This is a piston from my TS760 Stihl cutoff saw. My guys rolleyes said that it had merely run its course and died. The inner filter was slightly off the seat when I inspected it, the outer filters were secure. But can this be from some dust in small amount of time, OR does this look like regular gas being put into a 2-stroke $1,400 saw? Either way, the bottom is still smooth, so I am doing the top - I was just looking for opinions.
It looks like thermal nuclear meltdown, no oil inthe fuel would normaly sieze it up but I would say lean out, someone messing with the high speed jet
Tool - Is that the exhaust side?? Do make sure you find what caused it before doing the top end and have it happen again. The air filter leak could have been the problem letting in to much dust particles . Were you cutting dry or wet? I would definitely put in new crank seals just for good measure . Make double sure the gas is mixed correctly or richer than recommened. Check that the carb intake boot is not cracked or leaking. Good luck with it. Doug
all good stuff to look for, but I have to add that my brother is an arborist and he runs only big stihl saws, and every once in a while one just hits the point and ends up looking just like that. I think hard working 2 strokes are always working right at their limits.
Looks like lack of oil to me-thats what the piston in Dad's Lawnboy looked like after I added what I thought was 2 stroke gas and mowed the yard. It REALLY hammered at the end.
Looks to me like it ran on strait pump gas, with no oil. Just like the piston in my mothers weed-eater when she poured strait gas in it, then couldnt figure out why she couldnt pull the rope after it died! Jason
Looks to me like a case of either no oil, or at least not anywhere near enough oil. Got to love guys like that. "I don't know whats wrong, it just quit"
if its dust it will normaly were the intake side of the skirt, leaning out the exhaust side ,from heat, and no oil the skirt all around but worst on the exhaust side. is the small end pin showing hot marks? the spark plug tells alot too about tune .
That looks identical to many I have seen from Stihl before they improved their air cleaner system. I'd need to see the whole piston and head but its looks like dust to me.
I am not sure what the cause was but if it was no oil then I would be looking at the bottom too since it also depends on the fuel mixture for lubrication.Ron G
Thanks for the input, guys. The pin and the bearing are fine, not even discolored. The enjgine still turned over easily....TOO easily.:tong
For my two cents it looks like a lack of oil as the lack of ceramic on the piston would exclude the dust theory.
Then its almost certainly the dust. I chernoybled a Husky last year that was almost 6 years cutting dry and the piston is very much the same. You crack a ring out and it bashes the head. The rest turn over fine.
Starting to reach that conclusion. The innermost filter was off the seat (you must manually push it down on the older Stihls inside the larger one). Plus, I mixed the fuel and set the high and low on this carb myself....and Lord knows I myself never make a mistake.
The heat pattern is wrong for a lack of oil failure. The Stihl's are a little fiddly in their air-cleaner arrangement and lack adequate surface area for dusty operation. My Huskies have twice the surface area of foam and will still be well clogged after a couple of days hard work. I carry two spare foams in a zip seal bag all oiled up ready to go. Washing the foams is way cheaper than buying paper elements. I spoke to Husky when I chernobled the 3120K (120cc) and said to get the foam almost dripping with filter oil. I couple of my competitors (who cut dry like we do) don't do a lot of servicing and the blow a Stihl Qwik Cut in about 12 to 18 months. The pistons are always identical to yours.
could be a couple of things. if its on the exhaust side it was ran a little lean and got hot if it was on the intake, i would say it's no oil. those are just two and either one maynot be right Pj
If it failed due to lack of lubrication there would be a big round blue and black ring on the underside of the piston and also visible in the top, as well the skirts would show the expansion and heat marks typical in two strokes running lean. This is a mechanical failure from FOD ingestion over time. I spent some years doing engine failure analysis for a living and this is typical...almost classic. The fact that the bottom end is fine also tells the story.
