QuestionOk I have rebuilt the carb and it still does the same thing. I tried the hand over the intake and it didn't make any difference. My newest findings is that when I pull start it, it seems to be back firing/spit through the carb and out the air filter. It seems like it is sucking in and exhaling though the carb and air filter. The plug is still fairly dry but is getting a little wet. Still if I poor gas in the spark plug hole it will fire and run for a minute. Also if I choke it and put the throttle on low speed I can get it to start after about 10-15 pulls, only for it to run for about 2-3 seconds and die out. Also i have gas leaking from the bottom of the carb drain hole. It seems like there isn't enough vacuum to pull the gas into the cylinder and instead it is just leaking down the throat of the carb and eventually leaking out the bottom. I called a local parts dealer for B&S and they seem to think its the valves. They seem to think I may have a burnt valve or blocked valve or one that not seating properly. Does this sound like my solution? I don't what to take it in for a valve job it that's not the problem. They gave me the name of a guy close by that can do the valve job. I was really hopping to fix this on my own since that's half the fun of restoring this old garden tractor back to plowing condition. By the way I identified the motor as being a 8hp the model number is 190402 type 0652 the carb is a 2 peice flo-jet. Thank for your help.
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Followup To
Question -
I have taken the carb back apart and cleaned it in a solution to see if I could loosen anything up. I blew all the holes out and probed them with a very small wire. I am on my way to get a carb rebuild kit in just a few moments. I will rebuild the carb and try it again. If it dosn't work then I will try puting my hand over the carb intake. Wouldn't that be the same as using the choke? By the way before the question comes up the compression is good. Thanks for all the help. I will let you know my findings.
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Followup To
Question -
I just purchased a 1955-1965 Speedex tractor that has a Briggs and stratton engine on it. I don't know the model or am I sure of the HP. I think it's between 5-8hp at a guess. There are no numbers that I can find on it. I think that it has the flo-jet carb though and I think it may be a L-head?. It does have a coil for the egnition. My problem is that I can pull start it and it will fire for about 3-8 seconds if I pull it long enough. I can add a teaspoon of gas to the carb and it will run until the gas is burnt out. Fuel line is flowing freely. So I think my problem is the carb. So I took the carb apart and cleaned (Carb cleaner and high pressure air) it and put it all back together and still the same thing. Both seting screws are set at 1.5 turns out from seat. I am using this as a starting point. Since it seems I'm not getting fuel I took the carb back apart and checked the float leval and made some adjustments. I think that the float should be level when upside down. I put it back together and still the same thing. I'm stumped, can you help me? any suggestions? P.S. the plug is new and gapped at .025 also it's dry not fouled.
Answer -
If you hold you hand over the carburetor throat as you start the engine will it run? Basically you are cutting all the air off from the carb enriching the fuel mix.
Let me know.
Eric
Answer -
Placing your hand over the carb seals better than the choke. Most choke butterflys have a small hole in them to allow some air.
Since the engine is so old I would also inspect the throttle and choke shaft for wear.
Eric
AnswerThe backfiring is either caused by ignition timing, electrical, maybe the flywheel key or points.
Or it could be caused by the valves. I have seen Briggs valve seats come out.
For many years Briggs manuals had you check the compression by removing the front engine cover and rotating the engine backwards. If the engine snapped forward on the compression stroke they considered the compression to be good.
Have you done anything with the points?
The gas leaking out of the bottom of the carb is caused by the taper on the high speed jet. You can use an old jet, grind off the threads, and then use some find lapping compound and the old jet to lap the taper. This will usually fix the problem.
On older engines, the head gasket can be reused if you want to check the valves. It's not recommended to reuse the head gaskets but I have done it when I had too.
Let me know about the points, and I would check you flywheel key. Since the engine will fire I doubt this is the problem but I would check.
Are the intake gaskets in good shape? Did you check the throttle shaft for wear? This can cause an air leak.
Let me know.
