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Gravity/automatic fuel cutoff

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I put a SmartCarb on my KTM, and I love it.  But, there's no overflow on the carb, just a manual drain valve.  I'm guessing this is because the float bowl is pressurized when the bike is running.  I tipped the bike over last weekend (log jumped out at me) and pinned my leg under the bike, so it took a bit to get my leg free and get the bike upright again.  During this time, the float valve was obviously open and it way overfilled the carb with fuel.  When it wouldn't start again, I noticed fuel up in the pressurization tubes on the side of the carb, so I shut off the fuel, drained the carb, and then kicked it over with the throttle wide open to clear it out.  It started again pretty quickly, but it was still a PITA.  Luckily the fuel was high enough to where I could see it overfilled, otherwise I would have been there for a LOT longer.

Does anyone make some sort of gravity cutoff that I can put in the tank or fuel line that would prevent fuel from flowing when the bike is not in it's intended operating position?  :)

Now that I know, I can manually hit the fuel shutoff right away if I can get to it.  But, it would be nice to have something.

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11 minutes ago, William1 said:

The Smart Card supposedly already has a check valve. One of the big selling points is when the bike tips over, it is not supposed to flood.

Interesting, you are correct.  I called the SmartCarb guys and verified this.  They said it might have just been at an angle where the ball didn't completely seat properly.   I have tipped it over before and haven't had a problem, but it wasn't down as long as it was this time.

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I spent hours studying this system. Hooked up a mock tank and turned the carb every way possible. It has 2 check valves. The first one to flood will close off usually, but the second,  higher one, unless right side up, does not want to seat and seal. And, even if it would close as designed, the bowl is overfull at this point. Imagine a pipe with a ball in it. Compound angles will not seat. Shutting off the fuel will slow it down, but it will still drain into your intake because the system is still vented, through your air filter. But at what I think is about 50% less. Once the bowl gets full of fuel, then it will pour fuel. The ball seats will sometimes work, if the angle is ideal to the seat. But that's rare. Best thing to do is to leave it running on it's side. It will not hurt it if it's a 2T. Not sure about a 4T with the oil breather location. I told SC that they should do a gravity ball check valve for a bowl drain. They were not interested in my solution to a problem they don't acknowledge. And it's not a problem for 98% of their customers. Very rarely do riders ghost their bike up a ledge, slide down 50 feet and the bike is on it's side for 5 minutes as you climb up to it. This is why I say 98%. Truth is, all carbs can drain into the intake when left on there side if the bowl drain is blocked with dirt.  The bowl drain overflow is designed to keep the bowl from filling up, then bleeding through/past the metering rod/needle, filling the intake, possible hydrolock if left long enough. I think it's a great carb. I just think that it needs clarification.  Hmmm, thinking about this,  If you look at the advertising, I don't think they misrepresent the carb. We, the consumer, read to much into "internally vented". I think we assume this means it will not drain into the intake. And, the manual gives instruction how to clear this out if it does happen, a warning to watch for, if I recall. So, for me, I just think that someone should point this out, just so we know. Before I purchased the carb, I noted I was excited about a carb that I could just lay on it's side and not worry about it. And no one on the forum corrected me. But, to be clear.... I like the SC. Good company, great product. Worth every penny. Just know that it can flood the engine if the ball seats are not at optimal angles relative to the check valve. It needs about the same done for it as we typically do for a conventional carb. We typically shut the fuel off and or stand the bike up. Just treat the SC the same and it will be loved

Edited by 1gr8bldr

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