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GWGAllisfan

Carb question (Maybe fixed?)

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GWGAllisfan
Can someone tell me what the difference is between a Flo jet carb meant for a fuel pump engine and one meant for gravity flow? I know they have different seat kits, but is that something I could see by looking at it? Is there any way to know for sure which you have if you bought one of unknown origin? My B-10 will start, run great for a few minutes, quit, with a soft pop, then will immediately restart and repeat the same thing. I have tried a little troubleshooting as follows: Remove needle valve from under bowl. Fuel Trickles, not runs, out. Remove fuel line, good flow, around 6 ounces in time it takes to turn fuel shutoff under the tank. Assumed this means carb issue: Removed carb, no restriction in the fuel intake path. Disassembled carb, It was together good, gasket held well. float needle looked good. The only thing that didn't seem right was the float valve seat. It sticks above the carb base by an almost imperceptible amount (just enough to feel with a finger nail) Could this be just enough to make the engine starve for fuel before the float can open? Any ideas?

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firefoxz1
My rule of thumb is with the carb upside down slide in the needle, if you roll the carb over and the needle don't fall out you have a problem. Take some fine sand paper to the sides of the needle and also roll a piece into a barrel shape and clean the sides of the seat, then retry. With a full tank of gas the pressure on the needle is almost the same as with a fuel pump. Make sure your needle matches your seat, little rubber seat = short solid needle, and solid seat = needle with a rubber tip. Also if a rubber tip needle shows signs of indentation from the seat change it, that can cause it to stick.

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HubbardRA
You will have a major sticking problem if you have the rubber seat and also use the rubber tipped needle valve. The two pieces of rubber like to compress and wedge together.

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GWGAllisfan
I have the Viton tipped need, in the brass seat. Everything looks just like it should. It just seems like the fuel flow isn't coming soon enough to feed the engine. That it will sometimes run longer with choke half on tends to support this theory. I'll try the tests suggested and see. maybe a slightly higher float level may be needed. I know i have fuel to the carb (It pours out an open line), but doesn't pour out the lower needle valve like it should.

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HubbardRA
Randy, Have you checked the fuel line and the fitting at the gas tank? On my son's 64 Landlord we were having the same problem. I had to remove the shutoff valve on the bottom of the tank and replace it with a regular fitting to get enough gas flow. I then put an in-line fuel shut-off and filter. Works great now. His has the viton tipped needle and the brass seat. In fact, all the B/S carbs I own are viton tipped needles with brass seats.

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MrSteele
It does sound like a restriction somewhere between the tank and the carb. The screen on the valve in the tank may be clogged. Try blowing air into the tank through the fuel line. If that makes it work, there is something in the way. Depending on several circumstances, the line itself may be clogged with dirt and needs to be replaced. Is the filter clogged? What about the fitting at the carb? You have flow, it may not be enough. In the carb, have you set the float level? With the bowl off, turn the carb upside down. The float should be level with the needle closed in this position. If it is out of level toward the carb, flooding may occur. If it is out of level away from the carb body, it is too low, and will shut the gas off too soon.

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GWGAllisfan
Yesterday I was lucky enough to find a new carb gasket in stock locally. Last night checked all passages and parts, put the carb back together. It seemed like when I held it in normal position the float had to drop too far before the needle valve opened, so made just a slight raise in the float level. Put it all together, Bolted it on, and it started right up, ran fine, none of the problem showed up again. Don't really have a good theory for why, but willing to accept result for now. One oddity though, the engine seems to run best with the main high speed needle at about 1 1/8 turns out instead of the standard 1 1/2, but again, won't argue with results.....

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