of the other hand.  Finger will be blown away from plug hole with a loud pop as you crank engine if you have compression.  Pop should be about the same for both cylinders..
Title: Re: mpg serious decrease...whats my problem?
Post by: redhenracing2 on July 26, 2009, 09:42:20 PM
Quote from: gsJack on July 26, 2009, 05:52:19 PM
Finger in the hole test will tell you.
I have NEVER heard of someone doing this, but it sounds just logical enough for me to try it. Thanks pal  :thumb:
Title: Re: mpg serious decrease...whats my problem?
Post by: Dr.Sparkie on July 26, 2009, 10:15:34 PM
whoa whoa whoa whoa..... remember that the throttle has to be WIDE OPEN before you do this test.

otherwise your finger will be pulled into the plug hole... you might just get a hickey, or it might be a bit more painful.
Title: Re: mpg serious decrease...whats my problem?
Post by: sledge on July 27, 2009, 02:46:57 AM
How to make a cheap go/no-go compression tester.......

Take an old sparkplug
Break the ceramic off leaving a hole all the way through it
Screw into the engine.
Stretch a baloon over the broken end of the plug.
Turn the engine over by hand ..............and see what happens  :thumb:
Title: Re: mpg serious decrease...whats my problem?
Post by: gsJack on July 27, 2009, 06:59:26 AM
Quote from: Dr.Sparkie on July 26, 2009, 10:15:34 PM
whoa whoa whoa whoa..... remember that the throttle has to be WIDE OPEN before you do this test.

otherwise your finger will be pulled into the plug hole... you might just get a hickey, or it might be a bit more painful.

I've used the finger in the hole compression test on bikes many, many times over the past 25 riding years and still have 10 fingers.  Could be my 77 year old fingers are much tougher than yours.   :icon_lol:  I can hardly remember what a hickey anywhere is.

As with checking compression with a guage, holding the throttle wide open gives a better reading or louder pop but it works either way.  I tend to crack the throttle some as I grab the right grip to hit the starter button I think but it's no big deal either way.  Try it, you'll like it.   :thumb:
Title: Re: mpg serious decrease...whats my problem?
Post by: Alphamazing on July 27, 2009, 07:19:31 AM
20k since a valve adjustment? What about a valve check? Either way, get those valves checked!

Also make sure that one of the fuel lines leading from your petcock to your carbs isn't cracked/ripped and leaking fuel ever so slowly. Had that happen to me, and I saw a pretty significant dip in my fuel mileage.
Title: Re: mpg serious decrease...whats my problem?
Post by: dadsafrantic on July 27, 2009, 09:34:19 AM
Quote from: Alphamazing on July 27, 2009, 07:19:31 AM
20k since a valve adjustment? What about a valve check? Either way, get those valves checked!

Also make sure that one of the fuel lines leading from your petcock to your carbs isn't cracked/ripped and leaking fuel ever so slowly. Had that happen to me, and I saw a pretty significant dip in my fuel mileage.


It would be the valve check actually.  I did replace the fuel lines about a year ago when i had the last valve check.  I will look again.