Crushed Spark Plug, WTF?

[Arthur Kill]

**Twilight Zone Music***

Toro 4-stroke, 87CC OHV Electric Start taking off a 18-inch snowthrower. Pull start is locked - pull the spark plug and it's CRUSHED, like the piston slammed into it. (Yes, I checked, it's the correct spark plug.)

Pull the starter cover off and I can spin the fly-wheel a little more than 180 both ways before the engine locks up. And get this, the piston moves freely up-and-down while I move the fly-wheel!

Had good intentions for this engine on a very small mini-bike for little kids - I'm wondering what could be causing this? My first thought was a broken connecting rod but I can't see a reason why the piston would come back down if it was that?

Any help or theory is appreciated.

Thanks!

 

[Steve73]

**Twilight Zone Music***

Toro 4-stroke, 87CC OHV Electric Start taking off a 18-inch snowthrower. Pull start is locked - pull the spark plug and it's CRUSHED, like the piston slammed into it. (Yes, I checked, it's the correct spark plug.)

Pull the starter cover off and I can spin the fly-wheel a little more than 180 both ways before the engine locks up. And get this, the piston moves freely up-and-down while I move the fly-wheel!

Had good intentions for this engine on a very small mini-bike for little kids - I'm wondering what could be causing this? My first thought was a broken connecting rod but I can't see a reason why the piston would come back down if it was that?

Any help or theory is appreciated.

Thanks!

A story this good comes without pics?

 

[Strigoi]

Sounds like it's time to open the engine up and see what's going on.

Did it run fine before and this just happened?

 

[SAS289]

Engine would have to be opened to fix it anyway. No need to guess what it is.

 

[Arthur Kill]

A story this good comes without pics?

I know, I know. But the only pic I considered was the crushed spark plug, which isn't very exciting. Maybe I could get my wife to hold it in a bikini?

 

[Arthur Kill]

Sounds like it's time to open the engine up and see what's going on.

Did it run fine before and this just happened?

It is. I wanted to survey the more experienced here because this engine has very little value unless it runs. Any investment in time and/or parts would surpass the engine's actual cash value.

Got it from a friend who only reported that "he could not pull the rope." but i will ask him how it got to this condition.

Thanks!

 

[ole4]

Sounds like rod broke piston hit head

 

[Arthur Kill]

Sounds like rod broke piston hit head

Pretty sure it's not that.

The piston goes up AND down when I turn the flywheel, so....

 

[ole4]

could it be the wrong length plug? Does it turn over completely if you remove the plug?

 

[Rapidrob]

Head gasket missing?

 

[Mariah]

Sounds like something got dropped in the spark plug hole. Screw, nut, check ball?

 

[Arthur Kill]

Sounds like something got dropped in the spark plug hole. Screw, nut, check ball?

Yes, I think you're right, the most logical explanation is that something is in there - but the more I ponder it, the more I think not "dropped in", but broke. I'm thinking likely a broken valve?

You think?

 

[Mariah]

look in the plug hole or pull the head and you will know.

 

[Arthur Kill]

Yep, OHV valve related.

Pulled off the OHV cover and right away noticed the valve spring just laying there. The valve was nowhere to be found, so the whole thing is probably down in the cylinder, busting apart. The rocker arm was broken and pieces of it were laying out, also the push-rod was laying askew.

Not sure what the nexus was? What happened first? There's no fixing this as the parts diagram doesn't even list the parts as being available. They're just greyed out (see below).

Thanks to all for your insight, I really appreciate it!

 

[Davis]

The valve should be under there.

 

[Arthur Kill]

The valve should be under there.

By "under there" you mean, dropped down into the cylinder, right?

 

[Davis]

Under the head.

 

[Strigoi]

There's no fixing this as the parts diagram doesn't even list the parts as being available. They're just greyed out (see below).

Now you have an excuse to buy fun parts for it and make a bunch more power. That is providing the cylinder bore isn't f'd from the carnage that happened. A new piston is cheap and a mild head isn't too expensive. Couple that with the billet parts and a small cam and you'll be good to go. Also need a header and a carb setup too then. It's only money.

If the engine is salvageable, ask around on here. People may have stock parts laying around they don't want/need after doing upgrades.

 

[65ShelbyClone]

I'd bet that there's some major carnage if you pull the cylinder head. Dropping a valve usually means serious damage to the piston and head when it's bad enough to mangle the spark plug.

 

[noseoil]

I had a piston ding the spark plug once, but that was at 8500 rpm with a modded motor & a very heavy piston (Bullfrog hemi predator piston at 11:1). Tore it down, a few new parts & it's back up & running again. I stay away from 8500 rpm now & don't go above 8000 with this motor.

Yep, tear into it & see what's inside!