Roboticinfo

It sounds like you guys don't know deep down about the engine,
You guys are giving simple responses, the engine is made up of alot more parts then you describe. You guys didn't even know what a magneto was until I mentioned it.

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mstechca

I took apart the entire lawnmower.

I think now the only thing that could be causing the problem is the motor circuit. Everything else is fine, and nothing is clogged.

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Roboticinfo

That is not a dc motor circuit!!!!!!!!!!!!!!!!!!, that is a magneto.

Did you check the valves and see if there is any carbon build up.

Did you check the flywheel?

Did you check the connecting rod?

Did you make sure that the piston go's to top dead center?

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bryan1

Hiya mstencha,
You did say before when you cranked the motor there wasn't much compression also you haven't stated if it's a 2 or 4 stroke motor. If it is a 2 stroke have you been putting a bit of oil with the fuel everytime you refill?
If there isn't any compression then you need to overhaul the motor, probably not a bad idea if you have it apart. Buy a new piston ring and hone the bore so there isn't any scratches etc. If you need more help just ask mate.

Cheers Bryan

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Roboticinfo

That would not be the case, a minor problem like that will not make it not start.

Think about it mate

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mstechca

I think mine is a 4-cycle engine. The oil goes in one compartment and the gas goes in another. They are not supposed to be mixed together.

I do get suction when I cover the spark plug hole with my thumb and pull the cord. I also get suction when I cover the carberator top (the part where the air filter is supposed to attach to).

It seems that the pistons are OK.

I oiled the flywheel (or the thing that continuously spins with the blades when the lawnmower runs) with WD-40, and once when I tried starting the engine, a pile of blue smoke went out of the top of the lawnmower.

It seems that if I can obtain the right distance between the U piece and the flywheel (the two parts of the magneto), then maybe it will start. It seems that the farther apart they are, the less chance it has of starting.

What amount of tension should I be feeling when I pull the cord slowly with the brakes off?

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Roboticinfo

Did you put a business card under the magneto?

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pike

you think its a 4 stroke motor ey?

if you remove the exhaust cover and see the combustion chamber itself you have a 2 stroke. you can even see the piston move up and down as you pull the cord. if it's covered by a standalone valve its a 4 stroke.

http://science.howstuffworks.com/two-stroke1.htm

heres a nice place to find more info about engines.

you say it starts for 1/2 a second and then dies yes?? I would think there is a blockage in the fuel line somewhere. It starts on the fuel left in the line (for 1/2 a second) and then dies because of too much fuel resistance. Then it slowly refills the line again because of the low pressure in the line, but too slowly for the engine to operate properly.

blocked carby ??? blocked fuel line??

Edit: magneto info herehttp://home.howstuffworks.com/chainsaw5.htm

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mstechca

Nothing is blocked. I checked every single piece possible. My mower must be a 4-stroke.

and how will a business card help me? because I aint taking this thing to a dealer yet.

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Roboticinfo

A business card will show you if the magento is centered with the crank shaft. If you canot fit a business card under the magneto then it means that it is forcing the crank shaft to move slow which means that it will barley start and then shut down.

If you really knew abou engines then I would believe that you examend everything but since you do not no ways to repair the engine that gives me different thoughts.

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tansis

Check the carberetor , odds are the float chamber is full of water.

As water is more dense than petrol , when you refilled the tank any droplets on the inside would of been displaced to the bottom and been the first thing through the pipe to the carb.
A classic symptom is that the engine will run at tickover but dies when you crack the throttle open.

Another thing to consider ...
just how old is the petrol you used?

storage containers are sealed but the fuel tanks for engines have a breather pipe to the atmosphere to equalise the pressure, last years gas in your mower would have "boiled off" some of , if not all the lighter fractions that make for easy detonation. As a rule of thumb fill a "zippo" type ciggarette lighter with the suspect fuel (observing the makers safety rules) if it wont light then the fuels useless.

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mstechca

I changed both my oil and fuel before I even posted about this subject.

Is it better if I use a piece of paper instead of a business card?

and is the objective just to barely slide the paper or card through the contact points in the magneto circuit?

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Roff

You may be right, but a new spark plug doesn't fix a clogged fuel filter. Seems like Zach's suggestion is worth trying.

Roboticinfo

No use the business card a paper is to thin

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Roboticinfo

Of course it is worth trying, when fixing engines you got to try everything that could be a possibility.

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