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Briggs engine has me ready to shoot it!!!

J

JDseller

Well-known Member
My Grand Daughter is going to college. She and three other girls rent a house. They bought a mid-priced push mower to mow their yard three years ago. She was mowing the yard a few weeks ago and it ran off speed wise. She shut it off before it blew up. She brought it home to me to fix. It would start but just as soon as it got going it would over speed. DID start hard but would start.

I tore into it and found that the plastic air vane/governor had broken. No problem. I ordered a new one. It came in yesterday. I installed it. I cleaned everything up under the flywheel. I then tried to start the mower. No start. I checked for spark. Light yellow. AHHH the problem. I put in a new spark plug and still poor spark. So I put a new coil on it. Now I have bright blue spark. Tried to start it. No go. Removed the carburetor an cleaned it and installed a new kit. No run!!!! I removed the flywheel to check the shear key. All was fine. I checked compression, right up to spec. I even adjusted the valves. I have brought it up on compression and checked to see if it is firing on TDC. It is. Check for intake leaks, all is tight. You can not even get it to hit one time on starting fluid or WD 40. I have had the carb off three times and it looks fine. Still no hit or fire.

The only thing I can find that I question is that the flywheel has the magnet on one side and a counter weight on the other. At least I think it is just a counter weight because it is not magnetized. I marked the one that is magnetized and it is at the coil at TDC. It seems to spark at TDC.

I am at my wits end on this thing. I came close to using the sledge hammer on it today!!! I gave the Grand Daughter my push mower to get her yard done with.

SO where do I go next??? I am out of ideas on this thing. I have asked the two local small engine guys and they could not think of anything I have not tried. So what do you guys think????
 
Is the blade loose or sheared off? The blade acts as a flywheel and if it is not tight to the shaft, it can be very hard to start.
 
if you'll bring yours, il add the pos i have and we can shoot both of them lol never ever, will i own a briggs powered anything again, since they went to china, there just barely better than no engine at all, [ when they do run]
 
This may sound dumb when you have good spark in air, but
have you tried a different plug? They fire differently under compression.
Cheap and easy to try.
 
You didn't say if the spark plug gets wet or stays dry like in not getting gas. Could you have a piece of carb linkage installed wrong?
 
For the time and money you have already invested into this mower...I believe that I would have bought her a new on and scraped that one!
 
JDseller,
I took the head off a briggs that had been over reved. One of the valve seats fell out. Only seen that happen one time. So if you have good compression, I can't see how you have a valve seat problem.

Does it fire if you remove the breather and put a little gas in the carb?

If you have good spark, good compression, a little gas doesn't make it fire, I'm out of ideas other than you need a big gun.

Like to know if you find the problem. I'm never too old to learn.

George
 
That sounds frustrating, lots of good suggestions. I bet if you put some green paint on it you would understand it better! I am having a good night, I bought a big Jonsered chainsaw off craigslist for $15 and had it running within an hour of getting it home. Good thing I flushed out the gas tank, it looked like someone threw up in it!
 
1) The plug will not get wet. So I am pretty sure it is a fuel issue.

2) Tried several spark plugs including one out of a running engine. All will work in running engine.

3) Removed the cylinder head when I adjusted the valves. I also lapped them so the seats are good.

4) The blade does not turn on this mower as it has a blade clutch system on it.

5) The engine will not fire when I spray gas into it with a spray bottle. I could under stand not running with just the carb, but no fire when shotting gas into it. That really blows my mind.

I know I could have bought her a new mower for the time I have spent. She is kind of proud of living on her own. She was up set that "her" mower blew up. It also has become a challenge now. So the fight to the death is on!!! LOL
 
I know that stance!
This doesn't have the electric shutoff on the bottom of the carb bowl being a pusher right?
Diaphragm carb?
No fuel pump, gravity feed to the carb?
Try a (very) little gas in the cylinder?
 
I will just add an experience I had many, many years ago. We sold lawn mowers, before cub cadets, for one year at dealership. I was doing some work on one and when I got done , it would not start. Boss walks by, says you need the blade on it. I said huh, he says put it on and try it . Put it on, started right up. Well, me not really believing this, took it back off and that darn thing would not start.
 
Recently I bought a used Honda, one cylinder engine that did not start. It had plenty of compression but before I messed with it much I took it to George, the air cooled genius. He turned it over with his hand and noted the compression count was off, indicating that a valve was not opening. Next he removed the valve cover and the valve gaps were twice what they should have been. After regapping the valves, engine rotation-compression sequence was normal
 

You didn't make a carb flange gasket and forget to punch out the center hole???
has it got that little primer bulb? What happens if you pump it real good? I have an old mower (B&S) that I have to nurse with the primer bulb til it gets warm
 
i wonder if the cam is damaged, the lobes on these china pos's are a plastic sleve slipped over a metal shaft, the lobes and gear are PLASTIC. so i bet when it over reved it tore it up.
 
Reminds me of one I had that about pulled my arm off. Turns out it would not run with resister type spark plugs....finally tried a non-resister and away it went. Man was I PO'd.
 
You should have taken the sledge to it before you dumped money into it...

Have you taken the plug out and dumped a cap full of gas directly into the cylinder or just shot gas into the carb throat? I've seen strange things where they won't start on ether and won't start for spraying gas in the carb...

Rod
 
Try reading your can of WD 40 .... "NON FLAMMABLE"
Only now a water dispersant. It used to work as a starter fluid with a slight oil base to help seal rings for better compression, but since they took out the Flamable agent will not work for starting engines.

How old of an engine?
does it have a choke or the plunger bulb?
code and serial # would be a + to trouble shoot your problem.

If plug doesn't get wet sure sounds most likely not getting gas.

I would be looking at the throttle shaft for possible worn parts that may lead to "sucking air".
If seems a little sloppy or too much side movement try a Q tip with a little Vaseline or grease around the shaft to seal out possible leaks then see if it gets enough vacuum to pull the fuel in.
 
I believe in trouble shooting, but when I have had an alarm clock start to malfunction, it became my next 50yd, 100yd, or 200yd target. Depending on what you want to shoot next and safe available field of fire, it has earned the right to be your next target!!
 
JDseller, how was the flywheel key. Those are aluminum and are made to shear if the blade hits anything. IN my experience the slightest shear in those keys give them a no spark condition. I cant stress that enough. The slightest little mark in the key where it tried to shear the key will through it out of wack and give no spark. Try a new key if it has a shear mark on it. they are cheap.When i scrap out a mower, i save the keys. Give us a follow up story on what did solve your problem.
 
Cylinder is not getting wet from fuel so gas is not getting into cylinder from carb through the intake tube even after squirting gas into intake. Check the composite (plastic) intake tube for cracks and/or loose at the mounting screws. Is carb flange O-ring in good shape? Other than that I would pull off the crankcase bottom cover and look the cam over for bad compression release, worn out gear teeth and worn out plastic lobes preventing suction of fuel on intake stroke.
 
Personally I'd get a can of REAL starting fluid.

wd40, as somebody mentioned doesn't work - I've also had trouble spraying gas in - you really need it vaporized properly to work well. ESPECIALLY in smaller engines.

Real starting fluid works.

It's a good sanity check. And it sounds like you're at the point of needing one of those.

If it fires on that (and I think it WILL), you can be pretty sure you've got a carb problem. If it doesn't, you can be pretty sure you've got an intake or ingition problem.

Do yourself a favor and go buy a can of it.
 
I like propane. Always some here, it won't wet A plug and I can keep it running as long as I want & much cheaper than starting fluid, plus if backfires, there is no wet starting fluid to keep on burning.
 
I had Briggs like yours. Had spark but would not start or nearly impossible. Auto Light 458 fixed it . Think that was the #. Happened years ago.
 
I would replace the shear key; even though it looks good, even the slightest nearly invisible defect will prevent a Briggs from running. I know from experience.
 
all of em? mine in my pos lawn rider [ the wife's ride, i use the real tractor] has a made in china sticker on it i bought it new in '10 and i didnt put it there ... just wondering now...
 
will that sheer key make a briggs run like the timing is retarded? mine runs [ when it does run] like its firing too close to tdc, and backfires at low rpm also, it acts like it tries to run backwards, i adjusted the valves, which did need it badly, helped, but didnt solve the problem completly dont want to swipe this thread, but talk of that sheer key has me thinking, the wife is one who will run this pos to the ground THEN say honey can you look at this? lol
 
I feel your frustration !! I hate small engines. They seem to be harder to get right then anything. Makes no sense as they are so simple. I think the time and parts costs factor in too. I try to get buy without putting a fortune in them and it just doesn't work out.
 
I think this may be the answer, I purchased a carb kit for a 6.5hp Briggs, installed it and it wouldn't start, I called the dealer I bought it from and he said to compare the mounting gasket to the old one and said to check for the extra hole in the old one, I punched a hole in the new one and it started on the first pull.
 
Had the same frustration many years ago on a Briggs. The one you're working on probably doesn't have points, but I finally ended up widening the points gap a bit to advance the timing and that solved the problem. Jim
 
Did you change the oil. I did on one and used regular 30 wt because the stupid army likes it. Found out you can't use 30 wt it takes 10 W 30 to allow the easy start to work correctly.
Walt.
 
I would take the valve cover off and watch the rocker arms(assuming this is a newer OHV model)...my bet is the intake lobe is wiped out....my rider has a plastic & pressed metal cam....my pusher is all plastic....Rider did the same thing and it wiped out the intake lobe....welded it up & re-ground ran for another month and the exaust side went...welded up & re-ground , and has been fine for 2 yrs now....check the cam :oops:
 
(quoted from post at 07:39:04 08/17/12) I think this may be the answer, I purchased a carb kit for a 6.5hp Briggs, installed it and it wouldn't start, I called the dealer I bought it from and he said to compare the mounting gasket to the old one and said to check for the extra hole in the old one, I punched a hole in the new one and it started on the first pull.
Click to expand...

Sounds good to me...............
 
If none of the suggestions work, pull start it with a30 foot rope on a desreted asphalt road with several utility poles on each side. Jim
 
The shear key will actually make it advanced and if it isnt sheared to bad sometimes it will try and kick back and jerk the rope out of your hands. But mainly a no start condition andor very hard to start.
 
I've got a Briggs that had the exact same problem. Finally figured out that the flywheel/ crank/key had a tiny bit of slop. I mean tiny. But if I held the flywheel in a counterclockwise direction while I tightened the starter clutch it would start and run fine. The looseness in the key area must have affected the timing enough to cause the problem.
 
I went to the Badger Antique Show today. So I did not have time to look at the lawn mower any today. It will be next week at the earliest, that I will have time to work on it anymore. I will let you know how I come out on it.

Thanks for all of the input and ideas.
 
Since you had the blower housing off and replaced the coil, is there any chance you have pinched and shorted the small kill wire to the coil when you re-installed the housing? Worth checking.
 
Since you have compression you must have air entering the cylinder. Do you have air exiting the muffler? I just ran into that with a Honda engine. Great compression but no fire. Without air flowing through the engine you won't have oxygen to support combustion.
 
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