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Is it flooded?


proteus

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I have a Simplicity Broadmoor 728 with a Briggs 8hp engine. The engine starts cold after several cranks. After the engine is good and hot, if I turn it off it won't start again for another 30 to 60 minutes. Just in case you were thinking, I've replaced all of the gaskets. I cleaned the cooling fins. I adjusted the carb (float is in good shape), new fuel line, spark plug, coil, points, condensor, etc... Is the engine flooded or is it something else? Also, if anyone has a Briggs model 191700, can you post some pictures of your governor linkage and throttle linkage setup. Thanks.
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Check to see if there is sufficient clearance in the exhaust valve. I have had engines that completely quit running after a short time of operation. Would re-start in 15 minutes or so. Found little or no clearance in exhaust valve.
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When it fails to start try taking the spark plug out and see if it's wet with gas or dry. If it's wet then you have a carb problem or something's wrong with the spark. To check the spark just put the plug back on the plug wire but leave the plug sitting on top of the cylinder head. Crank it over and see if the spark plug is sparking. If not you have a problem with the points or condenser or the coil. If you have a compression gauge you could also check the compression when the engine's cold and check it again after it warms up. If there's a big difference then you may have valves out of adjustment or worn out piston rings. If the spark plug is dry then you have a problem with fuel not getting into the engine. Bad carb, plugged fuel line, vacuum lock. Best of luck finding the problem...
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My guess is the exhaust valve being too long. I have received several thrown away engines that I used for several years after shortening the valve. Normal wear on the seat is the problem, the only way to adjust is to remove that valve and grind the stem until you have about .020 clearance.
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The exhaust valve issue seems a bit extreme for an engine that doesn't have that many hours on it. Yes, it's old, but it's been sitting idle most of it's life. Humor me a bit on this one.... Could it be a bad gas cap/gauge? This has one of those caps with the cork float. The seal is bad on the cap, the needle gauge is rusty, the glass cover is missing and I had to remove the cork float because it was deteriorated. I have a new one on order but I searched the forum and found a thread where a bad cap was causing problems. Reminder: If anyone can post pictures of the throttle linkage assembly on their 191700 engine I would appreciate it. I don't see anything that resembles mine in the B&S repair manual.
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Rod and MrSteele, Where do I measure the exhaust valve clearance? I took the valve cover off last night, turned the flywheel ccw until I hit the compression stroke, had my feeler gauge ready but couldn't readily see where to measure what from what? The B&S manual is horrible. No help at all.
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With the valve cover off, you should be able to see the end of the valves. The gap is measured between the end of the valves and the lifters. Slide your feeler gauge in the space (if there is any space) between the valve stem and lifter to check clearances. The lifter is the metal rod extending into the chamber from the crankcase. The valves have to be in the closed position to check clearances. Check for clearance. If there is none, which might well be the case, then a fairly simple job will be in order to repair. At least, I think it is simple. If you have no experience at all with the interior workings of engines, the job should likely be trusted to your favorite shop.
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I don't see the end of the valves when I remove the cover. I see the springs holding the two valves on one end and on the other I see the valve go right back into the engine. I don't see the tappet moving into view so I don't see a gap to measure. The full length of the rod spans the entire width of the compartment. Is the gap supposed to be between the valve and the tappet?
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The spring is on the valve. The tappet is the piece that goes into the engine to mesh with the cam. The gap should be just beyond the keeper at the end of the spring. If you don't see a gap with the engine rotated to a position where the valve is definitely in the fully closed position, then there is your problem. I think the gap should be around .008 on the intake, and .014 on the exhaust. You should look up the exact specs for that engine to be sure. I don't have a book handy at the moment. Usually a couple of thousandths variation is allowed. As I said before, I have found this on a couple of engines. One of them was a vertical shaft 8 hp B/S like yours. Take a screwdriver and compress the spring a little to open the valve and you should see where the gap should be. On most of these engines, there is no adjustment other than filing the lifter and/or valve stem to get the clearance. I just pry the pieces apart and insert a small file. Then I release the the tension and file both pieces at the same time. Don't go overboard with the filing. Do a little, then check the clearance, then repeat as necessary. This is a very simple filing operation and should only take a few minutes, with no expenditures for parts, as long as you have not messed up the gasket on the cover. If the gasket is not broken then I usually just put a thin coating of gasket sealer on it and re-assemble. If it is broken, then you will need a new gasket.
