lawn mower techs?

[BuzzStPoint]

Been having issues with my lawn push mower.
Last year it would start fine and normal. 1-2 pulls. I would only run for a minute or two then the RPMs would slowly decrease till it killed. Then it would be 5+ minutes of pulling and repeat. After 2-3 times like that it would run fine.

This year i couldn't even get it started. So I changed plug, cleaned carb, changed bowl gasket, needle and seat. Got it started, but it does the same thing. When I finally get it running to where it will stay, it seems very low on power. Any thick grass will severely bog the engine down.

Any ideas?

Tecomseh engine
LV156XA 331010A
Carburator is a : Tecumseh 640339

Work performed so far this week.
New Plug
Changed oil - Synthentic
Removed and cleaned carb
Needle, seat, bowl gasket replaced.
Sharpened and balanced blade.
Re gapped the pickup to flywheel.

 

[i386]

Re: lawn mower techs?

Not a lawmnmower tech but couldn't resist...

I noticed you didn't mention checking the air filter or compression. Fuel, fire, compression...

 

[paultjohnson]

Re: lawn mower techs?

Had 2 issues with my lawn boy. Kinda the same symptoms. One time the little spring had become disconnected at the carb, I think its from the governer .. .. Same summer the choke butterfly had become disconnected from the cable.. Look down by the carb, i bet sumtns' disconnected or amiss

 

[rbh]

Re: lawn mower techs?

Air leak at carb, starts fine cold and choked, then not?

 

[Bob_VT]

Re: lawn mower techs?

Probably the largest culprit is the carb.

Even though I took careful care of my small push mower....... I ended up rebuilding the carb again last week and it's running like a champ again.

It really does not take but a tiny bit of crap to mess up the motor...... IF you have a primer button....examine it for cracks too.

 

[BuzzStPoint]

Re: lawn mower techs?

Not a lawmnmower tech but couldn't resist...

I noticed you didn't mention checking the air filter or compression. Fuel, fire, compression...

Those were all checked when I wouldn't start.
Air filter is new when I changed the oil, plug and carb kit.

Compression is running 58-60 PSI

Springs and govenor linkage is set right. Thought I'm not sure the spring tension is right. Don't know why the tension would be tighter then new on a spring. When the motor starts to die I can seen the govenor move the throttle closed but then it dies out.

There is a primer bulb looked at that. Seems normal. but you would think if it had cracks it would leak fuel when sitting.

 

[scipper77]

Re: lawn mower techs?

Stalling when heated up could be ignition, General lack of power could be head gasket (lack of compression). I'm not saying that these are the problems but it sounds like you have addressed the fuel system. Assuming this is a flat head motor the head gasket should be pretty simple to replace (If it needs it).

You could also try loosening the fuel cap while running to see if that is the issue (It's a free check).

 

[windy5849]

Re: lawn mower techs?

Here is a link to the rebuilding info for your carb(series 11).Could be the gas cap,but I think you need to clean the passages in the idle restrictor and the bowl nut(high speed jet) to cure the problem.If it was stored with unstabilized fuel,there could be some gum in the jets.Hope this helps.

http://outdoorpowerinfo.com/repairs/tecumseh_series_11.asp

Here is the link to your engine manual.You may have a weak or broken governor spring?

http://www.barrettsmallengine.com/manual/tecumsehlheadmanual.pdf

 

[dolluper]

Re: lawn mower techs?

Did you clean the bowl nut passageway...if not use a copper strand from piece of wire to clean ....float set right? or spring on float pin missing ....they sometimes fly when float is removed
check this link might give you more insight ....<<Oopps wrong carb link above is right same principal
http://outdoorpowerinfo.com/repairs/tecumseh_carb_640342.asp

 

[waterinthefuel]

Re: lawn mower techs?

You need to take some of this advice with a grain of salt.

If it does as you describe, it is a carb issue. Not sure what, but it is a carb issue. No ignition problem will cause it to slowly die. It will either run, or miss so bad it will die like that, but a slow reduction in throttle is only capable of being caused by a fuel problem. I'm a licensed aircraft mechanic and this is what I would suspect with a plane running the same way. While an airplane engine and lawnmower engine are different, all carb'ed engines run on the same principles. That's why, once you learn how to work on one type of carb'ed engine, you've got 90% of them down pat. I've had my outboard do the same thing when I forgot to open the vent on the tank.

It's obviously a fuel delivery problem as an engine will run on whatever fuel its getting. What is causing this slow cutoff of fuel? Could be a fuel pump or something, not really sure. It's starving for gas (or air), that's obvious. Does it have a fuel pump or is it gravity fed? Sounds like one piece of advice on here was good, might be that the fuel tank isn't venting correctly. I wish you could try another fuel cap. You could take that cap off, put a piece of cellophane wrap around the neck of the tank and put a rubber band on it just to run it long enough to see if that helps. Punch a couple of small holes in the cellophane and try to run it. If it runs good, its your tank vent, ie. fuel cap. If it still messes up, your fuel cap is probably fine.

Bugs and dirt can get into vented fuel caps and plug them up. It would make sense if it wasn't venting that it would run briefly and stop. Then you change a bunch of stuff, TAKE OFF THE FUEL CAP AND CHECK THE FUEL, (thus introducing more air into the tank) and then try it again. It will run until the air is gone out of the tank and then it will starve for fuel and die.

My vote is something to do with the fuel tank venting. After that, it would be something is wrong with the carb.

 

[rbh]

Re: lawn mower techs?

Our has had this issue in the past, how I found out I had an air leak was to spray WD-40 around the mating area
(carb-head)

What happens is when the engines cold and you start with the choke on your good, but as the engine warms up and everything expands you get an air leak, the wd-40 will be sucked into the leaking area and you will here the engines RPMs pick up.

