I have a 2009 Suzuki GS500, about a year ago I wanted to mess with it a little to get a little extra power out of it (big mistake). I never got it to run right so I gave up and put everything back to stock (besides the exhaust) but to my surprise it still wouldn't run right.

It starts, idles, and accelerates fine, but at 6-7k rpm, I lose all power and the bike stalls. If I let go of the throttle it will catch itself before dying and will continue idling like nothing ever happened. When riding it, this issue will happen sooner around 3-4k rpm. I've cleaned the carb like a million times, tried different jets and needle heights (because of the exhaust) and nothing has made any change. Also I've messed with the float heights adjusting them both ways and still no change.

It's not clogged/starving for fuel. I don't believe it's an ignition problem because it runs pretty much perfect if I put my hand over the intake. I can't find any vacuum leaks, spraying brake cleaner around the hoses and fittings doesn't change anything. I desperately need some help, I feel like I've looked over every part of the bike multiple times and can't find anything wrong and can't find anything that makes it better.

Any suggestions or answers would be greatly appreciated, feel free to ask questions.

What about your intake system, is it a stock air box w/stock filter?

Sounds like the slides are not coming up. Can be many reasons why. Sprayingb rake cleaner? Seriously? Inspect the diaphragms and make sure they are intact, no pinholes or tears. Then fix the vacuum leaks the right way.

Any chance you got the choke jet and main jet mixed up?

Dont do rando crap like spraying something somewhere and hope it miraculously fixes something.
And jetting and carburetion is related to throttle position, not rpm. So at what throttle position does it stall ?
But Mr72 is likely close with the assesment that slides not coming up.
BTW yes on his 2nd point too - mid mains and mains while they will fit into each others spot, should not be cross fitted, they are vastly different orifice diameter.
Cool.
Buddha.

yeah if the jets are mixed up then regardless of slide position not enough fuel will come in once you are above the rpm/throttle range where you are running on pilot.

Brake cleaner, carb cleaner, etc. are all solvents that can damage or destroy rubber parts such as o-rings and the diaphragms. If you have a vacuum leak then it will suck the solvent right in to the vacuum chamber and deposit it right on the diaphragm, making your problem far worse.

Thank you for the replys. Sorry for the confusion, but I wasn't spraying brake cleaner hoping it would fix it. I was really just saying I've checked for vacuum leaks, both by inspecting for cracks and by spraying brake clean around the common areas to see if it affects the rpms.

I currently have the stock airbox and filter, but had the same issue with a k&n lunchbox with larger jets. The exhaust is somewhat similar to stock, definitely not just straight piped. I do have a baffle with fiberglass, I've asked around on Reddit and somebody said that is a no no and likely my problem. Later this week I will take that out and see if there's a change. Any opinions on that?

The problem happens somewhere around half throttle, sorry I'm not exactly sure at what point, but it's always in between 6k and 7k rpm. Happens the same whether I snap the throttle fully open or slowly increase it.

Lastly I believe I have the jets all in the right locations, just to be sure though, the mid main is the one that interacts with the needle, correct? The main is the one that does not and sits higher up in the bowl, correct? If I have that backwards then that would be very unfortunate and a huge loss of troubleshooting time lol.

Thank you again for all of the replys and help.

Quote from: I Am Fatboi on March 07, 2022, 12:17:05 PM
Thank you for the replys. Sorry for the confusion, but I wasn't spraying brake cleaner hoping it would fix it. I was really just saying I've checked for vacuum leaks, both by inspecting for cracks and by spraying brake clean around the common areas to see if it affects the rpms.

Yeah, that's what we were responding to. DO NOT SPRAY STUFF ON THE CARB TO FIND VACUUM LEAKS. If you MUST use this technique, use water.

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I do have a baffle with fiberglass, I've asked around on Reddit and somebody said that is a no no and likely my problem. Later this week I will take that out and see if there's a change. Any opinions on that?

It won't help. That's my opinion.

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The problem happens somewhere around half throttle, sorry I'm not exactly sure at what point, but it's always in between 6k and 7k rpm. Happens the same whether I snap the throttle fully open or slowly increase it.

Yeah that's where you transition onto the main jet.

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Lastly I believe I have the jets all in the right locations, just to be sure though, the mid main is the one that interacts with the needle, correct? The main is the one that does not and sits higher up in the bowl, correct?

I'll let Buddha or someone else who is more familiar with these later carbs answer for sure, but I believe you have these jets mixed up. The main needle definitely goes into the main jet.

FWIW you probably should also check the diaphragms since you sprayed brake cleaner on them.

Mid mains does not have needle sticking in it. The needle sticks into the emulsion tube, and main - the real mains goes in the bottom of emulsion tube. PS: (Mr72 is right and succint)
You have pinpointed your problem. The mains - with a large diameter orifice - 130 or higher (1.3mm) is the one with the needle, and sits lowest in the carb as it is in the bike.
The mids with a size of 60 (.6mm orifice) sits higher in the carb and needle does not go through it.

So swap the jets so lowest in the carb as assembled onto the bike has some large number - 130-150 and needle goes through it. Test and post back.
Remember, do 1 change at a time, observe the changes and determine if you had a positive effect or negative effect.
Cool.
Buddha.