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Old 03-12-2002, 07:15 PM
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Question flattie misfire?

I recently bought a new coil and distributer (mallory duel point) for my 53 flathead. i was having low end bogging problems. i thought that was the problem. i also rebuilt the carb. thinking that was it. because the right jet was dripping instead of spraying. well turns out it still does. could that be the problem? it also backfires now at highter revs. do i just need a new carb or something else? thanks.

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Old 03-13-2002, 01:02 AM
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Cool

im no expert but, if part of the carb is driping the fuel insted of spraying it,it could be getting to much fuel and not getting a chance to burn it, this could be why its backfireing at high revs,a new carb may be whats needed, but if you could get the one part of the carb it could be cheeper!this could also have been why it was getting bogged down!
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Old 03-13-2002, 12:29 PM
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I am assuming you are running a 2bbl carb, but I don't know if you're using a stock fuel pump or an electric pump. Those old carbs were pretty sensitive to fuel pressure. If you're using an electric pump, the pump my be loading the carb-ie the pump is putting out more pressure than the needle/float can shut off. If this is the case, a fuel pressure regulator needs to be installed between the pump and carb. Set it around 2 1/2 to 3 psig. Doesn't sound like much when you compare it to todays carbs, but those old flat-motors didn't require a lot because in most cases the rpm wasn't as high as todays.
Pull a couple of the spark plugs (one from each side) and check out the condition of it. A chocolate color is OK. If it's black and wet-sooty the engine is running too "fat" (rich). You mentioned that the engine back-fires at higher rpm. If you mean through the exhaust system, It could be; 1. the engine is too rich and gas is burning in the exhaust, 2. The engine timing is too retarded (does it run on the hot side?) or 3. the distributor cap got dirty and carbon tracking is allowing spark to travel to the wrong spark plug terminal.
These are just a couple of ideas to get you started. Good luck! Flatheads Forever!
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Old 03-13-2002, 08:10 PM
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hey thanks guys for the resposes. i am running an electric fuel pump. and i do have a regulator set at three pounds. i also have the spark advanced around 20-25. i think. its 3/4 an inch. the width of a peice of masking tape. (something flat head jack said to do?) i don't want to go out and spend money on a rebuilt carb if it's something i can fix. but i'll check out the plugs. thanks.
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Old 03-14-2002, 06:02 AM
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All good advise. The plugs first.But i hate to even say this cause you just bought it,but those daul point mallorys were a real pain.Make sure the cond are tight and the points did not close up on you(in time they will,and i would change it over to a pertronix unit with out points) Is it on 12 volts? You got a ballast resistor before the 12 volt coil?? Or even a internal resistor coil?? After that i would do a leak down test.Its easy and a much better way of telling engine cond than a comp test. Good Luck i cant wait to find a nice home for my 43,000 mile flat motor.(no it aint 4 sale LOL just needs a good place to live)
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Old 03-14-2002, 11:34 AM
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Aw shucks Phat! I thought the flattie was an orphan. I was going to take it in just so it wouldn't feel bad!
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Old 03-28-2002, 09:21 PM
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This may sound dumb, but make sure your plug wires are going to the right plugs.
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Old 03-28-2002, 11:00 PM
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Just a thought.Im not up to power on the flat head carb. but did you say it was dripping out of the venturer tube ? Id go back & recheck the float level. I know sometimes those little critters reak havic on a carb & me.just a suggestion. any thing to save a few bucks & on a low end bogg try increasing accelerator pump shot. hope this will give you some ideals . roll on wrenchturner
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Old 03-28-2002, 11:10 PM
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Just a thought.Im not up to power on the flat head carb. but did you say it was dripping out of the venturer tube ? Id go back & recheck the float level. I know sometimes those little critters reak havic on a carb & me.just a suggestion. any thing to save a few bucks & on a low end bogg try increasing accelerator pump shot. hope this will give you some ideals . roll on wrenchturner
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Old 03-30-2002, 05:41 PM
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Dripping through the venturi feed usually means you have a plugged air jet or emulsion tube.
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