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Carb problem 78 GS1000E

  • Thread starter Thread starter Anonymous
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Anonymous

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I,m restoring a 78 GS1000E, got it on the road this past week and seem to have a carb problem. First off it seems to run ok but drinks alot of gas my millage is 20-25 miles per gallon, maybe less. Also there is a adjustment in the float area that all Suzuki says about it is DO NOT ADJUST THIS SCREW it is factory set and will mess up your carbs if you screw with it, well someone did and I think thats part of my problem. The idle is really unstable, it fluctuates alot and after I adjust it it does not stay in adjustment or stable. I can adjust the air/fuel screws on the outside of the carbs and get it running pretty good but its not quite there. What is this screw adjustment inside the carb for, everything else has been well cleaned. Also it seems like you have to give it alot of throttle to get it going and when you let off the throttle it slows really fast.
 
Re: Carb problem 78 GS1000E

Been there, done that, had that problem on two bikes of that year and model that I worked on recently.

The screw under the carb located at the front of the floatbowl is the pilot fuel screw. Assuming you have stock airbox with lid and clean filter, stock exhaust, set that screw to 1 1/2 turns out. Set the airscrew (the screw on the side of the carb above the bowl gasket surface) to 2 turns out.
You need to synch the carb vacuums. I can pretty well guarantee your synchronization is deplorable if your milage is that bad. :-) Set the 2 and 3 carbs vacuum level about 1 in hg (2.5 cm) less than the level on the 1 and 4 carbs.

If you have a strobe timing light, check your advance to see that it is on the |F4 on the 1,4 side and the |F3 on the 2,3 side. Those are your 32btdc advance marks. Adjusting carbs is not going to help if your timing is off.
Full advance occurs at aprox 3500 rpm.

Earl




Jeff Kalin said:
I,m restoring a 78 GS1000E, got it on the road this past week and seem to have a carb problem. First off it seems to run ok but drinks alot of gas my millage is 20-25 miles per gallon, maybe less. Also there is a adjustment in the float area that all Suzuki says about it is DO NOT ADJUST THIS SCREW it is factory set and will mess up your carbs if you screw with it, well someone did and I think thats part of my problem. The idle is really unstable, it fluctuates alot and after I adjust it it does not stay in adjustment or stable. I can adjust the air/fuel screws on the outside of the carbs and get it running pretty good but its not quite there. What is this screw adjustment inside the carb for, everything else has been well cleaned. Also it seems like you have to give it alot of throttle to get it going and when you let off the throttle it slows really fast.
Click to expand...
 
Hi. I have a '79 GS1000E. Earls advice is good. Allow me to add.
The pilot screws (underneath) are sharp tipped, so if you seat them, do it lightly. These are for fine tuning the pilot circuit. Because of small differences in each cylinder, they are commonly set differently from each other. Generally, on a stock bike, they will be anywhere from 1/2 turn to 1 1/4 turns out. They are very sensitive and it can take a while to adjust them to get the plugs burning like they should.
The side air screws should always be adjusted to achieve the highest rpm's possible. Put the bike on the centerstand and warm it up first. Adjust each screw until you hear the rpm's max out. Do this to all four screws and then re-set the idle to 1,100 rpm's with the idle adjuster knob. Both these screws can be very tight, so use a GOOD fitting tool and be careful of stripping the heads.
This may stop your problem, but to do a complete job, a good carb synch is important. As Earl said, the ignition timing must be set first, also the valve clearances should be good before a carb synch.
If you have an idle that is rising too much as the engine warms up, you probably need new manifold o-rings. Check the condition of the manifolds too. Apply some hi-temp' bearing grease to the o-rings and torque to 6 ft/lb.
There are many things that can cause your problem. Don't hesitate to ask if you need to take the carbs apart, etc. There isn't anything about these carbs or ignition that Earl and I can't answer. :)
 
I would also encourage you to change your float valves and check your float heights. Sticking float valves will dump raw fuel, either into the overflow tube or into the engine.
 
Had similiar carb issues with my '79 GS1000 and followed Keith and Earl's advice. Now it runs great, just be patient. As one adjustment can usually affect another, it could take repeating the carb tuning steps a couple of times to get it perfect.
 
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