Craftsman No Start

[lefty]

Mower
Craftsman 917.377120

Briggs
12S505 3856 B1 070427 FA

So I had this machine come to my garage from a neighbor with a no start. The machine ran last year but ran poorly per owner. The primer bulb had a hug crack in it, which explained the no start. This is an overhead valve engine and the valves were way out of wack. 4 times the clearance on both so I adjusted those to spec.

I opened the carb and found one of the welch plugs floating at the bottom of the bowl. I pounded it back to a dome shape and reinstalled it. (not sure if this is an acceptable technique. Read ahead).

I cleaned the carb and assembled. The machine ran great. I ran it for a bit and gave it back to my neighbor. He took it out today and cut 80% of his property and then went into a real crappy area. Huge amount of dust and dirt per his report. The machine stalled and would not start again. It would start / sputter for a few seconds and than stop.

He brought it back thinking the dirt was the problem. A few hours later, I got a chance to look at it. I started it on the first pull and mowed a bit. Feeling satisfied, I shut her down and wheeled her into my garage. I then went to start it again. Same problem, sputtering, no start. Run for 2 seconds and stall.

My first idea was gas cap vent as this seemed very similar to problems I've seen on snow blowers, which turned out to be gas caps. So I happened to have an extra cap from the same tank... what I surprise? (will be funny to anyone who has been following my briggs crank thread).

So I timed fuel flow for the cap and the spare I had. The spare drained the fuel in 1/2 the time as the machine's cap. So I changed caps. I started the machine and let it run for about 10 minutes as I sat on the tailgate of my truck with a beer patting myself on the back.

But sure enough, when I shut it down and tried to start her again, Same symptoms. So I took apart the carb and you guessed it, I found the welch plug floating at the bottom of the bowl again.

So I'm assuming that's my problem. Sorry for the long winded explanation but I wanted to be sure I included every detail....plus, I may not have stopped at "a" beer.

And given my recent failures, I'm having self confident issues.

[Fulltilt]

The welch plug should only be a baffle of sorts for the bowl vent, shouldn't affect it. If you look, the casting has a big slot in it, right? Of course you might have a carb with the two welch plugs, so if it's not the vent plug, then yes, that could be it. I've redomed them lots of times, but I usually run a small bead of epoxo-88 ( epoxy) around the rim before install, even on new welch plugs. I use a toothpick to sparingly apply the epoxy. Your local napa might have a welch plug assortment kit. But the epoxy trick has always worked for me.
Wouldn't hurt to replace the needle and seat, could be sticking intermittently.Obviously, make sure the jet is clean. The air bleed in the throat clear?


As an aside, I have to say, I can't ever recall running into a small Briggs with the valves that far out of adj. Something doesn't sound right, there .

[lefty]

This one does have two welch plugs. I'll try reinstalling with epoxy maybe. Looks like an OEM carb is only about $38. I may suggest that to the owner.

Not sure what to say about the valves. I measured about .015 gap on both when I first removed the cover. According the engine manual, they should be between .004 and .008? I set them at about .005 and it ran brilliantly.

You mentioned that one plug was for the vent and the other may cause the problem? What is the other welch plug's purpose? Any tips on identifying which one of mine fell out?

[NO0C]

Interesting you should mention that. I just had my son's, new to him, 2 years old to the rest of the world, B&S 103M02-0002-F1 on a SP cheapo Snapper (Wal-Mart special) here to clean it up and give it the spring once over. First thing was to check valve clearances. Like you, the spec is .004-.008, both int and exh. Both were .020+. Really? 2 years old and that much wear or were they never right? I'm not sure how it even started or ran with any power. Sure started and ran great when I got them set. I'm sure this engine has not had the best of care as the oil capacity is 15 oz. and I drained well over 22 oz. out of it and the air cleaner element and cover were gone. Some people's kids!

This is one of those 675EXi series that never needs the oil changed. Yeah, right.

Manual says 'Check and Add'. 'Oil change is not required'. WTH?

Not sure what to say about the valves. I measured about .015 gap on both when I first removed the cover. According the engine manual, they should be between .004 and .008? I set them at about .005 and it ran brilliantly.

[RoyM]

Briggs claims that with new materials and production methods the oil should never become so contaminated that it needs to be changed, just top up as necessary. Of course regular air filter maintenance becomes critical so your son's machine doesn't qualify. This is for people who don't maintain their equipment, just gas and go, but the cheap box store mowers these engines are used on are generally done after five years so it really doesn't make a lot of difference. Just a marketing ploy.

[Fulltilt]

Briggs claims that with new materials and production methods the oil should never become so contaminated that it needs to be changed, just top up as necessary. Of course regular air filter maintenance becomes critical so your son's machine doesn't qualify. This is for people who don't maintain their equipment, just gas and go, but the cheap box store mowers these engines are used on are generally done after five years so it really doesn't make a lot of difference. Just a marketing ploy.

Yep, much like the " Overhead Valves " .

[lefty]

I'm sure this engine has not had the best of care as the oil capacity is 15 oz. and I drained well over 22 oz. out of it

Funny you mention that. This machine had barely any oil in it when it arrived. Fortunately, I had a successful leak down test so I guess no harm no foul. But maybe poor maintenance can impact the valve clearance over time?

Anyways....I spent a little more time on the welch plug this time. I drilled a hole slightly larger thank the plug into a piece of aztec. Not to deep, just made a dome shape in it and then pounded (gently) the plug back into a dome shape and reinstalled as usual. I want to see if I can get it to stay in there for a while to at least diagnose the problem.

[NO0C]

No doubt about it. Lack of lube causes wear everywhere, even on the rocker to valve stem surfaces.

But maybe poor maintenance can impact the valve clearance over time?

[lefty]

So I got a new carb for this one. I had no luck getting the welch plug to stick and my neighbor elected to go with the new carb route. I got an OEM carb for it and am still having the same problem. Machine starts on the first pull, runs great until I shut it down. Ran it for 20 minutes one day and 10 on another, mowed some grass. Once I shut it down, I can not get it started again. With primer and may start to start but then dies. I've checked the fuel flow from the tank and that looks fine. Like I said, new carb.

I'm stumped. It feels like a fuel delivery problem to me as I can get it to fire off a few revolutions with primer but she just won't stay running. Once she cools down, she'll start again but the same problem. Any help at all is appreciated.

[KE4AVB]

Try changing the ignition coil. Sounds like electronics thermal breakdown.