Starts, Runs fast, Then dies in 30sec

I have a Lawnboy mower of which I'm not sure the model. It does however say "Solid state 21" on the side, maybe that is the model name. I purchased it used in 2010 and have no idea how old it is.

I've often had problems with finicky starting, but now I have a bizarre problem. This morning I went out to start it, with my usual routine thats always worked. Press primer button 5 times while tipping lawnmower about 60 degrees to right side until I can hear fuel squirt. Pull string and start. Often it will start on the first pull this way.

Again it did today. However despite the throttle being set to "light" the engine raced off to what sounded even faster than what it does at full throttle. Switching the throttle between "light" and "normal" had no effect. I thought it might be stuck and kind of jiggled the mower up and down tapping the wheels on the ground. The engine then dropped down to what sounded like its usual "light" speed then slowed to a stop in less than a minute. Nothing I could do would get it to restart or so much as a pop of ignition.

I pulled the plug, cleaned it. Checked air filter, pulled whatever I could out of that. No change. So I took apart the carburetor, cleaned every bit of it with carb cleaner, inspected it. I don't see anything obviously wrong. Re-assembled it all.

I went through my usual starting routine and... It started! For awhile. It ran full speed again then 15 seconds after starting the engine again slowed to a stop and nothing I could do afterwards could make so much as a single combustion event.

I'm at a loss here. Any ideas before I have to borrow the neighbor's mower? :biggrin:

I don't know if this is related but I have never been able to start this machine while hot, not that it really was hot in this case. When I do my lawn I have to make dam sure I got everywhere because if I turn it off there is no hope in a restart for 30 min afterward.

Here are some pics of it if it helps at all. I don't see a model number on it.




EDIT: Eliminating variables

I did the ol' spark in the dark test and it looks like plenty of spark.
Checked float and confirmed it floats, and seems to float with plenty of pressure to close valve.
The only thing that I see is adjustable is the mixture screw. I tried adjusting that in a few positions and starting again. This time after re-assembling I can't get any action at all. Also compression feels the same as it ever has by "through the string" feel.

If I had to guess I'd say your governer is sticking try reaching under and and moving the governer link if its stuck, try looking to see if its possible that its jammed weird against the throttle if not your speed adjustment may have hung up on the wire that it is connected too

This governor business is a little new to me. If I'm understanding you, the link is that part that sticks up from the throttle control into the slot in the housing above? I wasn't sure what that was for. I thought it seemed like an empty space in the slot above but didn't look close. What exactly should a proper connection in that space look like?

And after my second round of getting intimate with this mower I sill don't see a model number anywhere. Perhaps there was once an information plate attached to it or something.

if you look under the right side of the plastic housing you should see a small silver sticker on looks to me like d 300 but cant be sure your local shop should be able to work with that number to give you the model the governer is usually a bent linkage that runs from the throttle lever to a plate under the flywheel this plate is hooked to a little setup that when the engine revs centrpigul force makes the little round metal peices spread out that in turn due to being hooked up to a round piece that directly connected to the governer plate makes it move up and down pushing on the throttle linkage the little speed control lever will be hooked to the top plate of the block and will have a little protusion with a bend going up under a piece of wire thats bent in a u shape that is also connected to the governer plate by moving this lever back and forth it moves the bent piece back and forth the bent portion then while moving is setting directly under the little u making it move up and down and controlling the raising and lowering limit of the governer plate thus by controlling your speed. sounds like the speed lever has slipped out of the little u wire or is kind of jammed. Hope this helps

I have yet to tear into this mower again today. However after doing more poking around the net it would seem I have an "airvane" type governor. It sort of looks like a paddle that sticks up from the carburetor. I'm reading conflicting methods on how your supposed to adjust it. This is all pretty disheartening before I start as I don't see how governing could prevent a mower to even start in the first place.

Secondly I can't seem to figure where the fuel adjustment screw should be turned to when trying to first start again.

And 3rd I can't see why a non functioning Governor would cause the engine to slow to a stop as if it had just run out of fuel.

Almost sounds like I've had multiple problems all spring up at the same time.

Ah ha. Found my model number. It is a F-100... and no closer to running. :confused2: I borrowed the nice old lady next door's mower for today and mowed her front yard (and my own of course) and returned it full of gas in exchange. I'll have time this weekend to dig into my own mower.

Check out this thread. It is a service manual.

http://www.scribd.com/doc/26622228/Lawn-Boy-Service-Manual-1950-88-Complete

Check out this page of links to LB manuals (free):

LAWN-BOY SERVICE MANUAL 1950-88

Take a look at the sections relating to "F-series" fuel system troubleshooting.

A problem with the governor can cause the engine to be hard, if not impossible, to start -- if it's stuck in the wrong position.

Thanks, those manuals are helpful. One thing I noticed right away looking at the manual is that my carb is altogether missing the butterfly. I don't know if this just fell on the ground without my noticing when I disassembled it or if it wasn't in there to begin with. It always ran fine until yesterday and can't imagine that would happen if that butterfly was always missing. I'll need to inspect my shed floor carefully tomorrow.

I did think it strange seeing no butterfly in the carb. I just assumed the slit in the vertical shaft was what increased or decreased fuel flow depending which way it was turned. :laughing: