B&S 550 EX stopped - won't restart

B

BobbyC777

Member
My 2013 Troy Bilt 21" push mower has been running well. But recently after running for about 2 minutes it stalled. It restarted twice but ran for only about 20 seconds - did this twice. I assumed carburetor problem even though I run ethanol-free gas. I took carb off, did normal cleaning, replaced but no luck. It would not even attempt to start even using starter fluid. Here are some steps that I have taken:
  • verified that I have spark by grounding plug to block and using recoil starter
  • replaced spark plug with B&S product
  • replaced coil twice - one cheapy and one B&S OEM 84005272 (properly oriented up/down)
  • undid kill wire from coil
  • set armature gap to 0.012"
  • verified that flywheel magnets are strong
  • verified that flywheel keyway looks good but have not removed flywheel yet
  • compression feels good. Checked with gauge. Get 60 PSI on first pull, goes to 70 PSI on 2nd and 110 PSI cranking it for a few seconds with electric drill.
  • removed carb (again) and shot starter fluid directly into intake port - no luck
  • removed valve cover and verified proper action of rockers/pushrods
    • have not checked valve lash other than to verify that some clearance at TDC
On the surface I have spark (at least outside the combustion chamber), fuel (starter fluid) and compression but it doesn't fire at all.

A couple of additional data points:
  • after sitting for a few hours, the first pull sounds like it gets maybe one minor combustion but it could be my imagination. Subsequent pulls yield nothing.
  • I have spent hours on this and twice it did start with starter fluid and ran for 4-5 seconds (sounded normal). Both times the carb was not even on the machine! But this was only twice out of 100+ pulls.
Fortunately I was able to borrow someone's extra old flathead machine so at least I can keep the lawn mowed.

I have not had any blade impacts. But I have a gut feel that somehow either the ignition timing is off or that the valve timing has changed,
As stated above, I have yet to remove flywheel or check valve clearance. Short of those 2 things I am out of ideas. I would not know how to verify that valve timing had gone bad.
Strange that it fired & ran twice on starter fluid with carb off but only twice out of many, many attempts.

All suggestions appreciated!

Bob
 
Last edited:
Hello B.,

Sounds like you got water or grass clipping in the fuel tank somewhere along the way.

Pull the upper cover and remove the fuel tank and empty the fuel into a clear glass jar to check for water separation or debris. Then blow low pressure air back into the fuel hose nipple to clear it out.

I find this happen on a regular basis because the fuel and tank are the last thing people consider to be an issue. Never assume the "new" fuel in your gas can is "sterile" of water or debris. Check your fuel can well for trash or water floating around in the bottom.

Don't forget to pull the carburetor bowl off and empty it, that way you return everything to a dry condition before adding fuel.

Getting clean fuel these days is becoming a challenge in some parts of the country.
 
BobbyC777 said:
Thanks for the response. But shouldn't starter fluid have made it run consistently for a few seconds?
Click to expand...
Starter fluid is not always reliable due to a high flash evaporation point. Chemtool B-12 carb spray is more consistent when it comes to test firing an engine over like this.
 
@Auto Doc's | Interesting about the Chemtool B-12 Carb spray. You've got me thinking about my fuel as I believe I just got new gas prior to the problem onset. But that same fuel is running my borrowed mower just fine. But maybe water (heavier than gas) got to bottom of my tank.
 
The borrowed mower likely has the old pulse jet carburetor, and they could literally pull a little water in with the fuel and still run.

Your mower is strictly gravity from the tank to the carb.
 
Just drain the tank and carb bowl. Only holds about a quart max if full. Not like you are dumping out a fuel tank on a container ship. Fresh non Ethanol 87 octane gas if you can get it.
 
@Auto Doc's | The borrowed mower has a B&S 158cc flathead from year 2000 with a Pulsa-Prime carb with priming bulb. I will start over with new fuel and empty the float again. This may take me a day or two but I will keep everyone posted.

If it won't fire on Berryman's B-12 Carb Cleaner (I have yet to buy) is there any point in trying new gas?

BTW, I tried starting it again a while ago after it had been sitting for a week or so. That first pull really sounds like it fires once or twice. Then nothing. What's that about?

Forgot to mention that I disconnected kill wire from coil during my testing.

Thanks !
 
slomo said:
Bought from where specifically? Scamazon or Fleabay?

Best to buy plugs from a local auto parts store.

Sounds a little fat to me. If that is what your engine spec is then so be it. I would regap at 0.006" and test it.
Click to expand...
I bought the new B&S plug from local True Value. The new coil came from B&S.
The specs for this engine say armature gap should be 0.006 - 0.014
 
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