Briggs 17.5 opposed twin will not restart when hot 42A707

[troy-built]

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

 

[mechanic mark]

Absolutely, when was the last time you removed blower housing, cover over engine, & cleaned cooling fins on each cylinder top & bottom? Do not use water, I use small dental like tools, small wire brushes & a Shop Vac to remove crud from engine. Using water will create electrical & mechanical problems.
Take a look at plugs & gap & inspect spark plug boots.
Post complete model xxxxxx, type xxxx, trim xx, code xxxxxxxx.

 

[troy-built]

Thanks for the reply.
I took it completely apart last fall to replace the pan gasket. It's clean as a pin as I don't cut grass with it anymore I just use it to pull a trailer. I just have started using it in the last couple of weeks that's when I seen it wouldn't start when hot. It doesn't have to be that hot either. I can let it run for lets say 5 min riding around the yard. You know I just thought of something. I had it sitting in the sun with the hood up yesterday and it had been sitting there for an hour. I tried to start it, nothing so I pushed it in the shade and 20 min later it started right up. So go figure.

 

[troy-built]

Now I did wash the entire mower last fall before I took it apart. The mower had been sitting in my shed for 10 years before I got it out to work on it. Looking for something to do you know.

The mower ran and started great when I parked it because of the oil leak.

 

[Scrubcadet10]

see if you can get it to fire on Parts cleaner or starting fluid when hot.

 

[troy-built]

see if you can get it to fire on Parts cleaner or starting fluid when hot.

Yep I tried that and nothing. It's not firing at all until it cools down.

 

[troy-built]

You know I was thinking about what was said about washing a mower.
I blow my mowers of every time I cut grass. And I wash them every 3rd time I use them and I have NEVER had a problem with them starting or anything like that.
I guess it could be from sitting so many years?

 

[Scrubcadet10]

Have you checked for spark when it's hot with an inline tester?
Being a flat head engine, it could be the valve clearances (Between the lifter and valve) have gotten too tight and only manifest the issue when hot (metal expands, decreasing the gap even more)

 

[troy-built]

I'm not seeing the model numbers and engine numbers in my crystal ball either
(must need a new crystal ball)

LOL I like that. I always say we need to contact Carnack. LOL

 

[troy-built]

Have you checked for spark when it's hot with an inline tester?
Being a flat head engine, it could be the valve clearances (Between the lifter and valve) have gotten too tight and only manifest the issue when hot (metal expands, decreasing the gap even more)

Now that's one thing I haven't tried but I will for sure. Thank you.

Would you know what the valve gap is on my mower? Numbers above. LOL