Awful Gas Mileage

[sebring38]

Just read with interests the thread on How Many Miles Per Gallon? and noted most are getting 40's to 50's. As for my 82 GS850G I am getting about 23 mpg.
Bike runs very well, starts and idles nicely, seems to lack a little at low and mid rpms, but really cooks at 6,000 and higher.
I do occasionally notice a slight gas smell, but not always. I have looked it over and do not see any gas leaks.
Valves have been readjusted within last 1000 miles, but even before the valve adjust I was getting this lousy gas mileage.
Any comments would be appreciated.

[lord1234]

are you running PODS or a non-stock pipe? you're jetting might be off...

[rustybronco]

i have a gs850gz stock 46-47.6 mpg
please list as much details as you can, how long have you owned it ect.

[Jethro]

Poor gas mileage is a tough one to diagnose. It basically could be ANYTHING. But your mileage is really bad. I would take some plug reads and see what they say.

[flyingace]

It depends to some extent on your riding style. I'm very conservative and I get low to mid 40s. High 30s around town. I agree low 20s is too low even if you are always WOT.

Some that have replaced stock air intake and exhaust have reported poor mileage at highway speeds. I guess the extra jetting required just sucks more gas. However, they measure rich or lean based on plug reads which I don't think is all that acurate. They work hard to get the plugs 'tan' and not 'white' - but plugs in stock machines are white. Mine are all white and the bike runs great. But I'm probably a minority of one with that opinion.

[rustybronco]

but plugs in stock machines are white. Mine are all white and the bike runs great. But I'm probably a minority of one with that opinion.

mine are white except for the very tip and the tip of the side electrode and NO bog or hesitation all the way up to red line except when its hot out and i take off at a very low rpm after stopping from highway speeds at a light, and then its a very little blurble at 900-1300rpm.
so i guess your not the only one...

[flyingace]

I think sometimes symptoms associated with reduced vacuum to the CV carbs are interpreted as running lean. The assumption is that surging and inconsistent idle are a result of lean carburetion - but I've seen no actual proof that this is the case (since I don't believe white plugs are proof). If I was rejetting for pods/exhaust, I would forget about the plugs and push the lean limit until it started to ping, than back off.

I know this is heresy. but I can't think of another reason why bikes get crappy mileage after rejetting for pods.

[sebring38]

are you running PODS or a non-stock pipe? you're jetting might be off...

No, I am running stock air filter and pipe/exhaust. I have made sure airbox is tight. Carbs were rebuilt by suzuki shop and new jets put in (wonder if they are bigger than stocke??) also valves adjusted. To me it seems to not be getting enough air. But, I have new set of PODS and am tempted to put them on and just see what happens. If it is not getting enough air, the pods should fix that. What do you think about that idea? By the way, thanks for all of the replies.

[flyingace]

One thing your plugs will tell you is if you are running rich. They will be black and sooty looking. Check them first.

There is no reason your bike should run rich with stock airbox and exhaust. Most GSers agree that the CV carbs on your bike run best with stock equipment. Don't change to pods until you've sorted out the problem.

[rustybronco]

No, I am running stock air filter and pipe/exhaust. I have made sure airbox is tight. Carbs were rebuilt by suzuki shop and new jets put in (wonder if they are bigger than stock??)

just because a suzuki dealer o/hauled them dont make it right. do plug chops and do plug reads.
check timing and advance also.

[NickNoo]

Plug readings are essential if you want the engine to perform at its best.
However, you need to be sure that your carbs have the correct jets and are balanced, otherwise the readings wont be of much use.
The CV carbs on the GT were factory-set to run lean due to tight emission controls at that time and the mixture screw was sealed to prevent tampering. As we know, its easy to remove the tin caps and play around with the mixture settings (turn the screw anticlockwise to richen the mixture).
I have found it best to richen up the mixture a little so that the ceramic part of the plug is "tan" in colour rather than "white". The engine definitely runs a bit cooler and is smooth and responsive at any rpm. If I run it lean, I get a slight flat spot at around 3000 to 3500rpm and a little backfiring on the over-run. I am no mechanical expert, but I would guess that engine life may be longer if it runs a little on the rich side.
Incidently - I found that setting the mixture screws to the highest rpm results in a very lean setting (I wouldnt rely on this method alone - plug readings are better IMHO).
I have found that these mixture screws are VERY sensitive - half a turn makes a BIG difference to the plug reading.
I get around 55 to 65mpg from my 850GT (UK mpg) - thats about 47 to 55mpg (US).

Heres a good reference for plug readings :

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

Stock jet sizes from the Haynes manual for the GT850 :
Main jet - 115
Main air jet - 1.7
Jet needle - 5D50
Needle jet - X-5
Pilot jet - 40
Pilot air jet - 190