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Ive been having this issue for a while now and cleaning out the carburator and doing the carb repair kit thing didn't help. Spark plugs and filter have also been replaced. The issue is when I first crank it after a 4 push prime, the mower will start only to quit about 1 minut later. This scenario will repeat itself about 4 to 5 times. Afterwards it seems to run fine except when I start mowing longer grass and it starts to bog down and quit. I think I may have to bring it in for repairs but not sure if just buying a new mower would be a better idea unless someone here can help me troubleshoot the issue. Would love to have this thing working like new without having to pay too much.

Update: I redid the carb cleaning and still the same issues. Also tried without the gas cap on to see if the cap vents were clogged up and still stalling. Only thing I can think of now is maybe the coil needs to be replaced. Anything else I may be missing ?

First a note about the people who post in this LB forum: with no exceptions that I can think of, we're interested in the two-cycle Lawn-Boy mowers that are no longer made. That's why your post sat unanswered for quite a while -- you have a newer, four-cycle LB. :ashamed:

Based on what you posted, I'd guess it's not the coil (which I assume is solid-state since it's new). Those coils tend to be all-or-nothing so if it runs at all the coil is probably OK. The first thing I'd check is for any crud anywhere in the fuel system (tank, fuel line, filter).

But I have no experience with that engine... so I could be wrong.

Good luck. :thumbsup:

tell me in detail your carb cleaning procedure and I may have a a tip or two.I have did three of them this year with the same issue.

Go to troubleshooting section and see if this helps. http://www.tecumsehpower.com/CustomerService/BSI.pdf


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beg said:

tell me in detail your carb cleaning procedure and I may have a a tip or two.I have did three of them this year with the same issue.

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Well I removed the carb and totally disassembled it. Removed float and pin, removed the small tapered end brass screw that has a small vertical hole and a larger horizontal one. Removed the center plastic red tube with both o-rings and replaced them. Float pin seal was replaced last year so I just cleaned it and put it back in. Removed one of the metal caps that was easily removable. The other one I left alone since I couldn't remove it without damaging it.

All parts were sprayed with carb cleaner and all holes were thoroughly picked through with different sized wire mesh. Also the float bowl screw with both its holes was cleaned.

Reassembled the float and made sure it was horizontal. Tested to see if the float pin seals correctly by blowing air through the fuel intake with my mouth and it seems to work properly. I then reassembled the whole thing and reinstalled it on engine.

I also remove fuel tank and flushed it, cleaned it out and reinstalled it and put in fresh 87 octane unleaded gas.

I also checked the flywheel key for shear and that seemed OK.

Only things left to do that I can think of are governor issues and compression but those last 2 possibilities are more difficult to troubleshoot since it involves taking the engine apart or having compression testing tools.

So after all this I started her up and she ran for 30 seconds before quiting. Restarted her up a few more times until she was able to keep on running. I cut some grass and noticed that engine will quit if more power is needed such as when I'm cutting longer grass. The blade was also replaced so that can't be at fault.

on the side of the carb there is 2 rods that go to a bar attached to the engine.check that the bar is tight I think it takes a torx bit.It is hard to see if the butterfly on the carb is fluttering but that may be your issue.I am not sure where the bar is located on your mower.some are in front of the carb and some are behind it.it sounds like your governor is not working and may be due to incorrect installation of the rods or weak tension on the spring.please note I am not a pro at this but fixed two this year with the same issue

Here's a small video I made of the issue I'm having.

I don't think low compression is causing this problem. It could be a little low but that's not causing the engine to cut off like this. (I watched the video.)

My hunch is that there is a fuel clogging issue. I know you've worked hard to get it clean but maybe you've missed something. Do you know where the fuel filter is located? Some older Lawn-Boys have a fuel filter built into the fuel cutoff valve on the bottom of the tank. If the fuel filter hasn't been replaced or cleaned, try that.

If you like green mowers with the Lawn-Boy brand, maybe you're ready to find one of the older two-stroke models and spend your time on that -- it's a much worthier project -- you'll have a collectible piece that can last decades and increase in value.

Two-Stroke said:

I don't think low compression is causing this problem. It could be a little low but that's not causing the engine to cut off like this. (I watched the video.)

My hunch is that there is a fuel clogging issue. I know you've worked hard to get it clean but maybe you've missed something. Do you know where the fuel filter is located? Some older Lawn-Boys have a fuel filter built into the fuel cutoff valve on the bottom of the tank. If the fuel filter hasn't been replaced or cleaned, try that.

If you like green mowers with the Lawn-Boy brand, maybe you're ready to find one of the older two-stroke models and spend your time on that -- it's a much worthier project -- you'll have a collectible piece that can last decades and increase in value.

