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Discussion Starter #1
Just like the title says, my S40 stalls when I'm on the highway, usually after 1 or 2 miles, or even going fast (~55 mph) in 4th, as I found out today. Throughout town, she purrs like a cat, but I can't figure out the stalling. The only thing I've done to alleviate this is run some Seafoam in the tank. But it still stalls. Any ideas?
 

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Sounds like restricted fuel flow.

Check the tank vent and fuel filter and look at the gas lines for kinking.

Does that model have a manual petcock or does it have a fuel pump ??

P.S. Seafoam is NOT a really good cleaner; it's mediocre at best......and WAY overpriced.
 

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Discussion Starter #3
Sounds like restricted fuel flow.

Check the tank vent and fuel filter and look at the gas lines for kinking.

Does that model have a manual petcock or does it have a fuel pump ??

P.S. Seafoam is NOT a really good cleaner; it's mediocre at best......and WAY overpriced.
Petcock. According to my Clymer manual, it's equipped with a "small fuel filter screen in the fuel shutoff valve." But my fuel doesn't have that option--only ON, RES, PRIME. No off. So that screen might be clogged, but I wonder how to get to it without taking the tank off. Also, I can't find where the tank vent is at.

What do you recommend instead of Seafoam?
 

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With that vintage of petcock, ON is automatically OFF without any engine vacuum to open the tiny valve inside.

PRIME is never OFF. Try running it on RRIME for a bit.
If that works, the vacuum valve in the petcock may have failed......or the vacuum hose feeding it might be leaking.

That screen really doesn't qualify as a fuel filter. Once you get the present problem fixed, installing a small inline filter would be a good idea.

The tank vent should be IN the gas cap. When it stops running, gently open the gas cap. If you hear a little "whoosh" and then it starts up again, the vent is stuck or plugged.

Gumout or Berrymans B12 are MUCH better cleaners.
Seafoam was originally designed as a marine fuel stabilizer.
 

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Easy Rider has a point. I have a C50T and that fuel line tends to get bent if the tank is moved or removed and put back on.
 

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Discussion Starter #6
Yep it does look like a kink in the gas line, thanks easy rider and for the confirmation password. It almost looks too short but I wiggled it a little an it looks a little bit better. Wonder if I should get a longer tube and where I would get it.

On a side note while I was looking at this whole shebang I noticed another identical tube going from my carb and ending nowhere. Should I have this just floatin without being plugged in anywhere? Couldn't figure that one out, will keep lookin at the Clymer.
 

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You can get new gas line hose at any auto parts store.

It is not unusual to have a vent or overflow hose with nothing connected to it.
While the bike is running, put your finger over the end of the open hose to see if there is any vacuum there.
If not, it should be OK.
 

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Discussion Starter #8
Well I took it out on the freeway today but it started stalling around a big semi after only half mile or so. Turn the petcock to Prime however, and wouldn't you know it, it smoothed out and started running fine again on Prime. So what does that mean, bad petcock?
 

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Probably not working from vacuum...the diapragm responsible for this may be holed...that or the vacuum supply line is kinked or similar. If the fuel line had a kink in it then there is a high possiblilty the vacuum line does too.
 

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Yes.....the vacuum operated mechanism in the petcock isn't working....either because it has gone bad or the vacuum line is off or leaking badly.
Also possible that the "normal" fuel pickup is plugged up but that is highly unlikely.
 
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