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Started By
Message
Small engine lawnmower help (update:fixed)
Posted on 6/12/22 at 8:45 pm
Posted on 6/12/22 at 8:45 pm
Mower is probably 6-7 years old. Briggs & Stratton/ Toro. I rebuilt the carburetor 2 years ago and put new spark plug and air filter at that time when I had trouble starting it.
Was working flawlessly a few weeks ago, first pull everytime. This week won’t start.
I have a spark
I took the entire carburetor down and flushed every port
It won’t even sputter or act like it wants to turn over. Only response I get is an occasional misfire when I’m cranking it.
Any thoughts?
Was working flawlessly a few weeks ago, first pull everytime. This week won’t start.
I have a spark
I took the entire carburetor down and flushed every port
It won’t even sputter or act like it wants to turn over. Only response I get is an occasional misfire when I’m cranking it.
Any thoughts?
This post was edited on 6/15/22 at 5:21 pm
7
Posted on 6/12/22 at 10:45 pm to Knuckle Checker
When I saw that you have spark AND you flushed the carb, you undercut my first two ideas 
Shots in the dark:
What about compression? Is the compression good?
Going back to air & fuel: Is the air filter excessively clogged?
What about the muffler? Sometimes the screen gets clogged.
Fuel line? The carb might be clean, but is gas actually getting TO the carb in the first place?
Shots in the dark:
What about compression? Is the compression good?
Going back to air & fuel: Is the air filter excessively clogged?
What about the muffler? Sometimes the screen gets clogged.
Fuel line? The carb might be clean, but is gas actually getting TO the carb in the first place?
Posted on 6/12/22 at 10:48 pm to Knuckle Checker
See if it runs when you spray a little starting fluid into the carb…if it runs, your problem is with the fuel lines or the carburetor.
Posted on 6/12/22 at 10:58 pm to Contender54
quote:
What about compression? Is the compression good?
Haven’t check that, but good idea
quote:
Is the air filter excessively clogged? What about the muffler? Sometimes the screen gets clogged.
Filter and muffler are pristine
quote:
Fuel line? The carb might be clean, but is gas actually getting TO the carb in the first place?
Definitely fuel in the carburetor, it comes pouring out every time I remove it.
This post was edited on 6/12/22 at 11:00 pm
Posted on 6/12/22 at 10:59 pm to Spankum
quote:
See if it runs when you spray a little starting fluid into the carb
Tried that and it doesn’t even sputter a bit. Just an occasional backfire pop
Posted on 6/13/22 at 5:29 am to Knuckle Checker
May be out of time. Check flywheel key.
Posted on 6/13/22 at 7:23 am to Knuckle Checker
quote:
Any thoughts?
I'm only asking this because I've done this before...is there fuel in the tank?
Posted on 6/13/22 at 11:37 am to Knuckle Checker
did you hit anything with it or have a good backfire happen? sometimes the crankshaft key will get sheared off and that throws the spark timing off and then it wont run
pull the nut off of flywheel and see if the slot on the flywheel and crank are still in alignment. the occasional misfire sounds like the key sheared, you can get them at any hardware store
quickest easy way to test for a fuel issue is spray a shot of starter fluid and if it wont start, then you know its not a fuel related issue
pull the nut off of flywheel and see if the slot on the flywheel and crank are still in alignment. the occasional misfire sounds like the key sheared, you can get them at any hardware store
quickest easy way to test for a fuel issue is spray a shot of starter fluid and if it wont start, then you know its not a fuel related issue
This post was edited on 6/13/22 at 11:53 am
Posted on 6/13/22 at 2:02 pm to Knuckle Checker
Could very well be a safety switch issue. Shouldn't be more than a "dead-man" switch. That is the bar you hold that kills the mower when you release it.
It'll likely be very simple. Follow the cable and be certain it isn't broken and is pulling the switch enough to activate. You can usually manually manipulate the lever on the switch.
It'll likely be very simple. Follow the cable and be certain it isn't broken and is pulling the switch enough to activate. You can usually manually manipulate the lever on the switch.
