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anyone want to explain this one?

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was doing some prerunning before the baja 1k this past Wednesday and the bike started to sputter like it was out of gas. i coasted off the course and tried kicking but could tell i was losing compression somewhere. pulled the tank and pulled the plug wire with my plug attached looking like this. i have yet to pull the head, but i'm hoping the threads and ground electrode are still intact without any damage to the internals of the engine.

the bike is an 08 kx450f that has been ported with a wiseco 13:1 high compression piston. there is no reason to run race gas at that compression so i've always just ran premium pump gas. but we refilled at mikes sky ranch that morning with what i found out later to be 87 octane. i couldnt hear any pinging in the engine bc the sound of the wind going by drowns out the sound of the motor so i dont know if it was pre-detonating. has anyone seen this happen before or know what might have caused it? i had just done a 5th gear whoops section and the bike died right as i was done with them so it could've been a lot worse.

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I have seen this happen many times on cars. Like has been said earlier, most likely fatigue from a possible number of reasons, we can get to that latter.

You could possible remove the rest of it without removing the head. Put an easy out in it just the correct size and grind off what you don't need to make sure you don't push the ground electrode into the engine.

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how long was that plug in there? Metal fatigue most likely...not gas.
the plug only had a few rides on it. everything was torqued down to spec.
Looks like it was loose, I see dirt all around where the crush ring sits.

i noticed that too. i think it was dropped in the dirt while getting passed around for the other riders to look at.

i'll pull the head tomorrow and hopefully find no damage and the rest of the plug still intact in the head where it should be.

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Looks like the plug was put in dry and it seized in the head, snapping off at the base. Not the first time I have seen it. It did not happen because of the fuel.

+1

Or the plug was over torqued when it was installed.

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I had this happen on a 125 once. The head gasket started leaking coolant into the cylinder. Coolant burns very hot so the plug got overheated. The side electrode and threads melted down and fell into the engine destroying it. When I pulled the plug wire it came out with the insulator just like yours. Mine had droplets of water so you could tell it was sucking coolant. Hope your engine is OK.

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I had this happen on a 125 once. The head gasket started leaking coolant into the cylinder. Coolant burns very hot so the plug got overheated. The side electrode and threads melted down and fell into the engine destroying it. When I pulled the plug wire it came out with the insulator just like yours. Mine had droplets of water so you could tell it was sucking coolant. Hope your engine is OK.

after reading this, i had to go check my coolant and its still full. so thats a relief. this top end is only 8 hrs old. it should barely be broke in.

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Well, maybe burning the glycol is not the exact correct description of what is occurring, but when you blow a head gasket and coolant and water get in the combustion chamber you will have a decreased coolant level in the coolant system and you will have white smoke coming out the exhaust. Where did the coolant go and what happened to it?

Oh, and ya might wanna read this.

http://www.firefighterclosecalls.com/news/fullstory/newsid/99811

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If you had antifreeze going into the motor,you would have whats called a "flash cool".But that would destroy the insulator,not what you are experiencing.

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I have seen this happen before, and like others have said, an easy out popped them right out.

Chalked it up to poor quality plugs (in almost all cases, Champion) and that was that.

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Glycol burns????? I don't think so.

Alcohol based coolant does. A buddy of Loose and I blew a head gasket on his RM 250 2t a couple of years ago at the Mtn. The bike would start and run fine until it got hot, then the rpm's would take off to the point where it was going to come apart...apparently all from the coolant it was burning.

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Since when is 13:1 not high enough to need to run race gas, or at least something a hell of a lot higher than 87?

the bike is an 08 kx450f that has been ported with a wiseco 13:1 high compression piston. there is no reason to run race gas at that compression

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Since when is 13:1 not high enough to need to run race gas, or at least something a hell of a lot higher than 87?

you can run race gas at that compression but you're not benefiting anything but running a cooler bike. they filled the gas cans at a Pemex down in mexico that didnt have premium. i didnt fill the cans so i wasnt aware that it was only 87 octane until it was too late. the bike ran fine up until it blew the plug. i could tell i was missing some power with the crappy gas but it got the job done. i'll chalk it up to an over torqued plug and not the bad gas.

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If your going to pull the head off you will know for sure if the fuel was causing a problem. If you know someone with a bore scope you could remove the rest of the plug and take a look at the piston and combustion chamber without removing the head.

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