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GWGAllisfan

Mysterious B-10 problem part 2

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GWGAllisfan
I was mowing with my B-10 today and it did something strange. At first it ran normally, but as it started to get warm, it would seem to be working much harder when going uphill or in deeper grass. After about an hour it got to the point where it would stall out while just mowing along in low grass, 2nd gear, level ground.:( Fuel tank had at least 2 inches in it. As shown in the link below, this particular engine seem to be magnetron converted, maybe not done right. I did decide just to see how it performed before I pulled the motour. [url]http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=64246[/url] From what I have read, the mis-timed spark would tend to create overheating, which would tend to increase coil resistance, making the spark even worse. Am I on track, or completely off base??

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B.Ikard
Randy, If you can get one of the clamp on spark checker tools thru briggs you can get a visiual on the spark in operation. I have one of the mysterious factory OEM electronic coils on my 1975 16hp and it works great (the one you saw when you came over). It is clearly not a magnetron conversion. I have never heard an explanation on how these early electronic ignition coils came about and never seen anything in the briggs service pubs on them. Brent

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Doll
Sounds like 1 of 2 things to me. Lean burn / starving for fuel, or over heating from clogged fins or a rat nest over the coil. If it were mine, I'd start it and check that it had good air flow over the head. Then I would start mowing until it acted up. Once it does, back the high speed jet out 1/4 to 1/2 a round. It should do 1 of 3 things. Clear up, run rich or not change. If it don't change, You have a fuel flow problem or a restricted jet.

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MrSteele
I'd tend to agree with Doll. At least, the toilets are susceptable to overheating and stalling when the fins are clogged. I've rarely had the problem with Briggs. A good blow with an air compressor should do the trick. I do that regularly, anyway, on all small engines to get the dust out, and when repainting, make certain that a good smooth coat of paint is on the fins to reduce the amount of dust able to collect there. That coat of paint also helps cleaning the fins later.

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MrSteele
Painting may not be the proper thing to do, but all the cast iron engines I have ever seen have the fins painted. Clinton used to paint them red, Briggs were usually black, and on some engines, were painted high heat silver. I have torn down many over the years, and way back when I was the first to do so, most were painted. A coat of paint makes cleaning much easier, as the dust does not 'grab' onto a painted surface as easily as it does to rough cast iron.

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MrSteele
"From what I have read, the mis-timed spark would tend to create overheating, which would tend to increase coil resistance, making the spark even worse." My father always ran his small engines ahead a few degreees, arranged by closing the points so that they barely opened, or, opened just enough to create a spark, and moving the mag ahead. The engines ran a bit hotter than usual, but, as his engines usually ran til they wore out, and worked hard all the time while wearing out, we could see no ill results in the extra heat. If yours is running out of time because of the mag being in the wrong position, that could create extra heat, but not the kind of heat to make it stop as you describe.

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GWGAllisfan
I have cleaned the head fins, checked the fuel delivery, made sure the tank is full, so if we get any rain this week and the grass will grow, I will test it and see if there is any difference. By the way, North Georgia is very dry, we badly need rain.

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GWGAllisfan
Ok it finally rained enough for the grass to grow, so I tried the mower again, after checking fuel delivery, and fin cleaning. This time it ran for about 45 minutes before it began to miss. It never completely stalled, just ran really rough. Observations When I first started, choking it would make it run rich with black smoke, but when it began to run rough, the choke had no effect. Angle of the tractor seemed not to affect it. At one point I sprayed some water on the engine to see if evapourative cooling would help, inconclusive. There was air over the fins, I could feel it with my hand in front of the head. I was able to get through the rest of the grass and when I parked it I pulled the plug, which was black, but lighter around the electrode.

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Ketchamized
GWGAllisfan, There is a plug chop test that you can do to determine what's wrong. Check this link out: http://faq.f650.com/FAQs/SparkPlugFAQ.htm#Plug%20Chop Usually, I do this with my mopeds and scooters. I'm not sure if it applies to tractors (Since they're 4-stroke engines) But I don't see why not... Basically, how to do it- buy a brand new plug in. Start the engine, rev it as high as you can, for 10-15 seconds, make it really hot. And while it's revved up, shut down the engine suddendly. This can be done by pulling the plug boot away or turning the key to 'off' position. Then immediately take the plug out while it's still hot. http://www.nightrider.com/biketech/spkplghnbook.htm The above link explains on how to look at plugs and determine what's wrong. According to your description, it sounds like your plug is oil fouled. Maybe when your engine gets hot, the seal becomes weaker and oil leaks into the crankcase and shuts down the engine. Too much oil, not enough gas? Or, there is too much oil in the engine and when it gets hot, the oil level increases, going over the 'spill proof' walls into the crankcase? This is based on my knowledge of the 2 stroke engines... I'm an expert on those, but 4 strokes, I'm still learning... So, whatever I just said may not apply. Then again, it may apply. Another thing I can think of- are your brakes adjusted properly? Transmission having a drag? What about the drive shaft? Anything rubbing against it? Bent? Starter/generator having a drag? That would put extra stress on the engine and cause it to overheat. Is your spark plug the right range for that engine? Is your governer set at 3,600 rpm's (factory setting) or is it set at higher rpm's? I read that the points has to be at a certain gap. I don't know what it is for yours, but when you rotate your engine, bring it to TDC. This can be done by turning by hand and when it feels at its peak, when it's hard to turn further- that's TDC. At that exact point, your points gap has to be at a certain gap. Mine's .015" Maybe your condensor is firing too hot. That's the best I can think of with my still learning knowledge but high common sense. Hope this helps. Best, Erick

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