Hi everybody, so Recently I rebuild a Stihl 044. I put new bearing, new piston with rings, and a new cylinder into this saw. The only thing I reused was the crank.. so after about a week of cutting with this saw it totally grenades on me. After taking the saw apart again I noticed the crank was totally shot.. I’m wondering if the crank giving out caused this damage orrr if the damaged cause the crank to go out. Maybe there was to much compression after adding the new piston with rings? I could use some help lol thanks
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It would appear the gouges on the piston were caused by the broken ring.....Would be interesting to see the crankshaft.
drf255
BAD CAD
That’s some serious carnage. Something came loose in that motor and fried everything. It coulda been the large end crank bearing, got a crank pic?
What was damaged before you rebuilt the saw? You could rebuilt something that was destined to fail again.
I had a bad crank in an 036. I kept scoring pistons no matter what, went through 3 slugs before I realized it was the large end of the crank that was damaged and spitting out little metal bits. If I hadnt checked, eventually larger pieces woulda come out and done what happened to your saw.
What was damaged before you rebuilt the saw? You could rebuilt something that was destined to fail again.
I had a bad crank in an 036. I kept scoring pistons no matter what, went through 3 slugs before I realized it was the large end of the crank that was damaged and spitting out little metal bits. If I hadnt checked, eventually larger pieces woulda come out and done what happened to your saw.
looks to me that det killed the rings, and the broken rings have scrapped the engine
drf255
BAD CAD
Agree that a ring was the final gouging culprit. But the top of the slug is either detonation or some debris bounce around that caused the ring to fracture.
Looks more like debris floating around than detonation.
Looks more like debris floating around than detonation.
So I just went and took some photos of the crank. You can definitely see where the bearing split. I don’t think there was any detonation, when I opened up the muffler there was so much aluminum. I believe that’s what caused the damage to the top of the piston
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drf255
BAD CAD
Bingo
Debris came out, took out ring, more carnage.
Doubt that the crank was secondary damage, I bet it caused the rest. The large end bearing inspection isn’t so easy. I bet the crank caused the first failure too.
Debris came out, took out ring, more carnage.
Doubt that the crank was secondary damage, I bet it caused the rest. The large end bearing inspection isn’t so easy. I bet the crank caused the first failure too.
that crown looks like classic det texture to me
here a piston i detted with too much boost (and it killed the bigend too)
here a piston i detted with too much boost (and it killed the bigend too)
Hmmm I guess I’ll try to inspect those bearing alittle bit more before I reuse one again.. could I have been the new piston and rings that broke it? Maybe alittle to much compression for that old crank?
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drf255
BAD CAD
Your piston is “peppered” like detonation will do. Detonation uncommon in saws, especially stock ones. Saw are only at around 6:1 static compression, even ported they get nowhere near the detonation range, but it does occasionally occurs with too much timing adVance and a lot of heat/comp in a ported saw.
His slug is dented by a foreign body.
drf255
BAD CAD
Doubt that. I’ve run 044 with 240 psi and no issues for years. Stock they are around 150-160.
Everything has a life expectancy, including crankshafts. I bet the cage was fractured before you assembled. I also wonder if whatever small metal fragments broke loose fried the old top end and it was misdiagnosed. I usually clean cranks with brake clean, then rotate and slide the rod from side to side. If there are not any cracks in the bronze cage and there is no radial play at all, they are good.
Only bad issue for you is that 044/440 cranks are getting rare. Usually gotta but a case and harvest the crank. Is your saw a 10 or 12mm crank? Looks like a 12 from the pics of the crank.
It’s a 12mm So it’s not as hard to find parts. I did manage to rebuild the saw again. I had to use piece from three different saws. I do have another question tho.. So I put this saw back together with a better crank and a extra used piston and used cylinder from two different saws.. Its works okay but the compressions alittle low. Is it bad to keep swapping piston ring? The compression isn’t horrible but it could be better. I don’t wanna wreck the cylinder by swapping out 2 different sets of rings in short time. Thanks again for the help
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A set of new Cabers is not much $ compared to time spent fixing a saw.
Concerning used P/C parts and mix and match. Do you check that P/C clearance is reasonable?
Your piston looks like some of my dirt bikes from years ago when big end rod bearing let go.
Found that too, cheap rings on the market from you know where don't cut it, sometimes even out of round, I have quite a selectin of Cabers and meteor pistons etc on my shelf, the cabers are made of a different material with a lot of spring to them, if your cylinder is good there is quite a noticeable difference especially in the long run, if you are using used rings that can be your problem as well, especially if they didn't come out of that cylinder.
I already ordered a new set of stihl rings but I would like to use the saw for work this week. Is it gonna harm the cylinder by using rings from a different cylinder? I fired the saw up and it ran okay
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IMO only, it probably won't cause any problems if they are in good shape, what was your ring gap? might just be worn beyond spec or lost their tension.
