Lawn mower starting problem

I'm trying to help my daughter with her lawn mower (Sears, Craftsman). In
the past I've always been able to start them by spraying gas onto the air
filter. This time no luck. I have spark. The ignition is electronic. The
manual says that one of the possibilities is a loose blade. I have the
blade off the machine.
How would the engine know, or care, that the blade is loose or off?
Any ideas?
Thanks, Ivan Vegvary
Reply to
Ivan Vegvary
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It acts as a flywheel.
Reply to
Richard J Kinch
Richard (and your manual) are correct. The crankshaft will not have enough momentum to get through the cycles and actually start running without the blade firmly attached. And you'll feel the difference when you 'pull it through'.
The other problem is you "spraying gas onto the air filter". Not only is this a fire hazard, but it will also score the cylinder wall (sooner or later). Definitely not good for your equipment.
Reply to
reader
Uh, because the blade is the flywheel on a mower engine yidiot :). JR Dweller in the cellar
Ivan Vegvary wrote:
Reply to
JR North
Why is fuel vapor from the filter any different than from the normal carbueration?
Reply to
Richard J Kinch
I used the propane trickling into the carb trick the other day, getting my lawn mower fired up for the summer season. Worked just hunky dory
Gunner
That's easy.... you're too dull witted to be capable of surprise. What little synaptic ability you do possess is stretched to the limit with life support. If you diverted power to the critical thought processors you'd asphyxiate in a matter of minutes.
George Orwell
Reply to
Gunner
If it doesn't fire with propane the spark might be weak and not fire under pressure. Try 1/2 the gap, on the plug as an experiment.
Reply to
Nick Hull
Nonsense. If that were the case things like roto-tillers, go-karts, edgers, and other things that start with 0 load wouldn't start.
Reply to
Gary H
They are fitted with heavier flywheels for that reason. A rotary mower doesn't need that heavy a flywheel as the blade acts as one.
Gary H wrote:
Reply to
David Billington
Once you have the blade back on if the carb has a foam air filter that requires oiling you might make sure its oiled. When they dry out they can allow the engine to run lean and be more difficult to start.
Ivan Vegvary wrote:
Reply to
David Billington
I'll bet you've got an exhaust valve stuck open. Has it been sitting all winter and this is the first start? If the valve's stuck open, take the head off and hit the stem with a little oil, tap it back down and turn the engine through until it starts opening a closing normally. Hope this helps.
Reply to
gfulton
Make sure that the gas is brand new. Even if she ran the mower until it was dry at the end of last season, there can still be old gas in the carburetor bowl. If draining the tank and then putting in new gas doesn't work, take the carburetor bowl off, drain it, clean it, put it back on, and then try it again. You won't need to take the carburetor off. Remove the plug to see if you have carbon between the electrodes. This carbon can build up to the point where the gap disappears completely. If you have a gap, though, you should be okay. Clean the air filter. As a last resort, you can use starting fluid _conservatively_, and understand that this might do more harm than good, if you have not done everything else possible first. If all else fails, move to Austin, and go into the music business. Just kidding.
Mike Mandaville
Reply to
MikeMandaville
Check the key under the flywheel. They a usually made of aluminum and designed to shear. Even if the key is only slightly deformed, it can throw of the timing.
Reply to
Chief McGee
Gary-take a look at the flywheels in vertical shaft rotary mowers and in horizontal shaft motors. You will see an aluminum flywheel in the rotary mower motor and a cast iron one in the horizontal one. And another eye opener is to try to start that rotary mower without the blade. Oftentimes what happens is that the motor, lacking enough flywheel mass, will start to rotate backwards when it fires. When this happens the handle will be torn from your hand instantly. DAMHITK. ERS
Reply to
Eric R Snow
AND if you have a real good grip on said handle you will be in pain for a considerable time!
Ken.
Reply to
Ken Davey
Thanks everybody!!!!!
Put the blade back on and the mower started on the first pull. As recited by other posters, YES, without the blade the rope DOES get ripped out of your hand and worse.
Thanks again. This is the best group for saving my bacon.
Ivan Vegvary
Reply to
Ivan Vegvary
DAMN, no video?
Reply to
Tom Gardner
Maybe there is some truth to what you say but when I was a kid my dad and I would make go karts with normal lawn mower engines (used a fan belt with a 90 deg twist) and they started just fine with no flywheel at all.
Reply to
Gary H
I meant no flywheel other than the one on top. But I am not saying I don't believe you. If I recall correctly I did have to pull the heck out of the rope to get it going.
Reply to
Gary H
There is allot of truth to it. Maybe not all, but most lawnmower engines need the blade attached to act as a flywheel. It is damned hard to even pull some of them over without a blade as the engine will kick back. Greg
Reply to
Greg O

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