Briggs 17.5 opposed twin will not restart when hot 42A707

I want to thank everyone for chiming in that has given me some ideas. That's what I was hoping for. I'm going to go work on it for a while and check the compression when it's hot and won't restart. I'll be back later to tell you what I find out.

Many thanks again to all.
 
troy-built said:
I have a Briggs 17.5 opposed twin that will not restart when hot. I've changed the coil twice it's getting fuel but today I finally figured out it's not firing. It's a 42A707 motor. Now once it cools off after about 30 min it will run like a top until you shut it off. It starts right up when it's cold.
It's sounding like a wire is breaking down if it was a car but i don't know where to look?

Anybody? I don't know what else to look at?

Thanks
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People, go back and read.
 
beg said:
my guess is your coil is bad had the same problem on two of my Toro ccr1000 snowblowers wound not start after being warmed up
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I tried a new coil and it did the EXACT same thing. Is it common to get a bad new coil?
 
If the engine is not firing, valve clearances shouldn't be of concern until it is firing. You can check the compression with a gauge while cold, then when hot, to see if a valve gets lifted when hot. Coils are prone to heat related failure, causing problems that can resolve when they cool. As they expand and contract with the temperature, damaged insulation can cause them to short out, or an internal broken wire can open the circuit, etc. Engine heat transfers from higher to lower temperature areas when the engine is stopped because the air flow stops.

I've had trouble with a flooding carburetor when the engine was stopped. The carb is between and above the cylinders and heats up when the engine is stopped, this caused the gasoline to boil over into the intake manifold. Check the plugs to see if they are wet when it doesn't start when hot. After it sits a few minutes when hot, look for fuel puddling in the intake manifold using a light, by looking through the carburetor w/ the choke and throttle wide open. I lowered the float level slightly to resolve that problem. But again, not a lack of spark issue. Systematic troubleshooting helps pinpoint causes for problems.
 
troy-built said:
Are you saying to wash a mower or to not wash a mower? That wasn't clear. I did answer his question by the way.

I myself will continue washing my mowers and everything else I own. It's NO different than washing a motorcycle to me. I have a 2013 zero turn that looks as good today as it did the day I bought it.

Water isn't the problem with my mower I'm sure it's just age.
Thanks
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Recommended to NOT wash a mower. Rust, corroded wires and connectors and so on. Power washers could get water in the oil sump with all that pressure. Key not working, corroded grounds to name some more.

Use compressed air, ScrubCadet 10 brushes, baby bottle brushes, degreaser then blow off and so on.

Use what ever method you have to clean the engine YEARLY or more if you scalp or bag. Some baggers dump a lot of grass on top of the engine.
 
troy-built said:
I have a Briggs 17.5 opposed twin that will not restart when hot. I've changed the coil twice it's getting fuel but today I finally figured out it's not firing. It's a 42A707 motor. Now once it cools off after about 30 min it will run like a top until you shut it off. It starts right up when it's cold.
It's sounding like a wire is breaking down if it was a car but i don't know where to look?

Anybody? I don't know what else to look at?

Thanks
Click to expand...
I am thinking about "what is the obvious"?
On my old B&S motors I create a ground to stop the sparkplug from firing. There is a kill switch for same with a small wire going to a ground.
Today's mowers have the "deadman switch" (maybe the wrong name) which requires one to hold the lever against the Push Bar. When released; the mower stops. First place I'd look is the complete deadman system, handles, springs wires to ground out the ignition. It could be that the ground wire switch is too close to the actual ground, thus the mower won't start when everything is hot. I'd also look for bent pieces around the springs, small wires and cables. Also look to see if the ground wire has too much insulation cut back on it (or the wire is loose), and the hot motor makes the switch get too close to a ground.
 
More then likely the gap on the points is off, too close.. when it heats up the points expand closing the gap too close to make the spark(seperate enough for the coil to build up voltage)..

I had the opposite problem with my briggs opposed twin, the points wore down so much that the gap was too large for a strong spark, so if it was 90 degrees outside and it was sitting in the su it fired up ran weak for a few minutes then ran strong as could be once warmed up. I had to dig deep into my car knowledge (back to the 1960's) to figure it out.. Of course I did everything you did, cleaned everything, replaced plugs coils, wires, tried starting fluid etc etc.. and it turned out to be the stupid points..
 
troy-built said:
I tried a new coil and it did the EXACT same thing. Is it common to get a bad new coil?
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Depends if it's an OEM Briggs part or aftermarket? I've used a few aftermarket coils
slomo said:
Recommended to NOT wash a mower. Rust, corroded wires and connectors and so on. Power washers could get water in the oil sump with all that pressure. Key not working, corroded grounds to name some more.

Use compressed air, ScrubCadet 10 brushes, baby bottle brushes, degreaser then blow off and so on.

Use what ever method you have to clean the engine YEARLY or more if you scalp or bag. Some baggers dump a lot of grass on top of the engine.
Click to expand...
????
 
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