No spark

[jbradley]

Last fall, I went to use my 948 after it had been unused for a couple of weeks, and found that I couldn't get it to turn over. I took out the spark plug, and it turned over without any trouble, which told me that the exhaust valve was stuck closed. After covid in the fall of 2020, I haven't had as much stamina to do anything, so I put off working on it until recently. The valve came unstuck with some light hammer strokes, and the engine started fine afterward. I left it running to burn off the gas (I always use non-ethanol containing gasoline, and add sta-bil in the fall, not knowing when I'm going to last run the equipment.), and when I came back outside, it was no longer running, but still had fuel. When I tried restarting it, it had no spark. After watching numerous YouTube videos, purchasing a spark tester, and doing various troubleshooting tests, it finally dawned on me last night to look at the clutch lock and safety switch. The clutch clip had somehow come loose and disengaged the safety. After reengaging the clutch, the engine started fine! Sometimes you create your own big problems, because you didn't look for the simplest solution, first. Hopefully, I can get my garden tilled this afternoon.

 

[ROUSTABOUT]

KISS method. Learned in military.

 

[DJ54]

If ever the ex. valve starts sticking again when running, get a small container of Marvel Mystery Oil. Add prescribed amount in the crankcase, and in the gas. Briggs engine from the mid 70'swere notorious for the exhaust valve sticking when it got hot, and under load. Back when it came in a metal quart can, 1 cap full in the gas tank remedied the problem. A handy piece of info I got from the machine shop where I had engine work done.

I'm not much on mechanic in a can additive, but this stuff works.

 

[jbradley]

If ever the ex. valve starts sticking again when running, get a small container of Marvel Mystery Oil. Add prescribed amount in the crankcase, and in the gas. Briggs engine from the mid 70'swere notorious for the exhaust valve sticking when it got hot, and under load. Back when it came in a metal quart can, 1 cap full in the gas tank remedied the problem. A handy piece of info I got from the machine shop where I had engine work done.

I'm not much on mechanic in a can additive, but this stuff works.

I actually added a bit of seafoam to the gas and oil. I still haven't gotten my garden tilled. I put the finishing mower with grass catcher on it first, to feed some lawn clippings to my goats. It ran good for about 5 minutes, then bogged down. After cooling, it was a repeat of the same. I replaced the coil, and don't get any spark with the new coil. (The clutch/safety is locked. ) My 732 needs some engine repair or replacement, so I'm going to pull the coil off of it and see what I get. It's frustrating.

 

[ROUSTABOUT]

If ever the ex. valve starts sticking again when running, get a small container of Marvel Mystery Oil. Add prescribed amount in the crankcase, and in the gas. Briggs engine from the mid 70'swere notorious for the exhaust valve sticking when it got hot, and under load. Back when it came in a metal quart can, 1 cap full in the gas tank remedied the problem. A handy piece of info I got from the machine shop where I had engine work done.

I'm not much on mechanic in a can additive, but this stuff works.

I always wanted to try some of them JC Whitney engine rebuild pellets in a can.

 

[DJ54]

I actually added a bit of seafoam to the gas and oil. I still haven't gotten my garden tilled. I put the finishing mower with grass catcher on it first, to feed some lawn clippings to my goats. It ran good for about 5 minutes, then bogged down. After cooling, it was a repeat of the same. I replaced the coil, and don't get any spark with the new coil. (The clutch/safety is locked. ) My 732 needs some engine repair or replacement, so I'm going to pull the coil off of it and see what I get. It's frustrating.

For my purposes, Seafoam works great to keep the fuel system clean. I got that suggestion to use it either here on this small engine forum, or on another tractor forum. I couldn't figure out why my 2 Wheel Horse 310-8's were hard to start in the Spring, then later through the Summer if they sat for a week or so. They would start eventually if you kept cranking them over. I was informed that there is a small check valve ball in the carb that can get sticky and not seat properly, and let fuel drain back to the tank in the rear. Just had to keep cranking until the fuel pump pumped gas back up to the engine. It would start fine if it sat for maybe 3 days, after that, crank until it started.

I was informed to add the Seafoam as directed would cure the problem. Right as rain, it did fix the problem. I still use it every now and then but when Sta-bil came out with the Sta-bil 360, which stabilizes the fuel, plus cleans the fuel system like Seafoam, it's a lot simpler to just add 1 oz. of it to my 5 gal. cans when I go to refill them. Can't say I've had any fuel issues since I've started using it for 5-6 years.

