What does this mean?

[Dr. Mordo]

http://austin.craigslist.org/mcy/1321732442.html

It sucked a spark plug into a cylinder?

[Bear]

:shock: Must of been painful, My head hurts just thinking how that might of happened.

[jsingraham]

Hmmmm, never heard that one before.  I have however witnessed a plug being shot our into a freshly harvested cornfield.  happend to me once about 15 years ago on my old 200X 3-wheeler...found it after about 30 minutes of searching, and it had gone about 20 yards off of the trail I was on.  I had recently cleaned the plug, a few days prior to riding, and I guess I just hand threaded it in and forgot to put a wrench on it.  Then a couple days later after 30 minutes or so of riding, it started running like crap and pop, it was gone!

I have never heard of an engine sucking one in, and honestly can't figure out how that would happen.  Would have to have had some valve issues too in order to create suction enough to suck the plug in I would think, but still can't see that happening.

[Stretch]

I've had a plug (Autolite) come apart once... the threaded steel shank remained in the head (VW GTi) while the ceramic insulator was spat out of it.

I'll move this to 'Speaking of Bikes', since it's not Steamer-related.

[Dr. Mordo]

I had a plug shoot out of a Ryder truck I rented.  The pressure an engine generates is huge; that's how it works.  But that pressure comes from the explosion of the gas/air mixture.  There is nowhere close to an equivalent amount of vacuum in an engine.

But I just don't see how a plug can be drawn thru the threaded hold and into the engine.  How much vacuum would that take?  I'm guessing an impossibly large amount.

I should probly just email the dude and ask.

[c-rad]

Wouldn't the vacuum "force" be limited by atmospheric pressure in this instance?  Even if the cylinder were totally evacuated, it seems like the most pressure available for pushing the spark plug in would be 14.7 psi.

Sounds funny to me too.

[Bixxer Bob]

Wouldn't the vacuum "force" be limited by atmospheric pressure in this instance?  Even if the cylinder were totally evacuated, it seems like the most pressure available for pushing the spark plug in would be 14.7 psi.

Sounds funny to me too.

Aha!! The scientific approach!!!

Agreed.  And the pressure inside pushing out is many times greater than any pressure outside pushing in (not that there is much of a vacuum in there at any time, as the intake stroke that would make a vacuum is pulling mixture in through the inlet valve at the time).  

Either he got very unlucky and the tip of the plug detached on him (never heard of that happening but an outside chance that the piston could wack it if the wrong - longer - plug were fitted), or he means he's dropped a valve.  Either way it's expensive - more if you can't do it oyurself.  

At least a bore hone, if not a rebore - and then you have to do all three so it's a cost balance against resleeving one bore plus one piston against boring all three plus thee pistons.  Then there's  probably a couple of new valves and some time dressing any damage out of the combustion chamber in the head.  Then there's oil, gaskets, etc etc  Am I boring anyone yet....

[Dr. Mordo]

Yep, you guys are making sense.  

I was thinking that it was likely a valve problem.  But part of me wonders if it's something completely else that might actually be easier to fix.  The sucked in spark plug kinda sounds like a load of crap from a mechanic who didn't know what was wrong with it.

[Sin_Tiger]

Maybe he is just using the term "sucked" in a very metaphorical sense  :shock:

Some plug electrodes are made up of multiple components, with resistances to reduce RF emmisions, iridium tips are one example, the whole electrode length is not iridium. Trust me I split one up years ago that came out of my Renault Turbo just out of curiosity and I could see two fused "joins" along the length. So it may be that he has been unlucky enough to have had a substandard one, or very bad combustion on that cylinder that caused breakdown within the combustion chamber.

It's all supossition as it seems everybody has come to the same conclusion, expensive rebuild, but might still be worth it if the rest of the bike is up to scratch as they seem to be going for a bit over $3,000.