Quick Carb Jet Questions

[hookemdevils22]

Hey all, I picked up an 82 GS650 shafty a few months ago. I’ve noticed that it has a flat spot in the midrange between ~4-6k rpm when I get on it. Bike idles fine, though there’s the smallest hint of off-idle stumble, and gets 39mpg on mostly 45 mph city roads. PO put cheap pods on, otherwise the bike is stock. I pulled the carbs and noticed that it has 125 main jets vs. 110 stock per the sticky. It still has the 5C45 non-adjustable needle, although I did remove the small metal washer underneath, effectively pushing it down further in the jet and hopefully leaning it out a touch.

Should I look at a smaller jet, maybe pickup 4 of each 115 - 122.5? And what can I do about the lack of adjustment in the needle? I saw the Dynojet kit, but the jet numbers don’t align (they have a 155 for pods only and 160 for pods + exhaust). I’ve read the general jet size guide but want to verify before pulling the trigger on anything.

I’ll be asking about exhaust mods down the road but want to get her running right first.

eta photos of the bike
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[Nessism]

To lift the needle, you need to reduce the thickness of the plastic washer on TOP of the clip. That's because the spring under the needle pushes the needle up, until it contacts the plastic hold-down plug thingie. Removing the washer as you did, does nothing.

Some guys shave down the plastic spacer over the clip, and other guys find some tiny washers, and stack them to some height less than the original plastic spacer thickness.

Regarding main jets, it's common to jump 3 steps when running pods. Or better yet, get a Dynojet kit. And make sure you have proper pods, not the junk china cheepies. K&N, APE, UNI, something quality, are the way to go.

[chuck hahn]

what do the plugs look like

[Nessism]

what do the plugs look like

If using plug color to judge jetting, plug chops are necessary. Just looking at the plugs overall, doesn't help much.

[pdqford]

I thought the original poster was trying to lean out the midrange fuel.
Maybe I missed something?

[hookemdevils22]

Plugs don’t look too bad, but then I haven’t isolated them (check at idle, check at midrange, check at WOT). I might give the additional washers above the clip a try to lower the needle and lean it out. Otherwise I have no issue with the DJ kit, as it would allow more adjustment.

[93Bandit]

Are you attached to the pods? Maybe put a factory airbox back on and use factory jets.

[Suzukian]

Leaning the bike out when you put on pods is going in the wrong direction, as far as I've always done, and do.

[pdqford]

Except that he is already five sizes over stock.
If he leans out the middle and it gets worse he knows to go bigger on the mains.
If it gets better and it gets better, he knows he is already to big.

[Suzukian]

Except that he is already five sizes over stock.
If he leans out the middle and it gets worse he knows to go bigger on the mains.
If it gets better and it gets better, he knows he is already to big.

Thank You for clarifying that me.

[hookemdevils22]

I went ahead and pulled the trigger on the DJ kit since the OE needles aren’t easily tunable. I just wish I understood how DJ jet sizes (kit comes with 155 and 160) compare to stock (110). Thanks all for your input.

[Suzukian]

Nice looking bike, is that the stock paint? Looks really good.

[hookemdevils22]

It’s a respray, a solid 20-footer. I do like the color. The guy I bought it from had the seat redone and quick-sprayed it. I’ve replaced gauges (with those from a 81), done brakes, cleaned up wiring, upgraded R/R to Compufire, replaced lighting and removed the rear splash guard. I’ll need tires before too long, and I’m considering exhaust if anyone has recommendations.

Got the DJ kit installed, but the fuel line was hard as a rock and cracked, plus it’s crazy hot so I haven’t been able to test ride.


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