There's your money quote. I agree with Squizzy. Remember folks, the reason two strokes, like chain saw engines, mix oil with gas is mainly to lube bottom end since they don't use crankcase oil, not necessarily for lubing top of piston where failure occured. Yes, the gas/oil lube is necessary for lubricating rings and piston interface with cylinder, but if this piston/ring failure had occured from prolonged lack of lube, the bottom end would be hammered as ugly as the piston. My 2 c
Maybe dropped a valve, then??? ocr
i was primarilly talking about cylinder score. how about a pic of the cyl?.....if you can get youre camera in there lol as far as the Valve thing.... not all 2 strokes have them. Pj
Well, I can't get in there, but here you can see the scoring up and down both intake and exhaust ports (same side on these things). I am throwing in a pic of the small end needles for good measure.:tong OCR - no valves on these, they are the same as the big saws - as a matter of fact, the bar oil port comes with a plug from the factory, but the case still has the raised "oil" inscription on it.
special tool, I think you need to edit your "looking for wife" sign. "Must have John Deere tractor and barn, and Stihl chainsaw "
Yeah - you know my wife has one of those wiseacre equestrian bumper stickers that says, " my ass is too big, but I married him anyway". So I'll be lookin' for a tractor and barn.....
Man...that's just cold!
Lol... that was a remark, meant for my ?? friend ?? Squizzy and his FOD (Foreign Object Damage or Foreign Object Debris). Then, if he said anything about "valves", I was going to feign a compromised password, and somebody using it to make me look... well, ignorant... did it all by myself though... ... lol Notice the small case and size ocr , it's usually caps. and regular size... oh well, a failed plan... Serious now though... He's right about FOD, it can be a major problem with jet engines (no valves either... lol) too. Here's a pretty good link: http://en.wikipedia.org/wiki/FOD OCR... I thought ATCO might "correct" me too... and I had a better plan... lol
The Phoenix will rise again.....
still quickcuts We have 6 ts 460s that have a habit of destroying pistons. the guy who used to repair them has moved on, so now its my turn. just pulled two down and found as per photo ring land broken and rings broken up damaging barrels I don't want to replace pistons and barrels and have this happen again any advice much appreciated
Sandy, this why I had to go away from Stihl. The only solution is to increase your oil in the fuel mix slightly and change/wash your filters lots more often. As I said above; I carry spare foam elements already washed and oiled ready to go. This way, when we are working them hard it only takes a few minutes to change the foam and get working. Also, increase the amount of oil in the foam, don't squeeze it all out. This is the only way to keep them going. My Huskies have a much better air filtration system than the TS 460 but you still have to do them regular. A week is a long time when you are working them hard in dusty conditions. You can either service the air cleaner regular as clockwork or keep on re-building. The tree lopper guys don't suffer the same problem I think for two reasons: 1) Particle size is bigger so there is less fine dust getting through...and its wood not concrete or stone 2) Those guys clock up so many hours so quickly usually the whole saw is worn out in less than no time. I got 5 1/2 years out of my last Huskie and I now have the Husky/Partner K1250 (16"). I expect to get 10 years out of it with a good filter regime. Many guys I know don't get 2 years out of the Stihl but they don't do the servicing. A guy that I started off working for has a TS 460 which must be at least 8 years old now. Every Saturday you can see him at the yard cleaning it and servicing the filters.
looks like a spun ring to me i dont know how firmiliar you are with two strokes but the rings are stationary on the piston versus a four stroke where the rings are free to spin in the groves of the piston a spun ring means that the ring spun over the keeper pin in the ring grove and by doing so the end if one of the rings caught a valve and broke it off hence leaving a exposed sharp point or that broken piece of the ring got wedged between the piston and cylender wall and went up and down a few times
I started using Amsoil in all my engines best thig I ever did. I have a partner 750 cut off saw, start it it is wide open and still wide open when it gets shut off and Turbo even has used it. Since the oil switch the thing starts easier. My 1995 K 3500 rolls down the road weighing in at 13,000 lbs & 250,000 miles on it I put Amsoil in that it runs cooler and starts easier. After you put it back together put some Amsoil in it you will be happier, by the way this is not a commerical endoresment for Amsoil, lol digger
Back together and running like a raped ape. Going on the cart to cut about 130' for 24" ADS tomorrow.
piston fuel to lean
Looks like the mixture was wrong or perhaps no oil at all.