Help smashed or melted spark plugs

[BMH]

I have just recently got a new to me KX 500 1990 fresh rebuild top and bottom by a shop. I put a new oem head gasket on. The problem is... I was out for my first long ride and thought i fouled a plug so i took it out BR8EG (new)and the gap was smashed into the electrode the color is fine. I put in my spare and 10 miles later the same thing happened. I wont claim to be a genius mechanic but I took the the extra crush washer off the first plug and doubled up washers put it back in and made it home from BFE it ran a little weird not quite as responsive it was jetted perfect before. I pulled the 2nd BR8eg after getting back alot of high speed sandwash and it looks kind of melted? The original plug was a NGK B8ES.
 I am running the jetting on the great chart from this site with the moose reed spacer. I was doing alot of really tight single track first gear both times it happened. I dont think there smashed just melted. I am running 91 octane at 32 to one with red line pre-mix. any help would be appreciated. (jetting 162 main 58 pilot 2nd notch needle.)

[GDubb]

I've never seen anything like that and it doesnt make any sense... if you are hot enough to melt plugs it seems you would be overheating like crazy or burning a hole in the piston.

[BMH]

I am at a loss but not for power (so no hole in piston) I didnt overheat no loss of coolant it was a cool morning 60's, the first plug i pulled i didnt look at too close I was trying to hurrry and catch my buddy. I was riding a gear high trying to get some hook up, lugging it a bit thats why I thought I fouled the plug. The rest of the ride I stayed on the pipe thats when plug 2 melted down. The stranger part was after i replaced plug 2 with the 2 washers I ran flat out in sand washes for 20 plus minutes and got home I pulled that plug and it was fried.

[BDI]

I would start by making sure your carb is clean with no pluged jets. Then I would follow that up with a leak down test. Doing a leak down test is easy and you can make your own leak down tester for cheap If you are interested I will explain how to do It. I wonder if it could be caused by a ignition timing problem .

    P.S. Don't take the engine apart before you do a leak down or you may never know what the problem is.

[medicman]

I would be intrested in the leak down tester

[BMH]

I would like to know how to do a leak down test

[KXcam22]

BMH,
  That is an interresting problem.  I have seen similar to that before but long time ago and can't recall the specifics.  I doubt that it is piston mechanical damage.  I run the BPR8ES, the "P" projected nose plug.  It is longer and there is still lots of room.  If you recall the shape of the head, the chamber makes it is impossible for the piston to hit the plug without huge damage.  I remember now:  I broke a piece of piston skirt off and it made it through the transfer port and was bouncing around on top of the piston, hence every so often it would bean the plug and close the gap.  I suggest that you take off the exhaust pipe and have a quick peak at the cylinder/piston to inspect for possible damage.  One thing that is nice about a 500 is that you can do a pretty good internal inspection by shining a light down the plug hole and looking up the exhaust port.   On another topic, it is possible to overheat so fast that the coolant won't boil over.  I once had a CR500 CDI go south.  Was breaking it in at the time, all conditions perfect, but it would seize every few minutes.  Took 7 seizes to get back to the truck.  I was stumped until I noticed later that night that I had no spark.  Hope this helps. Cam.

[Hillclimb#42]

 That's probably it Cam, maybe a broken ring during break in. Its a pain to stick the piston in the jug and hold the rings where they are supposed to be, especially if you do it alone. Something is in there. You might as well pull off the top, because no matter what it is, it has to come out. The head has a domed combustion chamber, like cam already pointed out, so the plug would never hit the piston.
  Whats the leak down test going to show on new motor? If it leaks off compression, wouldn't it still need a visual inspection and repair?  If it doesn't lose any, wouldn't you guys still have to pull off the top end to fix it, no matter what is causing it? Seems like that test would only confirm there's a problem, when that's obvious. What would that test tell BMH about the cause?

[hughes]

BDI is concerned due to the guy saying the plug looked melted. Pressure testing the engine is great way to check main crank seals, crank case halves, intake boot etc. to ensure the engine is not sucking air from another source.

[KXcam22]

Just for some similar info.  I once assembled a snowmobile engine but got the timing way off. Ran fine but burnt a hole through the piston in about 15 minutes. It can happen fast. Its hard to tell from the photo it the plug is melted or mechanically bent. Cam.

[Hillclimb#42]

I see. Looking for a lean condition. Super lean condition. Plug wouldn't be white or green? Hmmm, timing. Easy to check that. Is there any way its melting plugs? Its designed to be in the combustion chamber all the time. I melted a piston and rings ( brand new ) in a super lean-out deal, plug was fine. Now I'm interested to hear what it is.
  Let's hear how to make a home-made leak down tester then, BDI.

[BDI]

This is the spark plug out of the bike I'm working on right now. It's not a very good picture but if you look close you will see the gap is closed. The second picture is of the the piston that almost has a hole clear through it. The cause of this was the fact that the oil injection line came off of the intake and let air in. This caused a lean condition that caused the engine to start detonating. The lean condition made the spark plug so hot the electrode became soft and then the detonation did the mechanical work of closing the gap.

  When an engine has a failer you have to treat it like a crime scene. You have to start collecting evidence to find the culprit. Leak down testing is one very helpfull crime fighting tool. If you do not figure out why the engine failed it is very possible you will rebuild the engine only to have it blow up again. When your engine blows up because of a bad main seal and you stick $500.00 into a new top end only to have it melt down again you will then see the importance of leak down testing.

[kaw rider]

you can build a tester for under $30.00

[maddoggy]

This is the spark plug out of the bike I'm working on right now. It's not a very good picture but if you look close you will see the gap is closed. The second picture is of the the piston that almost has a hole clear through it. The cause of this was the fact that the oil injection line came off of the intake and let air in. This caused a lean condition that caused the engine to start detonating. The lean condition made the spark plug so hot the electrode became soft and then the detonation did the mechanical work of closing the gap.

  When an engine has a failer you have to treat it like a crime scene. You have to start collecting evidence to find the culprit. Leak down testing is one very helpfull crime fighting tool. If you do not figure out why the engine failed it is very possible you will rebuild the engine only to have it blow up again. When your engine blows up because of a bad main seal and you stick $500.00 into a new top end only to have it melt down again you will then see the importance of leak down testing.

well said bdi, once again you are right on the money. chech out the cause thouroughly before you end up wasting a few hundred bucks doing a repair only to have the same thing happen again.  MADDOGGY

[Hillclimb#42]

Good info BDI. Two thumbs up.