# Ariens 520 spark plug screw up



## angus (Feb 14, 2016)

Hello,
i recently discovered that i put in the wrong spark plug in my snow blower and it was too long. it smashed the bottom of the spark plug. i took it out and put the old one back in but now it wont start at all. I was wondering if i may have knocked the time out of whack. any thoughts or ideas on this would be greatly appreciated.

thanks.


----------



## Grunt (Nov 11, 2013)

:welcome: to SBF angus. There is a possibility that you sheared the flywheel key and it has changed the timing. When you pull the starter rope, do you feel resistance from the engine compression? Hoping you didn't bend a valve or put a hole through the piston if this a 2-cycle motor. Have you tested for spark at the plug? Posting the engine numbers will help with further advice.


----------



## Kiss4aFrog (Nov 3, 2013)

:welcome: to the forum angus


----------



## skutflut (Oct 16, 2015)

I'm kind of guessing its a flat head and you put a long OHV style plug in there.

With the correct plug installed, is there any compression when you pull the engine over? 

Take out the spark plug and pull the motor over and see if you can see the piston coming up to the top. It will be hard to see, but check if there is a hole in it.

You should probably remove the cylinder head and check for any bits of spark plug insulator or other bits of junk that may have broken off the plug. Also check the valve seats to make sure nothing is jammed in them, and that nothing is left inside the intake and exhaust ports.

Try and compress the valves to see if they come out straight and close fully. Best bet is remove them to check for sure.

If the piston has a hole in it, you will have to replace it, the rings, and possibly the connecting rod which may have taken a nasty hit if the piston is broken.

Flywheel key might have sheared, but it you didnt actually get the engine started, and the piston hit the plug tip, then there would not have been that much inertia present and you might be ok with the flywheel key. That said, as long as you are checking things out, you might as well check everything out.


----------



## angus (Feb 14, 2016)

thanks everyone . i will check all that out today and post my findings k:


----------



## Blackfin (Jan 25, 2016)

If it's an L-head Tec my guess is the longer plug came into contact with a valve head and when you turned it over the valve was bent.

Good luck.


----------



## RedOctobyr (Mar 2, 2014)

skutflut said:


> I'm kind of guessing its a flat head and you put a long OHV style plug in there.


Indeed, this shows that it's a 5hp 195cc Tecumseh flat-head (L-head): 
Ariens 520 Consumer Two-Stage 20" 5-HP Snow Blower Recoil Start



> With the correct plug installed, is there any compression when you pull the engine over?


This seems like perhaps the simplest test/question, to better understand the problem. 

Does the pull-start feel "normal", vs before the incident? Or is it significantly easier to pull than it usually is? If it has suddenly gotten much easier to pull, and doesn't provide the normal bursts of resistance (due to the compression stroke), then maybe you punched a hole in the piston, or got something stuck in a valve, etc. Something that is reducing/eliminating your compression. 

If you don't have compression, you can at least pull the plug and check if the piston is still moving. If you can't see the piston through the hole, you can stick something like a long (!) pencil down the hole, assuming the plug hole is located above the piston, not the valves. Hold onto the pencil gently (you don't want it to drop down inside the hole!), and slowly pull the cord, and see if the pencil moves up/down with the piston. 

As this is a flat head engine, removing the cylinder head is easy. That would let you look at all this stuff directly. 

If the pull-start feels like it has normal resistance, and therefore normal compression (or especially if you also pulled the cylinder head and everything looked normal), then perhaps you did shear the flywheel key. 

You may be able to check the flywheel key by removing the shroud around the flywheel, and looking down through the flywheel nut. You may be able to see the groove in the crankshaft, which the key sits in, and also the groove in the flywheel. If those grooves are not lined up together, the odds are good that the flywheel key sheared. You would have to remove the flywheel to replace the key. This needs to be done properly to avoid damaging the engine, do some reading before trying to take it off, if it came to that.


----------



## Vermont007 (Mar 29, 2015)

If you "smashed" the Spark Plug, were you able to get the shards of broken porcelain out of the cylinder before trying to start it with a different shorter plug ?


----------

