poor gas mileage/ running rich

[Malpert]

hey there,
i've got a 1982 GS1100L i just bought about a couple months ago. Shes running really rich and getting poor gas mileage, about 70 miles a tank! I just changed the plugs and they were carbon fouled. The two on the left hand side of the engine had white on the insulator. What does that mean? Is this an obvious carb job or could it be something more? Another obvious question would be am I running the right type of fuel in the bike (I fill it with premium). Any help would be appreciated.
Thanks,
Matt

[oldschoolorange]

The white plugs indicate a lean condition, check into your carbs and look for vacume leaks

[nabrams]

There are many reasons why you might be getting bad mileage (especially for a bike that's been sitting for a while).
See other posts, but here are some things to check:
1. Restriction in the airbox/filter
2. Poor compression (for those cylinders that are fouling)
3. Stuck or leaking floats and/or float needle valves (for the carbs of the problematic clyinders).
4. Improperly firing coils or ignitors (note: though you may see spark, coil performance degenerates at high RPM, especially for old worn-out coils - see Wikipedia).

The fact that you'r getting some lean plugs and some overly rich plugs points to the carbs as the most likely culprit.

[Steve]

hey there,
i've got a 1982 GS1100L i just bought about a couple months ago. Shes running really rich and getting poor gas mileage, about 70 miles a tank!

Since that is about half of what you should expect, I am glad that you recognize there is a problem.

I just changed the plugs and they were carbon fouled. The two on the left hand side of the engine had white on the insulator. What does that mean?

Conflicting pictures here. At first, it sounded like all the plugs were carbon fouled, then you say that two had white on the insulator. Carbon fouling happens in a very rich mixture. White is due to a lean mixture. Sounds like you have multiple problems here.

Is this an obvious carb job or could it be something more?

The problem is most likely in the carbs, but you can not automatically rule out ignition, either.

Another obvious question would be am I running the right type of fuel in the bike (I fill it with premium).

NO. Unless you have a big-bore kit, hotter cams, etc., you don't need premium fuel. You do NOT get more power just by using premium. In a stock engine, you are more likely to foul the plugs and the valves by using premium fuel. It is not called "premium" because it is better fuel. It has a higher octane rating. Octane does not produce power. It is a measure of resistance to self-ignition. Higher-performance engines have more compression, which raises the temperature of the fuel mixture. It is possible, in some cases, to raise the temperature enough that it will ignite before the spark lights it. This is the 'knocking' or 'pinging' that you might hear. A higher octane rating makes the mixture harder to light, so it waits for the spark to light it. The higher heat from compression will help it once the spark sets it off. In a stock engine, there is not enough heat from compression to help finish the job, so you are left with unburnt deposits.

For your particular problem(s), start with another set of new plugs, make sure they are the proper plug, not just a replacement for what came out. "Previous owners" are notorious for putting in whatever they feel is best, not necessarily what is right. NGK B8ES plugs are what is recommended. Examine the "choke" plungers on the top left sides of the carb bodies. When you move the choke lever to the OFF position, do they all go in all the way? Push on them, especially #3 & #4 to make sure. If that does not do anything, you will have to remove the carbs, to a thorough cleaning, and make sure all the jets are the proper sizes. Since you have them all apart, it would also make sense to replace all the o-rings (available from cycleorings.com). Also check the condition of your intake tubes. These are the rubber tubes between the carbs and the head. They should be soft and pliable. There are o-rings between the tubes and the head that are notorius for giving problems, so replace them, too. Replacing all the o-rings does not involve much cash. If you need to rplace the tubes, however, they are about $20 each.


.

[swrupert83]

Just to throw it in there.... premium fuel is actually LESS combustible then low grade... the rating is based on the anti knock and protection properties of the fuel....

[bonanzadave]

hey there,
i've got a 1982 GS1100L i just bought about a couple months ago. Shes running really rich and getting poor gas mileage, about 70 miles a tank! I just changed the plugs and they were carbon fouled. The two on the left hand side of the engine had white on the insulator. What does that mean? Is this an obvious carb job or could it be something more? Another obvious question would be am I running the right type of fuel in the bike (I fill it with premium). Any help would be appreciated.
Thanks,
Matt

Ive been waiting for someone to bring this up again. I set my trip gauge to zero last week and now I just put in 4 gallons. The grand total on the trip gauge is.............99 miles. That really sux. I use premium because all my other choices are ethanol blends. The co-op has non oxygenated premium for anything that has no catalytic converter. Boats, MCs, lawn mowers, etc...
I thought ol bessy was running pretty good. Fires right up. Pulls like a freight train. Just really sh!tty mileage.

[Motor Hack]

Me Toooooo

I have an '83 GS850GL that get about 85 miles/tank. I think I might that I might have some leaking valve stem seals. What kind of impact might this have?

[chef1366]

It will just eventually foul the plugs.
Pull the carbs and clean them. Make sure to change the o-ring behind the intake boots. When done the airbox needs to be sealed with a good seal on the carbs.