I have 5 different David Bradley 2 wheel garden tractors I use in the garden, each with a different cultivator, or attachment. All date back to the very late 40's, the rest through the 50's. A couple have the OEM Briggs engines, the rest have been repowered with either a 3 hp. Briggs, or Tecumseh engine. All use the ethanol laced pump gas with Stabil 360, and a dab of MMO in the engine oil. Got one out 2 weeks ago to mark out rows in the garden for planting a couple early items. Started on the 3rd pull, on last years gas. Can't kick on that. But they are all gravity feed to the carb., not like they have the vacuum fuel pump where the diaphragm gets stiff from ethanol and won't pump fuel.

I do use non ethanol gas in my 2 cycle engines, but still add the Stabil 360. Again, has worked for me for 5-6 years I've been using it.

There are a couple Youtube video's on how to test coils with a digital voltmeter if you've never seen them. EZ-PZ to do. If the airgap is the problem, and index card is the perfect feeler gauge. Loosen the coil, roll the flywheel magnet 90º to the right of TDC. Place index card on top of the magnet, roll back to TDC, and loosen screws holding the coil, letting the magnet pull the coil down against it. Snug screws, and gently roll flywheel back to the right pulling on the index card, and you're done. States it right in a 50's - 60's OEM B&S repair manual if you have one.

 

[DJ54]

I always wanted to try some of them JC Whitney engine rebuild pellets in a can.

Actually, Ajax cleanser works lot quicker and is cheaper. My buddy told the story of their Ag. teacher showing them that trick on a small Briggs engine they were going to tear down and rebuild in shop class. Started the engine up with the air filter off which smoked badly. Picked up a good-sized pinch of Ajax, and let the engine pull it in. Magically, a couple minutes later it quit smoking. That lasted about 5 minutes, then it REALLY started smoking..!!

 

[ROUSTABOUT]

For my purposes, Seafoam works great to keep the fuel system clean. I got that suggestion to use it either here on this small engine forum, or on another tractor forum. I couldn't figure out why my 2 Wheel Horse 310-8's were hard to start in the Spring, then later through the Summer if they sat for a week or so. They would start eventually if you kept cranking them over. I was informed that there is a small check valve ball in the carb that can get sticky and not seat properly, and let fuel drain back to the tank in the rear. Just had to keep cranking until the fuel pump pumped gas back up to the engine. It would start fine if it sat for maybe 3 days, after that, crank until it started.

I was informed to add the Seafoam as directed would cure the problem. Right as rain, it did fix the problem. I still use it every now and then but when Sta-bil came out with the Sta-bil 360, which stabilizes the fuel, plus cleans the fuel system like Seafoam, it's a lot simpler to just add 1 oz. of it to my 5 gal. cans when I go to refill them. Can't say I've had any fuel issues since I've started using it for 5-6 years.

I have 5 different David Bradley 2 wheel garden tractors I use in the garden, each with a different cultivator, or attachment. All date back to the very late 40's, the rest through the 50's. A couple have the OEM Briggs engines, the rest have been repowered with either a 3 hp. Briggs, or Tecumseh engine. All use the ethanol laced pump gas with Stabil 360, and a dab of MMO in the engine oil. Got one out 2 weeks ago to mark out rows in the garden for planting a couple early items. Started on the 3rd pull, on last years gas. Can't kick on that. But they are all gravity feed to the carb., not like they have the vacuum fuel pump where the diaphragm gets stiff from ethanol and won't pump fuel.

I do use non ethanol gas in my 2 cycle engines, but still add the Stabil 360. Again, has worked for me for 5-6 years I've been using it.

There are a couple Youtube video's on how to test coils with a digital voltmeter if you've never seen them. EZ-PZ to do. If the airgap is the problem, and index card is the perfect feeler gauge. Loosen the coil, roll the flywheel magnet 90º to the right of TDC. Place index card on top of the magnet, roll back to TDC, and loosen screws holding the coil, letting the magnet pull the coil down against it. Snug screws, and gently roll flywheel back to the right pulling on the index card, and you're done. States it right in a 50's - 60's OEM B&S repair manual if you have one.

Post cards, index cards, paper that thickness works good.

 

[jbradley]

I finally got it started again, but I'm back where I started as it runs great when cold and runs for about 5 minutes before bogging down. I definitely had the air gap too wide, as I'd used a piece of milk jug at the suggestion of a YouTube video. It measured 0.40mm. I subsequently used some card stock that I had, and it measured 0.22mm. I'd ordered some feeler gauges, so I'll get it to spec when they arrive. I've got a couple of days to play with, now, as we had heavy thunderstorms last night, and it will be too wet to till until it dries up a bit. In the mean time, I also need to also change out the PTO gears, as under a heavy load, such as with with the rotary plow, it jumps out of gear.

 

[jbradley]

After posting above, I found a spec sheet for the gx390 engine, and the 0.40mm piece of milk jug should have been good, as the spec is for 0.40mm or 0.17in.