Posted on 6/13/22 at 2:14 pm to Knuckle Checker
quote:
I took the entire carburetor down and flushed every port
Including the jet? Sometimes I flush everything and still had to run a welding torch tip cleaner up it to make sure it's open...damn ethanol...and damn sta-bil for saying it works...
Posted on 6/13/22 at 6:56 pm to keakar
quote:
pull the nut off of flywheel and see if the slot on the flywheel and crank are still in alignment. the occasional misfire sounds like the key sheared, you can get them at any hardware store
I’m going to do this but I got to the flywheel and I don’t have a socket large enough and you can’t get an adjustable wrench in there.
The safety switch is good.
I think the best possibility at this point is a sheared flywheel key but I didn’t hit anything and it was running great until I put it up last time. So that doesn’t make much sense.
Posted on 6/13/22 at 9:06 pm to Knuckle Checker
I don't see any mention of checking and cleaning the spark plug.
Another thing to try is take the air filter off and see if it will start.
I have a B & S engine that requires pulling the starting rope 15 or 20 times to get it to start. OR.... I can put a little gas in the air filter and it starts on first pull.
Another thing to try is take the air filter off and see if it will start.
I have a B & S engine that requires pulling the starting rope 15 or 20 times to get it to start. OR.... I can put a little gas in the air filter and it starts on first pull.
Posted on 6/14/22 at 12:14 am to gerald65
quote:
I don't see any mention of checking and cleaning the spark plug.
Spark plug is good
quote:
Another thing to try is take the air filter off and see if it will start. I have a B & S engine that requires pulling the starting rope 15 or 20 times to get it to start. OR.... I can put a little gas in the air filter and it starts on first pull.
No improvement with air filter off or starter fluid sprayed into carb
Posted on 6/14/22 at 3:42 pm to Knuckle Checker
Had a similar issue with an old generator. Make sure the rocker arm on the intake valve and push rod is in place.
Posted on 6/15/22 at 5:23 pm to Ldogg123
Fixed it
Figured out I didn’t have any compression. So I took the head off and the exhaust valve wasn’t closing all the way. It was remaining open by probably 2 millimeters. I sprayed some penetrating oil behind the valve and gave it 2 taps with a hammer. It slipped right back into place. Put everything back and it’s humming after the first pull.
Makes me wonder how many lawnmowers are sitting out for the trash that are such easy fixes.
Figured out I didn’t have any compression. So I took the head off and the exhaust valve wasn’t closing all the way. It was remaining open by probably 2 millimeters. I sprayed some penetrating oil behind the valve and gave it 2 taps with a hammer. It slipped right back into place. Put everything back and it’s humming after the first pull.
Makes me wonder how many lawnmowers are sitting out for the trash that are such easy fixes.
Posted on 6/16/22 at 5:42 am to Knuckle Checker
Thanks for updating this. Why was the valve not fully closed? Bent valve? Carbon between valve and seat? Broken spring? Stem to guide clearance out of spec?
Has to be a reason and if not found, it may happen again.
Has to be a reason and if not found, it may happen again.
Posted on 6/16/22 at 7:47 am to jake wade
Sometimes the valve seat can slip out of place as well
This post was edited on 6/16/22 at 7:48 am
Posted on 6/16/22 at 7:50 am to jake wade
quote:
Thanks for updating this. Why was the valve not fully closed?
I wish I knew
I’m assuming it was some carbon build up around the valve stem because the penetrating oil seemed to break it up and it would spin easier and then I tapped it back into place.
It wasn’t bent, there wasn’t significant carbon between the valve and seat, and the spring was in good shape
I heard someone on YouTube saying that you should let off of the start engine handle slowly when you want to stop the engine. He said that if you just suddenly release the handle it can cause the engine to stop with the valves open.
So I’m going to try to slowly kill it from now on. And run some sea foam through it.
Posted on 6/16/22 at 12:47 pm to Knuckle Checker
quote:
I heard someone on YouTube saying that you should let off of the start engine handle slowly when you want to stop the engine. He said that if you just suddenly release the handle it can cause the engine to stop with the valves open.
The valves are open or closed based on mechanical timing. A sudden or slow shutting off of the engine isn't going to change that.
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