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Discussion Starter #1
So I got a replacement petcock for the twin. But it only has one outlet, the old one had two, one line for each carb coming directly out of the petcock.

So I got a "T" and hooked it up. but no matter how I hook it up, it always seems as though one tube is full of gas, the other seems to be starving for gas, never fills up, but I can see gas running into it. Is there a weird vacuum/pressure thing going on here that I dont get?

So I put the old petcock back in, and basically the same thing happens.

Now don't get started on float levels, I've done all that, and besides, if I drain the tank, and start all over again, it will happen on the OTHER side. weird.

Helmholtz Kneuter valve?
 

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plugged breather on a carb? cap might not be breathing properly either.

just shootin ideas????????

latered
 

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Discussion Starter #3
not plugged breather. I took both carbs apart, and fuel flows through BOTH breathers when I tip them on their sides.
 

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thats why i stayed away from running one outlet on my new petcock. its a dual outlet deal. it was either that or 2 seperate petcocks.




jc


aaron, send my wheel.
 

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My vote is for trapped air. Usually not actually a problem as fuel will get by it anyway, but if it bothers you try removing the airy side from the carb, loop it up (but lower than the tank) and open the petcock. when you've got a good bit of fuel squirting out replug into the carb. Poor man's gas bleed.

Oh, and I recommend smoking while you do it.

A
 

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Discussion Starter #6
That sounds like an interesting idea . . . . I figured it was trapped air, but how to get rid of it. baker suggested it was like an indoor plumbing job, running a T off a 1/2 in copper, you have to have a piece of pipe that runs high to bleed off air off of the one side . . . .
 

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What Xander said....happens all the time to my bike...looks like no fuel is flowing but it really is. I've never had it cause fuel to stop flowing to the carb if the carb needs it.

Sometimes both lines are full of fuel, sometimes, one, sometimes neither...carbs still seem to get the fuel they need. Often after a race I'll notice they are both full of fuel.
JohnnyB
 

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something similar happens when draining a tank with 2 fuel lines. You have both routed into the gas can but fuel usually only flows out of 1 most of the time. I figured the pressuure must equalize itself after a while when it's feeding the carbs as they are equally full when I look inside.
 

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my boneeville has a neat little copper crossover. its literally 2 pieces of 5/16" tube coped together adn soldered in the middle. so they share both petcocks. and the little thing formas and "X" shape and just hangs under the tank.


jc


aaron, send my wheel.
 

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i don't get it. should be no problem...have you run the bike and found fuel starvation problems. just as basement mechanics (winter) misses problems, sometimes nonexistent problems arise...a little too much time looking at something can sometimes be a big problem. huh?
parks
 

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Discussion Starter #11
no, there is no fuel starvation, necessarily, it just looks weird. Everything in my life has to be aboslutely symmetric or something is wrong with the kneuter valve.
 
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