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I checked out the gap this afternoon and it is within specs on both valves. I noticed that the valve cover (breather) has some oil dripping from it. Is this normal? Anyway, I got the engine going for about ten minutes and adjusted the carb mixture screws then went to mow the grass and after about a half hour the engine began backfiring. Once in a while fire would shoot from the muffler during a backfire. Then slowly it began to lose power and backfired a few more times before stalling. I couldn't get it started again before draining the battery. What could be causing this? I have spent hours on this motor and am really stumped. I really want to avoid taking this to the pros. I usually do all of my own work and get satisfaction out of a job well done by me.
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I would guess that the exhaust valve seat is loose. If so you may be able to peen over the edge around it to hold it in.
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When I hold the carb upside down the float is parallel with the carb body. While upside down no air escapes when I blow through the fuel inlet. As for the valve seat, the valves appear to seal correctly when I took the cylinder head cover off. Their was white carbon on the valve face. I read on this forum where someone bought an after-market coil and had this kind of problem then put the old one back on and everything was fine. Could my NAPA coil be causing this?
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After reading all of the posts. I was just about to ask What about the coil? But I see you may be headed in that direction.
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Sounds to me like the fuel mixture is going lean after it has run awhile. Check for a plugged gas cap vent among other things. Could also be crap in the fuel tank, fuel line, and/or carburetor. My 2 cents,
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Checked things out this evening and I am able to confirm that I'm not getting a spark from the coil after the engine stalls. If I wait a couple of hours I will get a spark. Can a coil stop producing a spark when it heats up and then start working again after cooling down? Is this common with the NAPA equivalent and should I get a Briggs coil online?
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Hi, You mention the MAPA coil. Have you converted this to battery ignition? If so be sure that you have a coil that doesn't need a ballast resistor. Regular automotive coils are really 8 to 9 volt coils and use a ballast resistor to drop the voltage to this level. In an auotomotive application they use a bypass circuit to connect the 12 volts directly to the starter when the engine is cranking. This provides a hotter spark when cranking. After the starter is disconnected the voltage is supplied through the resistor again. The reason for this is that the points will have a short life if the coil is run continuosly on 12 volts. I have probably replaced and thrown away 50 of the automotive coils that had been installed on golf cars that didn't run right. You need a coil that does not need an external resistor. If you have a regular magneto coil, it is not uncommon for them to occasionaly fail after running for a while. If you have points yet, be sure the flywheel key is not sheared. With points this will cause no spark, coils with electronic ignition have spark regardless whether the key it sheared, it will just be out of time. Mote the washer under the flywheel nut is a belvedere nut, and MUST go on so the outside edge bears on the flywheel and the high center is against the nut. Al Eden
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Great information Al. I'm not using an automotive coil. The guys at NAPA just x-ref the Briggs part number and gave me a coil that looks pretty much identical. Ever since though, I've been having trouble. Tried the old (original) coil but it's fried. The flywheel key is not sheared. I've had the flywheel off and on a dozen times in the past two weeks and it looks fine. The info on the washer is good to know. I just took a guess on that and had it right. I'm off to NAPA to replace the coil. I'll give an update later today.
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Got 'er fixed today. It was the new coil. I've been chasing down this problem for two weeks. I guess when the new coil heated up from the engine, it would stop producing a spark. When it cooled down the coil would work again. I replaced the coil today and she runs like a dream. Thanks for everyone's help.
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PS- Several of my friends report NAPA electrical components are poor, (chinese,mexico) I have had condensors bad when new! Try purchasing from your local Small Engine dealer, pay abit more, but worth it.
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