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Stock jet sizes for a 83 GS750ES

  • Thread starter Thread starter Anonymous
  • Start date Start date
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Anonymous

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I bought the 84 GS750ES with individual cone air filters. Its not running rite so I was thinking of finding a stock airbox for it. But I want to know if the previous owner rejeted. If thats the case it would be better to just buy a jet kit and tune it the way it is.
Does anyone know the stock pilot, main, and air jet sizes, so I can see if mine are different?

Also does anyone know if there is factory manual online somewhere. Or a carb tuning resource.
 
If he rejetted you'll have adjustable needles on the slides. Stock mains are 117.5, main air jet is 1.7mm, jet needle 5D12, needle jet Y-6, pilot jet 37.5. The only thing that would have been changed jetting wise is the needles and the mains. The slides would have been drilled and new springs on the slides for better throttle response. The caps would have been removed from the pilot screws.
 
Main jet = 117.5
Main air jet = 1.7
Jet needle = 5D12
Needle jet = Y-6
Pilot jet = 37.5
Starter jet = #45

Float height = 22.4 +/- 1.0

Hope this helps.
 
My air jet has 790 on it do I have to mesure it to know the size. I also had the needle and slide out, how do you know if its adjustable or not. And what and where is the starter jet. Sorry but I'm new to working with motorcycles.
 
Air jets aren't anything you would be replacing for normal tuning purposes so don't worry about the designation. They are almost certainly stock.
 
Geuss I'll have to take a look at the jets when I have some time I'll let you know what I turn up.

I went for a ride just now and I was paying atention to the revs and the flat spots the major flat spot is at 2000-3000 rpm no more noticable flat spots but at 7000 rpm it pulls significantly harder. I pulled out the plugs and they had sort of an off white color. How dark should the plugs be?
 
It's normal for the '83 and up 700/750 models to pull harder in the upper revs. It's just they way they are tuned. Your flat spot is right about where you are coming off the pilots and onto the needles. You probably need a little fine tuning of the screws and maybe raise the needles a notch if they are the adjustable aftermarket type. Try fiddling with the screws first though. Adjust each one for the highest, smoothest idle.
 
I raised the needle a notch and the midrange is more responsive and powerfull. My adjustment screws are already out 3 and 3/4 so I was thinking of getting a pilot jet one size bigger then go from there.

Another thing, when I choke the engine it gets all the way up to 4000rpm and the engine won't idle with no choke until it has warmed up for about 5 min. When its warm it idles at 1500 rpm. Can you speculate on whats going on.

I have a feeling this is related to that dead spot.

Thanks for all the help so far.
 
If you're that far out on the screws then you're off the jet and just wide open. You may need a carb cleaning to get that circuit operating better. You could try just running a good injector cleaner like Chevron Techroline for a couple of tanks and see if you can fine tune them downward. If you use a spray type cleaner to clean the circuit pull the screws all the way out and remove the tiny o-rings from them. The spray type cleaners will ruin o-rings. Those o-rings could also be suspect if they are shot.
 
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