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Hmmm...I would be surprised if it was a fuel clogging issue since it does end up running continuously after it quits 3 or 4 times. If there was a fuel clogging issue, the problem would never go away.

Right now Im thinking its either a leak somewhere maybe even the head gasket because as the engine heats up and expands, the leaks are closed up some and thats why engine ends up running continuously. I still have issues under heavy load though such as longer grass areas where I need to tilt the mower up a bit so it doesn't stall. I think the govenor has the job of insuring that I always get enough power under different loads but for whatever reason it may not be working correctly.

OK a small update here. I read up on the governor and it would seem that mine works as intended. You can see it in action in the video where as the engine slows down the governor rod pushes on the throttle body plate and opens up which should give the engine more fuel hence more rpm but it stalls instead.

The only explanation I can think of is that either I need to replace head gasket and fuel intake gasket due to leaks or the carburator is still at fault and although I've cleaned it numerous times maybe I will just replace it.

Why are you asking these questions on two different threads? Are you trying to pit different people against each other?

Rivets said:

Why are you asking these questions on two different threads? Are you trying to pit different people against each other?

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Lol no. It's just that I started off on the lawn boy forum and wasn't getting any replies and noticed there was a forum for tecumseh engines and thought maybe I'd get more replies there. Then I got a reply on the lawn boy forums saying that that forum was for old 2 cycle engines only so since then I've been trying to keep both threads updated.

If there's a competition among responders then Rivets should win -- hands down -- he's a professional and I'm a hobbyist. :laughing:

You should read his post in the other forum carefully. He's given some detailed info about cleaning the carb.

I still think the most likely cause is some kind of clogging in the fuel system. Is there a fuel filter... and if so, have you eliminated that as a cause?

I don't have any real data to back this up but I'd bet that the symptoms you describe are overwhelmingly caused by fuel system clogging -- and things like low compression and a leaky manifold gasket would be way down the list. If you had 1000 of these engines with these symptoms, I'd bet that over 900 have fuel system clogging of some sort.

The degree of clogging could be sensitive to heat so it could vary as the engine gets hot.

Again, good luck.

Tomorrow I'm gonna go buy a compression tester along with a tube of gasket maker.

Initially my problem looked like a fuel issue like some have mentioned here but after giving it more thought I think if fuel flow was an issue then it would always be one. Not just for the first 3 or 4 pulls. Fuel flow seems to be just fine after that as the engine does not quit unless it's being bogged down by a heavier load such as in longer grass areas which I think can also be caused by poor compression.

So tomorrow if I get insufficient pr駸ure readings I will start by changing valve cover gasket and fuel intake gasket. Once that's out of the way and If I still have poor psi readings then this will tell me that it's either the valves, piston rings or both.

Now if psi readings are initially good then the other thing I could try is testing the coil with a spark tester to see if it's giving me good sparks on a regular basis....but honestly...I don't think the coil is bad. These solid state coils either work or they don't.

My wife keeps telling me to just buy a new mower and be done with it but at this point this little problem of mine has become some sort of challenge and I won't be happy till I've solved it

Two-Stroke said:

If there's a competition among responders then Rivets should win -- hands down -- he's a professional and I'm a hobbyist. :laughing:

You should read his post in the other forum carefully. He's given some detailed info about cleaning the carb.

I still think the most likely cause is some kind of clogging in the fuel system. Is there a fuel filter... and if so, have you eliminated that as a cause?

I don't have any real data to back this up but I'd bet that the symptoms you describe are overwhelmingly caused by fuel system clogging -- and things like low compression and a leaky manifold gasket would be way down the list. If you had 1000 of these engines with these symptoms, I'd bet that over 900 have fuel system clogging of some sort.

The degree of clogging could be sensitive to heat so it could vary as the engine gets hot.

Again, good luck.

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Thanks. I've done everything I could think of in regards to fuel flow other than just replacing the carb. Taken the carb apart several times and cleaned and recleaned everything. Made sure float was at the correct height. Made sure all holes were clean.

Wait there is one last thing I could try. Fuel filter is in the tank and I don't have access to it so I could try to swap the tank with another container and connect the hose on that and see if that fixes it. Another Avenue I just thought about is the impulse breather that connects to the upper portion of the carb. I read that this hose sends air into the carb at impulse and keeps the bowl full of fuel. I've tested it by unplugging it from the carb and you can definitely feel the impulses air coming out but maybe there's not enough pressure....or the hose is worn out and the carb isn't getting a strong enough impulsion but then again the same question comes back to haunt me and that's why does the engine not stall after 3 or 4 runs...