Ok, I purchased a new lawn mower about 2 months ago.
I chose it because I had heard good reports about this model.

Anyway, about 2 weeks ago, I tried starting it, it wouldn't fire, and after the basic checks it appeared that the engine wasn't getting compression, as the spark plug had worked its way loose.
I re-torqued it and it fired.

Next time I went to start it - same thing. I immediately checked the spark plug. I removed it, and it appears that its spark plug didn't have any gap... (sorry about the poor picture quality)
Confused as I had never seen the ground wire bent right around onto the centre wire. I replaced the plug.
The motor fired fine.

2 days ago, I went to start it again - wouldn't fire again...
Checked the spark plug immediately. Same thing (ground wire bent around onto the centre wire).
I replaced the plug again. Now even after replacing the plug with a brand new plug, it STILL won't fire.
Absolutely stumped, I go over all of the rest of the basics - all are fine.

The engine spins over fine when the cord is pulled, but it will not fire.
Fuel is probably about a month old (but it is very clean).
First oil change done about a week ago.
Done about 10-15hrs work.
Air filter is clean.

I'll be honest I am completely lost - What could be wrong with it?
Any assistance would be greatly appreciated.

 

is it possible they put the wrong plug in it???

 

Originally I assume?

I don't think so, is a possibility, but I do know both the replacement plugs I put in are DEFINATELY the correct plug.

 

Sounds like something made its way into the motor and hitting the electrode.

 

That looks like the spark plug was too long. If you're sure it wasn't, something is in the combution chamber that shouldn't be.

I'd probably pull the head off. Assuming it's not OHV (doesn't look to be) this is pretty simple. Just make sure you remember which screws came from which holes, because they aren't always the same length.

 

loose plug, closed gap. common small enigne failure. the connecting rod or piston has broken

 

Thanks guys, I shall pull it apart and see what carnage unfolds.

 

Ok guys,

I pulled the head off, and unfortunately there wasn't any foreign material in the combustion chamber, and the piston looked fine - I didn't take the sump off, so I couldn't tell if the con rod had an issue, but the piston was running up and down the chamber fine when I rotated the crank.

Now, when you say "the spark plug was too long" - what specifically do you mean?
The new spark plug appears to have the same length as the old one, and the spark plug is specifically for Briggs and Stratton 2-11hp

 

Check to make sure you have spark still. Sometimes, the briggs engines will rust a little when they sit, right on the magneto. If there isn't any spark, or it's really weak, pull the coil assembly off and clean the curved face with 400 grit sandpaper. Use a piece of thick paper (good inkjet paper works nicely) between the flywheel and coil to set the gap. Bolt the coil down tight, touching the paper. The first time you spin the engine over, it will spit the paper out. If it still doesn't have spark, put everything back together and see if the warranty is still good.

 

definitly check for spark

as far as the plug being "too long" make sure the length of the threads is is the same as the original, but the prob sounds like youre not getting spark

 

I think what the others mean when they say the plug is "too long" is that the electrode and ground are sticking too far into the combustion chamber.

I have a few ideas for you that haven't come up yet.

It sounds like you already got someone to look up the plug to make sure it was right, so I'll scratch that one off my list and move on down the line. Did any of those plugs happen to have a crush gasket on it? A crush gasket is usually a little ring of metal that goes between the plug and the cylinder head. It sort of looks like a washer, but you can't use a regular washer to replace it. I think those plugs are supposed to have one. It will be made of a relatively soft metal. If you still have the spark plug box, you might check to see if it is in there. Sometimes they don't put them on for you. The tapered edge is the one that should be pressing against the cylinder head.

If you don't have one, the plug might go into the head a little bit too far. In addition to that, it is possible that it might vibrate loose without it. I've seen it happen, anyway.

Otherwise, if you've got that head off, I'd check to make sure that the threads where the plug screws in look good. If they're stripped out, it might not have enough threads to properly hold the plug in there.

 

Ok, will grab some sandpaper when I am down at the store later today.

If that doesn't work, I shall reassemble and return it (its got a 2yr warranty) - just thought I might have been able to fix it (and learn some stuff in the process)

All of the plugs have/had a crush gasket.

I have reassembled the head - the thread on the plug screw looked fine.

 

Will it not start because the plug gap keeps getting knocked shut, or is it something else?

If it is the plug closing up, why don't you put two crush washers on the plug to keep the tip away from the piston. This way you can use it until the rod breaks, then you can take it back for warranty.

Just be sure to keep plenty of oil in it. They will check to see if you put oil to fill it up after it broke or not. Oil added after a breakdown is always nice and clean.

Don't take too much apart. Rounded off bolts from operator repair really throws up a red flag when warranty time comes around.

Lots of times the problem with customers equipment I worked on was what I called M-O-T-O, (malfunction of the operator).

 

Will it not start because the plug gap keeps getting knocked shut, or is it something else?
Originally I thought so - but this spark plug appears fine...

 

That motor should have a champion J19 or J17 or ngk B2lm or B4lm spark plug in it what do you have or had in it when it was crushed.