Lawn mower question. ;-)

hunt4570 · Jul 29, 2015

Well my Kubota is in the shop, so can I ask a lawn mower question?? Ah, good... here goes..

Troy bilt wide cut walk behind, 8 1/2 hp Briggs... old!! I've had it about 17 years and it was used when I got it! Billions and billions of miles!

So when I go to use it, turn the key on, choke it and starts in 1 or 2 pulls usually, mow for say an hour or something and turn it off to get a drink, go pee, whatever, come back to it and IT WILL NOT START to save my soul!! It will start with lots of pulls and a can of starting fluid. Other than that its a no go till it cools all the way off! Oh, it has new oil, air filter and plug in it!

HELP!!!

Quebecguy · Jul 29, 2015

Why don't you try changing the fuel filter?

hunt4570 · Jul 29, 2015

Quebecguy said:
Why don't you try changing the fuel filter?

Didn't realize there is one in there, is there?

I'll have a look see tomorrow..

Coyote machine · Jul 29, 2015

Sounds like it binds up when hot. Try pouring some Marvel Mystery oil into the carb, and the crankcase too. Start it up and let it run some, then leave it to cool down. Do this, the warm up/cool down a couple of times and see if there's improvement. I did this with an old Mcculloch chain saw and it worked great. Same symptoms as your Troy built. Old stuff gets gunked up, gasoline varnish, rings sticking to pistons etc.

hunt4570 · Jul 29, 2015

Coyote machine said:
Sounds like it binds up when hot. Try pouring some Marvel Mystery oil into the carb, and the crankcase too. Start it up and let it run some, then leave it to cool down. Do this, the warm up/cool down a couple of times and see if there's improvement. I did this with an old Mcculloch chain saw and it worked great. Same symptoms as your Troy built. Old stuff gets gunked up, gasoline varnish, rings sticking to pistons etc.

I'll give it a shot!

Quebecguy · Jul 30, 2015

I'm sorry I don't know the details of your Briggs motor but I do suspect that pretty well every internal combustion engine ever manufactured has some means of filtering the fuel whether it is a disposable element or a screen or gauze that can be cleaned.
The 18 HP Craftsman lawn tractor that my girlfriend inherited about ten years ago exhibited the same symptoms as your machine: almost impossible to start when hot. This past May when I tried to start it after its winter hibernation it would turn over but not fire. After a bit of poking around I discovered, after removing the in-line filter, that I could not blow through it. I replaced the filter with a new one and the tractor started right up and guess what. The hot starting problem has disappeared too. I sawed the old filter (which was probably the original one installed at the factory twenty some years ago) in half to see what was plugging it but to the naked eye it looked just fine. I suspect modern gasoline breaks down quicker than the old stuff and microscopic blobs were causing the problem - who knows?
Another thought on difficult hot starting: when old British motorcycles with Lucas magnetos have this problem it is almost always the fault of the condenser and replacement of the condenser solves the problem. When was the last time your Briggs had a "tune-up"?

hunt4570 · Jul 30, 2015

Well , out there looking at this thing this morning... one gas hose directly from tank to carb, no "in line" filter. no mention of a filter in my mower manual, or the Briggs engine manual. Looks like hose attaches to tank via molded boss on tank, nothing removable.. looks like nothing removable on carb side too.

Tune up a couple years ago... I think ;-)

Also, my Briggs manual says (according to model number) it has a vertical flo jet carb... and says nothing about that particular carb type in the carb section at all! Can find NO adjustment (needles) anywhere on carb at all, just idle speed!

CORECTION: Found one adjustable needle, I believe high speed, it doesnt make much of a change turning it at speed, and none at all at idle.. in fact I can turn it till is seats and has no effect.

Coyote machine · Jul 30, 2015

So cut the fuel line, snip off a short section, go to local lawn mower shop and get a fuel filter with ends that fit your fuel line inside diameter and two hose clamps and install the filter with the tiny arrow facing the carb.
Still do the Marvel Mystery oil thing as suggested, and you're good to go. Since you're not sure of the last 'tune-up' decade, change out the spark plug too, and maybe do an oil change while you're at it, including the oil filter if it has one. Keep a record on the wall of when you did what for future reference.

JeremyK5 · Jul 30, 2015

Have you tried using an inline spark tester when the engine is cold, and comparing the strength of the spark to when it is hot and won't start? The style I like to use on small engines look like this- https://www.stens.com/752-329-inline-spark-tester

If the magneto/coil is getting weak and starting to fail, they usually fail when hot.