Spark plug unscrewing itself?

[fireburns99]

I just got back from a dune trip, and i had a problem with the spark plug unscrewing itself. It would unscrew itself about halfway out, and then foul itself when i lost compression. It would only do it sporadically, and i even changed spark plugs and it still did it. I don't think it could hurt the top end by coming out a little but i'm not sure. The only thing that i can think of is that the threads on the head are bad. Has anyone had anything like this happen to them? I'm just curious if i need to pull the head off, and the topend apart.

[zedicus00]

this is usually caused by detonation. its possible that it did some damage to the topend. its also hard on the rod and bearings.

[fireburns99]

The only thing that doesn't make sense is that it has never done that before, and i used the same gas and same mix ratio. Would the summer blend of gas effect the way it burns and possibly cause detonation? The only difference is that i put on a sparks pipe. Would that make a difference?

So maybe i will pull the topend apart, to be on the safe side, thank you for the help zedicus.

[GPracer2500]

Be careful running a head that is having trouble holding a plug. A loose plug won't effectively transfer it's heat into the head. If the plug gets too hot you might pre-ignite. Usually the first sign you'll have that pre-ingiton has taken place is the hole in the middle of your piston. :eek2:

I had a buddy have a plug come loose on his 250r. It burned the side electrode of the plug right off. Luckly it didn't appear to do any engine damage. Although now that I think about it, that engine only ran a few more hours before the piston let go.

[zedicus00]

that new pipe may have had better flow, making the engine run a bit leaner/hotter. check the top end and then richen up yur jetting and see if that helps.... maybe even add a lil octane boost in the gas tank, if that helps then you should just switch to race gas, octaine boost is NOT anything more then a temporary fix....at best.

[fireburns99]

yea i agree i was thinking that the pipe may have made the engine run a little hotter. Also i think my radiator cap is bad because its letting coolant drip out of the overflow. That could be another reason. I did richen up the jetting, i went from a 178 main with my fmf, to a 182 with the sparks pipe. Maybe it was a combination of the radiator cap and the pipe. Either way i think that i may just rebuild to be safe.

I'm still running a stock carb so maybe that will help to.

[novaracr70]

i may b stupid but how does a plug come loose without it either being stripped? or not tight enuf? a loose plug hase nothing to do with jetting , pipe or anything like that

[GPracer2500]

Originally posted by novaracr70
i may b stupid but how does a plug come loose without it either being stripped? or not tight enuf? a loose plug hase nothing to do with jetting , pipe or anything like that

Well if your stupid I'm stupid too because I was wondering the same thing.

I've never once heard of loose plugs being a symptom of incorrect jetting or overheating. I'm not saying the jetting is right, I'm just saying I don't see how that has anything to do with a loose plug.

:confused:

[fireburns99]

it has to be do to something, because it just started. I've never had a problem with a plug unscrewing itself either. I even tried 3 different plugs. And we're question jetting/etc because it could be detonation that would cause a plug to unscrew. I'm looking at any possibility. I already acknowledged that something could be wrong with the the head. I'm open to any ideas.

[zedicus00]

its a symtom of detonation. detonation can be caused by an engine running hot, low octane, and other things.... then again it may just be stripped, or not tite to begin with....

i seen a guy thread lock a spark plug in that was doing this, ran great, till the piston grenaded.

[GPracer2500]

Originally posted by zedicus00
its a symtom of detonation...

Gotcha.