Hope this helps, but as others have said could be other issues.

 

[scipper77]

Re: lawn mower techs?

Stalling when heated up could be ignition, General lack of power could be head gasket (lack of compression). I'm not saying that these are the problems but it sounds like you have addressed the fuel system. Assuming this is a flat head motor the head gasket should be pretty simple to replace (If it needs it).

You could also try loosening the fuel cap while running to see if that is the issue (It's a free check).

You need to take some of this advice with a grain of salt.

If it does as you describe, it is a carb issue. Not sure what, but it is a carb issue. No ignition problem will cause it to slowly die. It will either run, or miss so bad it will die like that, but a slow reduction in throttle is only capable of being caused by a fuel problem. I'm a licensed aircraft mechanic and this is what I would suspect with a plane running the same way. While an airplane engine and lawnmower engine are different, all carb'ed engines run on the same principles. That's why, once you learn how to work on one type of carb'ed engine, you've got 90% of them down pat. I've had my outboard do the same thing when I forgot to open the vent on the tank.

It's obviously a fuel delivery problem as an engine will run on whatever fuel its getting. What is causing this slow cutoff of fuel? Could be a fuel pump or something, not really sure. It's starving for gas (or air), that's obvious. Does it have a fuel pump or is it gravity fed? Sounds like one piece of advice on here was good, might be that the fuel tank isn't venting correctly. I wish you could try another fuel cap. You could take that cap off, put a piece of cellophane wrap around the neck of the tank and put a rubber band on it just to run it long enough to see if that helps. Punch a couple of small holes in the cellophane and try to run it. If it runs good, its your tank vent, ie. fuel cap. If it still messes up, your fuel cap is probably fine.

Bugs and dirt can get into vented fuel caps and plug them up. It would make sense if it wasn't venting that it would run briefly and stop. Then you change a bunch of stuff, TAKE OFF THE FUEL CAP AND CHECK THE FUEL, (thus introducing more air into the tank) and then try it again. It will run until the air is gone out of the tank and then it will starve for fuel and die.

My vote is something to do with the fuel tank venting. After that, it would be something is wrong with the carb.

Agreed, the advice I gave may be pointed in the wrong direction so let me digress....

The O.P. claims that he can get it to run now but it is lacking power, this could very well be a head gasket. My snow blower is acts just like this because it has a bad head gasket. Many small engines are designed so that when you pull start them they will not see full compression making a traditional compression check useless. The reason this is done is because it would be to hard to pull start the motor if it could make full compression.

I've heard that ignition coils can fail in such a way that they are fine when cold but as they heat up they fail. I really don't have any experience with ignition systems in small engines like this so I should have probably kept that one to myself (sorry!, waterinthefuel, thank you for keeping me honest, I feel bad if I am sending someone in the wrong direction)

The gas cap thing is just a basic no brainer thing to me. Even though it's likely not the issue here, it's so simple that I just couldn't see not checking that first.

I hope you find the root of your problem, make sure to update this thread if you do solve the issue, we are all learning with you here.

 

[BuzzStPoint]

Re: lawn mower techs?

I'm starting to think it may be the head gasket.
I fired it up and it did the same thing.

loosened the gas cap and even pulled out the rubber vent and cleaned everything in the cap. Same thing. Yesterday I pulled the carb apart again, and ran wires through every passage I could get too with no other result. Sprayed wd over the carb when running and no change..

I'm sort of leaning toward head gasket, because after a few cycles of starting and letting it die, It will start and and stay running. Wondering if the heat isn't building up compression.
Think I'll run down to the small engine shop and pick one up.

 

[scipper77]

Re: lawn mower techs?

I'm not convinced from your description that it's a head gasket.

If it was the head gasket you might find that starting it is difficult due to the lack of compression. If it is a flat head engine where all you have to do is remove the head and replace the gasket then I'd say go ahead and replace the head gasket. For my snow blower it's a $7 gasket. If it's an over head valve engine then it's a little bit more involved to swap out the head gasket. In that case I would feel bad steering you in that direction because we are not sure that's the issue.

Look all around the head gasket. If it is bad you will see where the leak is. On mine it's behind a heat shield and there is a mark on the shield like someone has been holding a torch up to it.

Another speculation I will throw out there would be a blocked muffler?? Please take my advice with a grain of salt. I could throw out any number of problems and because you are unsure of what is going on you might end up spinning your wheels in the wrong place. I'm just trying to help brainstorm possibilities. It is pretty hard for me to diagnose what's really happening from my computer.

 

[dolluper]

Re: lawn mower techs?

When you rebuilt the carb did you replace the main nozzle [inmulsion] tube o-rings and check tube sprayed freely[carb cleaner}...no cracks in tube...tecumseh's can have a problem with the tube...aftermarket replacements.....they are very finicy the float has to be set right diffently.....idle jet passage clean...there is an outside chance the coil

 

[john3931]

Re: lawn mower techs?

Also check the flywheel key to see if it is sheared slightly. I have had that do some very weird things to mowers.

 

[BuzzStPoint]

Re: lawn mower techs?

Already thought of thy flywheel key.. Looks good and tight. No warping or rounding of the key.

As for the inmulsion tube, I only took it out and cleaned it. Slid it back in.

 

[dolluper]

Re: lawn mower techs?

Humm the old o-rings could br leaking

 

[tx1961whaler]

Re: lawn mower techs?

Hmmmmm.
http://www.harborfreight.com/engine...d-for-all-states-except-california-68123.html

 

[BuzzStPoint]

Re: lawn mower techs?

Kinda silly when I bought the whole mower for about 100 bucks.

Before I buy another mower I'd buy a rebuild kit for the motor.