Poor mileage on my '82 GS650G

**Guest** · 08-10-2007, 10:48 PM

I had a 1982 GS650G which I rode 25,000 miles. For the first 7,000 milles or so I got about 42 mpg. Then the rings seated, and fuel consumption decreased. I was typically getting 55 mpg at roughly 65 mph. Translated to metric, that is very roughly 300 km/tank.

I'm far from an expert at diagnosis, but by first guess is that you're only firing on two cylinders, so half of the gasoline is going through the bike unburned. Very carefully move your hands close to the exhaust pipes to see if they're all heating up when the bike is running.

Tom

**slugsride** · 08-10-2007, 10:52 PM

Originally posted by teacherman

Hi Everyone!

This is my first post, so forgive any foolish questions.

I bought a 1982 GS650G this May, and after a little trouble, I finally have it working great!

According to the service manual I bought, my tank is about 12L. My one big problem is that I'm barely getting 110kms to the tank, and that's if I stretch it! The mileage is absolutely horrible! I don't ride it hard (I try not to go over 4,000 or 5,000 rpms), and I run premium gas.

Does anyone have any ideas about how to improve my mileage? Also, I was thinking of putting air pods in to replace my air box, will that improve my mileage? I have heard that if I install pods, I will have to get my carbs re-synched....is this true?

Thanks for all your help!

Sasha

An over-oiled air filter is a common problem. Check for dragging brakes and tight spots on the chain. Make sure the choke plungers close fully on all the carbs.

Pods are a lot of work, you have to re-jet and then re-synch. Do a search on posts by "Keith Krause" to get an idea of whats involved. Good luck!

**BassCliff** · 08-11-2007, 01:37 AM

Hey howdy hey!

Mr. teacherman,

Let it be known that on this day you are formally welcomed to the GSR Forums as a Junior Member in good standing with all the rights and privileges thereof. Note that "good standing" usually implies pictures. :-D

Many factors could cause decreased fuel economy. Besides those already mentioned I'll add checking valve clearances and ignition timing. What do your plugs look like? Are you running too rich? It's also possible that you've got a minuscule leak in a fuel line, one that spits out a vapor only while you're riding rather than dripping all the time. Do you have fresh gear oil in the rear differential? (Mr. slugsride didn't notice the "G" in your model number.) Make sure your airbox and the top of the air filter cage are sealed with new weatherstripping. There should be no air leaks in the intake, carb boots, O-rings, etc. If your cam chain has skipped a tooth it might run OK (sort of) but get lousy mileage.

Thanks for joining us. I'm just a baby here but there are lots of experienced, knowledgeable folks here who can solve any problem on this classic bikes.

Thank you for your indulgence,

BassCliff
(The unofficial GSR greeter)

**SqDancerLynn1** · 08-11-2007, 01:43 AM

The right wrist will play a big roll in gas milage. I would sugest, valve check, compression test and a GOOD carb sync as a start. Unless someone has been messing with it the timing should be fine

**txironhead** · 08-11-2007, 02:06 AM

If you go the pods route, then yes, you will need to rejet. And your mileage will more than likely decrease while your horsepower increases slightly.

**JTsGS650** · 08-13-2007, 10:03 AM

110kms = 68.3508 miles. Hmmm. I get about 100-110 miles per tank on my bike (I still need to do a complete rebuild of my carbs and tune for peak efficiency). All of the above suggestions are good. I'd also like to suggest checking the operation of your fuel petcock. If the diaphram is bad you might be losing some gas into your crankcase. Check your oil to see if it smells like gas and rebuild/replace your petcock as needed. Good luck.

**Steve** · 08-13-2007, 04:58 PM

The quickest and easiest way to better fuel efficiency is to use the proper fuel. Dump the "premium" and use "regular" gas.

It is not called "premium" because it's better. It's called "premium" because it has higher octane. Octane does not contain power. Octane resists detonation caused by compression temperatures. By design, "premium" is harder to light (that's why it resists detonation) and burns slower (that's why you have to advance the spark). In a standard engine (like most of our bikes), it will not finish burning completely before the piston is going down too fast for the burn to help. You lose a lot of power there.

I also have an '82 650L here. It usually goes 110-120 MILES before switching to reserve, then takes about 2.5 gallons to fill. Converted, that is about 175-190 kilometers, then about 9.5 litres to fill. That works out to 18.4-20 km/l.

Check your air filter, check your idle mixture screws, check everywhere else for air leaks, you should be able to do much better.

.

**sonicgroove** · 08-14-2007, 04:05 AM

I just went out on a long cruise today with my friend. I, too, am getting poor gas milage. based on my calculations, since my speedo doesn't work, I'm averaging about 30ish mpg. I would at least like to be hitting 50. I calculated this by filling up b4 the cruise and asked my friend to mark his milage. After about midway through the cruise I filled up again which was about 1.5 gals and asked my friend how many miles we traveled, 52, the just divied it by 1.5 and came to 34mpg. Is there anyone is SoCal who can help me out with carbs? I'm new to carbs but am willing to learn. I do have some technical know how just not regarding carbs. If you have a set of carbtune syncs and/or colortune I'd really appreciate it. :-D I'm in LA area.

-groovin

**BassCliff** · 08-14-2007, 09:51 AM

Hey howdy hey!

Mr. sonicgroove,

This is what is referred to as "hijacking a thread". But not to worry and nonetheless,...

Let it be known that on this day you too are welcomed to the GSR Forums as a Junior Member in good standing with all the rights and privileges thereof. Note that "good standing" usually implies pictures! :-D

I have yet to delve into my carbs as I am just a youngster GS rider, but I'm trying to learn fast. I just happened to pick up a NOS Colortune the other day, but I understand that it's good for pilot jet adjustment, not main jet. What kind of bike do you have? I ride an 850G and have started to build a small library of reference materials. Feel free to start your own thread in this tech section and PM me. Perhaps I can at least point you in the right direction. For some possible immediate relief, have you tried some Deep Creep in the carbs or Sea Foam in a tank of gas (for cleaning)? Is your airbox and air filter cage sealed (with new weather stripping) against air leaks? Check if you need a new air filter and don't over oil it. Marvel's Mystery Oil in the gas will also help lube those sticky carb parts, but don't use it at the same time as the Sea Foam.

Thanks for joining us. There are quite a few GS gurus here and everybody is eager to help us keep our classic bikes on the road. Stick around here and you will become a better mechanic and a better rider.

Thank you for your indulgence,

BassCliff
(The unofficial GSR greeter)

**jbs80106** · 08-14-2007, 09:52 AM

Not sure how it coorelates but....

In all my vehicles, Impala, H3 and the 650G, if I get gas from my nearest sources ($afeway) my mileage always goes down by some 10%. I suspect their using some sort of blended Ethanol which is require here in Colorado in the winter time, but they're using it year round (they don't tell you whats different in their gas).

I just put 'regular' in my bike, which here in Colorado is 82 Octane (mid-grade is 84 and premium is 89 I think) which is all off by 2 octane points compared to the east coast anyway.

Get gas from $afeway, I get about 120 miles from a tank...get gas from anyplace else and I get more like 140 miles from the tank...thats some 15-20% difference if my math is correct.

I'd guess something is not running right with your bike if you're getting 60-ish miles per tank. either not all cylinders are running, or something else. When you throttle up do the RPM consistently increase? Its possible you're not running right and the more throttle you give the richer the mix.

Switch to regular gas....check that all 4 pipes are getting hot when you're running, run a tank of fuel system cleaner thru, make sure you're not driving around on full choke all the time too, that will suck up gas as well I believe....

**BassCliff** · 08-14-2007, 02:06 PM

It's a gas!

Originally posted by Steve

The quickest and easiest way to better fuel efficiency is to use the proper fuel. Dump the "premium" and use "regular" gas.

It is not called "premium" because it's better. It's called "premium" because it has higher octane. Octane does not contain power. Octane resists detonation caused by compression temperatures. By design, "premium" is harder to light (that's why it resists detonation) and burns slower (that's why you have to advance the spark). In a standard engine (like most of our bikes), it will not finish burning completely before the piston is going down too fast for the burn to help. You lose a lot of power there.

Mr. Steve,

This is very interesting. I've been using premium in my 850 and getting 36-38mpg, wondering why I wasn't getting 40mpg or better like other 850 riders. I'll start using regular gas and see if the mileage improves. Thanks for sharing your insight.

Thank you for your indulgence,

BassCliff

**sonicgroove** · 08-14-2007, 03:15 PM

Sorry, I didn't mean this as a thread jack, I figured since his post is similar to mine I should post in the same thread rather than create a new one so it could possibly be stickied for future references. I'll copy and pasted my question in a new thread along with pics of the bike. 83 GS550L.

-groovin

Poor mileage on my '82 GS650G

Poor mileage on my '82 GS650G

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