PB
Addicted to ArboristSite
Does anyone have the Jonsered piston failure guide for download or sale? Might be a good bedtime read.
I found this.
:hmm3grin2orange: :hmm3grin2orange: :hmm3grin2orange:I have a Stihl book on piston failures, but oddly the pistons in the book are
all jonsereds and Husqvarna's................
I have a Stihl book on piston failures, but oddly the pistons in the book are
all jonsereds and Husqvarna's....................
Seriously, I was tempted to e-bay it
turbo charger running a too higher boost
This is what I know, the spark arrestor was pretty gummed up, he ran cheap 32:1 oil and probably 87 octane gas.
When you say burnt up, do you mean that the aluminum is damaged (melted, hole in piston) or do you mean that their is a thick coat of a hard rough black substance (carbon) on the piston top.
I think an overnight soak in some sea foam and a little elbow grease might show that the piston it's self is just fine, if this is the case you answered your own question as to what caused it.
Timing very slightly out
Wrong octane fuel
carbon build up around plug / cyl causing pre ignition
wrong heat range on spark plug
turbo charger running a too higher boost
In that case sounds like detonation due to pre-ignition. Steve covered some of the possible causes pretty well.
Your gonna have to crank that Turbo charger down some.
Check the flywheel key as was said before, this a pretty rare failure but not impossible and it wont take 5 min. to check. I'm sure you got the saw in the condition it's currently in so you wont know if the ignition is functioning properly until you get the saw back together. At this point I would say buy a new piston and put the saw back together. Make sure you have the proper plug in it and that the flywheel gap is correct. And see what you have then. Pre ignition can be caused by several different causes but if all of the timing issues check out I would say it is probably due to carbon build up and cheap gas. When carbon builds in a cylinder it can get hot and start to glow. When this happens the spark plug and ignition system are no longer in charge of when the fuel/air mix is ignited. The problem is only made worse by the lower flash point of the low octane fuel (always run good fuel folks) and the charge is free to detonate before the ignition fires the plug and timing issues occur.
In short if you can’t find anything wrong with the saw clean up the cylinder buy a new piston & rings put it back together with the proper plug and good high octane fuel and see how she runs. Good luck
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