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This bike has been an on and off pain. It starts up just fine and idles just fine, though it does need to idle high (4-5k rpm) for warming up, but it's old and I expect that. When I take it out on the road, it'll ride fine for a bit, but then it seems to bog down when I roll on the throttle at all. Then it slowly dies out and in order to keep it running, I have to open up the choke which takes it up to ~5k and that doesn't seem healthy. What on Earth would be causing this issue? I'm guessing carb problems, but I am no motorcycle mechanic.
 

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Female Rider
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When this happens open your gas cap just to see if it is possibly a clogged air vent. I really hope it is something that simple. Also you could pull the fuel line to make sure it is going through. If the bike sat for a while the gas could have gone bad and clogged something up. I'm a firm believer in trying the simple things first. Good Luck.
 

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Hate to be a broken record here, but a faulty petcock can cause your issue.

If your petcock has a prime position, and it is defective, it will always be priming the engine by allowing gas to flow directly into the carb without entering the bowl. This can also cause overflow issues when the bike is off.

The prime is making the fuel rich when it shouldn't...and then you twist the throttle and make it even richer...and the bike...bogs...bingo.

High idle "no matter what you do" is a sure sign of a bad petcock.

Old petcocks use a vacuum mechanism to shut off fuel flow when the bike is off. That same vacuum port also acts as the prime...if the mechanism is messed up, you will prime the engine all the time...and if it's really messed up, gas will leak out of the carbs.

Turn the gas to on.

Run the bike.

Shut off the bike but leave the gas on.

Pull the vacuum hose off the carb...there should be no gas in the hose.

You can also put the hose in a container and see if it leaks slowly over time...but given your description of the problem, I'm betting it's leaking all the time and heavy.
 

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Greatest Member Ever
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Really?? I leave for a short time and there are noobs making unfounded diagnosis' ? Wade is correct. The problem lies in the slow jets being gummed up. A properly running GS (at any cc) would idle approx at 1000rpm, (perhaps 3500 with the choke applied). Although a defective petcock COULD cause trouble if it allowed constant fuel flow, the float valve needles should curtail that issue. What the OP is describing is not a floaded carb, it is a fuel starved condition.

First, check what Moni said... make sure fuel can move from the petcock properly. If the petcock works as it is ddesigned to do, and the bike runs as long as the choke is on, then you have to clean the carbs. The slow jets are choked up.

Fact is, you haven't responded to this thread in quite a while... I fear I just wasted my time....
 

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That stuff about the petcock and always priming the engine doesn't sound right. The stock style petcock has "Pri", "Run", and "Res". Usually we leave the bikes with the valve switched to the Run position. The fuel pickup has a pressure actuated device that only sends flow when asked for by the engine. You can leave the valve set to Run, pull all the hoses and remove the tank and nothing should drip. If the petcock valve was set to Pri, it would bypass the pressure actuated pickup and send fuel to the carb. The carb only has one fuel inlet so gas still goes into the float bowl, and a properly working float would shut off the flow when full. When the float rises, it closes a needle valve to the fuel inlet.

Since the OP hasn't responded in a while I won't get into much else, however it would be good to know if the carb or exhaust was ever modified. An high flow/performance/baffle-less exhaust without rejetting the carbs could cause a similar kind of issue.

One thing I remember about my 650 is that, after owning it and riding a few thousand miles, it seemed to like a squirt of dry gas every now and then. It was my first bike and I had no idea about the condition of the carbs so the dry gas was probably a band-aid fix, but I do know that burning ethanol results in increased water in the fuel system, and fuel with extra water will burn lean.
 
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