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Stihl 362 spark plug blow out

Started by Rhodemont, January 23, 2022, 08:20:03 AM

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Rhodemont

The spark plug in my 362 blew out yesterday.  Saw is about 10 years old and been a work horse.  Started stalling when I let off the throttle last week.  Cleaned the air filter and fresh  fuel yesterday.  Started right up and ran well for a while then started stalling again.  Started back up got cutting and heard a pop and she was dead.  Found the spark plug out and threads in cylinder stripped.  Chased the thresds and the plug went back in snug but would not start.  Going t put in a new plug and try again this morning.

I have done a seach on the forum and found discussions on replacing the threads and the cylinder.  Ok.  Why does this happen?  The threads not strong enough to hold the pjressure of the cylinder firing over the long haul I guess...Stihl you should know better than that!

Question is:  If the plug sets snug should I be good to go if it starts (until it lets go again).  And can there be other damage that would stop it from starting?
Woodmizer LT35HD    JD4720 with Norse350 winch
Stihl 362, 039, Echo CS-2511T,  CS-361P and now a CSA 300 C-O

TroyC

I'd check the coil and plug wire, may have gotten damaged when the plug came out. If some of the threads came out, I would consider an insert of some sort to repair them. If it blew once and is weak now, it will probably come apart again. 

Might not be the case here, but sometimes I've seen plugs that have a short threaded base installed in a head with a deeper threaded hole. Only half to 2/3 of the threads were engaged. Also, if a plug is not tightened correctly, the vibrations as it works it's way out weaken the threads.

beenthere

Would suspect that the plug was not tightened snug, and/or worked more and more loose over time.

But sorry to hear about the problem. Think I'd cut to the chase and get a new top end for it.

Your post did cause me to go check the spark plug on my 362. Was good and tight, but did see some residue on the cover just above the spark plug and the de-comp valve. If anything, coming from the de-comp valve but will keep an eye on it. tks
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

Rhodemont

Started right up and ran great for a few tanks of fuel.  Checked the plug when I was done and it was snug.  I am going to start looking at long term solution of replacing the top.  Hopefully something else does not break down and take priority before I get it done.
Woodmizer LT35HD    JD4720 with Norse350 winch
Stihl 362, 039, Echo CS-2511T,  CS-361P and now a CSA 300 C-O

DHansen

Sounds like you have this under control.  Glad to hear you did not need to install an insert on the cylinder head.

The spark plugs being steel threads and the cylinder head being aluminum, when they work loose, the threads in the head take the most damage.  Spark plugs being removed and installed over time on the same saw can lead to damaged threads.  Too tight on installing the plug and the aluminum threads are pulled and pulled past their yield point.  Too loose and damage caused to the aluminum threads by vibration and blow out.  This is a problem on any brand or any engine with aluminum head.  


DHansen

To prevent this, install spark plugs by hand untill spark plugs gasket or tapper seat on spark plugs base is hand tight to the head.  Then with wrench go 1/8 turn.  Or use a torque wrench to 12-16 ft lbs.  You can look up specifications if you want exact spec.   I see damage to threads often.  And it is most often caused by improperly installed item.

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