Popping=backfiring?
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I was having the exact same problem.... Rebuilt my old card, worked good for a bit then died. So one day i just went out and finally bought a reman card from advance. it was doing that pop noise too. I started by replacing all my hose's and fuel pump, and fuel filter. He helped but still did it. The I started adjusting my card, honestly I don't know how to adjust the card too well.. but that doesn't stop me. I idled the engine when it was warm and started to turn the mixture screw tight till it wanted to die then backed off, test drove.... changed but nada. repeated this untill i found the right mixture.. I am no professional, but have had expierence with single barrel carbs. It also could be a vacuum somewhere.
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From: Virginia
Lets get a better description of what's going on. It backfires through the carb. If you rev it slowly, does it backfire through the carb? Or does it only backfire when you goose the throttle? Have you driven it on the road yet, or is this just in the driveway?
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Reving slowly, I don't believe so. It won't do it at all if its in park or netural. It does it in a gear.
Yes I've driven it on the road. It has not a lot of power, and back fires upon acceration. I don't have a tach that works right now, so I can't tell you at what rpm.
Yes I've driven it on the road. It has not a lot of power, and back fires upon acceration. I don't have a tach that works right now, so I can't tell you at what rpm.
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From: Virginia
Well, you said it ran better with the timing advanced. I don't know about this engine, but I know others have occasional problems where the rubber on the harmonic balancer works loose, and the outer ring of the balancer slips. This throws the timing marks off. I wonder what would happen if you go ahead and turn the timing up till it seems to run good. If it starts good too, and the popping goes away, maybe the balancer has slipped.
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While that sounds possible, I don't know for sure it thats true with this engine. The balancer has a tooth on the crankshaft, and therefore the balancer can only go on, one way. Now the tooth could have broke, but I kind of doubt it. I'll check though.
As far as tuning, I'm assuming that the fly by the seat of your pants tuning of the carb is the only way to go. So...I guess we'll see if I can do that.
As far as tuning, I'm assuming that the fly by the seat of your pants tuning of the carb is the only way to go. So...I guess we'll see if I can do that.
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Alright. I drove it around today. I messed with the mixture screw. Turned it tight as far as it would go, then I brought it out until it ran right. It only backfires under accerlation from a stop. Accleration on a hill or anything like that, it doesnt. Nor does while normal driving. I haven't touched the timing yet.
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From: Virginia
Backing firing right when you hit the gas sounds like the accelerator pump is not working correctly. With the engine off, take the aircleaner off and look down the carb throat while you pushback on the throttle. You should see a strong stream of gas pour into the engine right when you move the throttle. If you can move the throttle a little bit before the stream starts, or the stream is a puny dribble, then it will run lean when you hit the gas, and give a terrible hesistation and it can cause the backfiring.
Also about the balancer, true the center has a key and it can go on only one way. But that's only the center hub. There is an outer ring on the balancer were the timing marks are, and it has no mechanical connection to the center part of the balancer except by molded rubber, somewhat like a motor mount. If this rubber gets old and oil soaked, it can come loose and the outside of the balancer can work it's way around, even though the center is still keyed to the shaft.
Also about the balancer, true the center has a key and it can go on only one way. But that's only the center hub. There is an outer ring on the balancer were the timing marks are, and it has no mechanical connection to the center part of the balancer except by molded rubber, somewhat like a motor mount. If this rubber gets old and oil soaked, it can come loose and the outside of the balancer can work it's way around, even though the center is still keyed to the shaft.
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Originally Posted by Franklin2
Backing firing right when you hit the gas sounds like the accelerator pump is not working correctly. With the engine off, take the aircleaner off and look down the carb throat while you pushback on the throttle. You should see a strong stream of gas pour into the engine right when you move the throttle. If you can move the throttle a little bit before the stream starts, or the stream is a puny dribble, then it will run lean when you hit the gas, and give a terrible hesistation and it can cause the backfiring.
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From: Virginia
Make sure to check it first, there is no use taking the carb apart if it's alright(you didn't say).
If it's not right, there are several adjustments that should be outlined in the rebuild kit. The rebuilt carb should have been already adjusted.
What's it look like? Is there hardly no fuel squirting out, or is there a big delay before it squirts?
If it's not right, there are several adjustments that should be outlined in the rebuild kit. The rebuilt carb should have been already adjusted.
What's it look like? Is there hardly no fuel squirting out, or is there a big delay before it squirts?
Are you sure that the plug wires are installed in the correct order?