Yotaismygame
Juiced Saws #GetJuiced
What say you?
Calling All Saw Detectives
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Lean
Yotaismygame
Juiced Saws #GetJuiced
I'll take opinions first then shed some light.
lack of oil, maybe a little hot but not lean enough to melt the piston crown.
det
Looks as if the cylinder base and crankcase mating surface had an air leak at the base on the left side. Heat failure started on the exhaust side as that is where most of the heat is. Piston top shows good combustion for some of it's life. Curious if cylinder bolts broke on left side or came loose. I'm no expert or detective 4 sure.
I'm not familiar with this model but is the crankshaft not being centered, i.e. too close to the clutch side, a factor?
champion221elite
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I'm no detective, but she's dickered. In for the autopsy results.
brain dead...………..
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I'm no expert by any means= but I have made perfectly good looking pistons look just like the one in your photographs before now!
My guess- going solely off the evidence provided- overheated / overtaxed saw, big saw worked way hard.
Possibly filthy dirty outside the cylinder, blocked up fins equalling lack of cooling- add a big bar and dull chain, repeat heavy load cuts, big bar buried and muffler close to the log face.
Could have been running the perfect fuel oil mix and still result in the images shown, could pass pressure and vac tests and still end up with the results shown.
Was it a dull chain milling saw?
My guess- going solely off the evidence provided- overheated / overtaxed saw, big saw worked way hard.
Possibly filthy dirty outside the cylinder, blocked up fins equalling lack of cooling- add a big bar and dull chain, repeat heavy load cuts, big bar buried and muffler close to the log face.
Could have been running the perfect fuel oil mix and still result in the images shown, could pass pressure and vac tests and still end up with the results shown.
Was it a dull chain milling saw?
Yotaismygame
Juiced Saws #GetJuiced
This has been fun so far...but here's the story
This 371xp belongs to a gentleman well into his 70s. He cuts firewood for a group of guys who donate it to the less fortunate. The saw was originally given to him by a mutual friend of ours, and when it first came into my possession he wanted it looked over and ported. I gave him a smoking deal on the port work and fixed some other minor issues. I used a 268 pop up piston(meteor) and only worked the exhaust/muffler. He didn't need IMO anything over the top but still this saw easily out cut a stock one. Couple weeks later he brings it back. Piston was all chewed up and I found that one of the crank bearings tossed a cage out and chewed it up. So I tore it down and rebuilt the whole thing back in November. I only charged him for parts. Being he's volunteering his time for charity I figured I could too. Now a couple weeks ago or maybe longer he called me saying the saw was hard to start when cold. But after that would fire right up. I told him I would have to adjust the tune in person. Then he calls me this weekend saying he was cutting with it and it just quit running. Compression felt so so. He brings it in and the first thing I do is inspect the piston, then proceeded with pressure/vac testing. Pasted the pressure/vac test with flying colors. Took the carb apart and it's clean. Checked the high jet settings and it was at most 3/4 turn out. Fuel looked like it had oil in it. Aside from many of the bolts holding this thing together being loose(no surprise its a husky) nothing critical was loose and everything appeared to be good. Oh and one last note he had a 32" on it, chain was fairly sharp.
So does this look like a lean issues from user error? That's what I'm thinking. IMO if you want or like to run ported saws you should be well versed in chainsaw maintenance and tuning. I adjust the tune of my saws every time I cut with them.
This 371xp belongs to a gentleman well into his 70s. He cuts firewood for a group of guys who donate it to the less fortunate. The saw was originally given to him by a mutual friend of ours, and when it first came into my possession he wanted it looked over and ported. I gave him a smoking deal on the port work and fixed some other minor issues. I used a 268 pop up piston(meteor) and only worked the exhaust/muffler. He didn't need IMO anything over the top but still this saw easily out cut a stock one. Couple weeks later he brings it back. Piston was all chewed up and I found that one of the crank bearings tossed a cage out and chewed it up. So I tore it down and rebuilt the whole thing back in November. I only charged him for parts. Being he's volunteering his time for charity I figured I could too. Now a couple weeks ago or maybe longer he called me saying the saw was hard to start when cold. But after that would fire right up. I told him I would have to adjust the tune in person. Then he calls me this weekend saying he was cutting with it and it just quit running. Compression felt so so. He brings it in and the first thing I do is inspect the piston, then proceeded with pressure/vac testing. Pasted the pressure/vac test with flying colors. Took the carb apart and it's clean. Checked the high jet settings and it was at most 3/4 turn out. Fuel looked like it had oil in it. Aside from many of the bolts holding this thing together being loose(no surprise its a husky) nothing critical was loose and everything appeared to be good. Oh and one last note he had a 32" on it, chain was fairly sharp.
So does this look like a lean issues from user error? That's what I'm thinking. IMO if you want or like to run ported saws you should be well versed in chainsaw maintenance and tuning. I adjust the tune of my saws every time I cut with them.
What caused lean? 3/4 Hi seems a little lean. What did you have it set at? No limiter cap let it adjust itself?
RED-85-Z51
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From what I can see of the photos, the crankcase seems to show an oily film- don't often see that on a straight gassed saw- how was the interior skirt of the piston- wet or dry and dusty?
Porting puts a little extra demand on the saw from stock- so guess it could have been a tune issue- but I would expect to see more bluing and heat colour on the piston.
Being both intake and exhaust side makes me go back to the overheating overtaxing theory and an oval piston because of it.
Now, if the air tube from flywheel to air box was blocked up........
I noticed the flywheel side case half appears discolored in the photos (when looking down thru the cylinder mounting area). Due to heat? Think it has anything to do with it? Is that the side with bearing issues?
Yotaismygame
Juiced Saws #GetJuiced
Flywheel side case half was replaced. Which is the reason its colored different.
I've never seen a piston top look like this one. Usually after any run time its more of a black oily color. This one is almost completely clean right under the spark plug. IMO I think its user error. ( Tuning, and the way its being used). I can't find anything wrong with the saw.
Yotaismygame
Juiced Saws #GetJuiced
Lol you think I could remember what I set the high jet at for a customers saw I haven't seen since November? 371 never had limiter caps.
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I don't know- maybe your local 70 year old is as fit as a buck rat and can start a reasonably big saw, slam it to WOT and sprint to the log before the saw is warm as suggested by someone that has seen somewhere between six to ten pistons total since first taking a wrench to a powerhead, but that usually displays as a thin concentrated strip of scoring width wise.
Straight gas can migrate around the piston to score the intake side- but then I would expect to see dry gritty underside internals of the piston and dry crankcase. Is there any wallowing of the inside of the piston wrist pin bosses where they would wear against a dry con rod top if it was severely lean fuel mix?
Cutting firewood is way more taxing than felling, if the owner is anything like me, the saw is run pretty much WOT for the entire fuel tank as you work down the log, fill it up and do it again....... which takes us back to overworked/overtaxed heat seize.
Do you know the species he was last cutting, size of the log, duration of the session, weather conditions?
Straight gas can migrate around the piston to score the intake side- but then I would expect to see dry gritty underside internals of the piston and dry crankcase. Is there any wallowing of the inside of the piston wrist pin bosses where they would wear against a dry con rod top if it was severely lean fuel mix?
Cutting firewood is way more taxing than felling, if the owner is anything like me, the saw is run pretty much WOT for the entire fuel tank as you work down the log, fill it up and do it again....... which takes us back to overworked/overtaxed heat seize.
Do you know the species he was last cutting, size of the log, duration of the session, weather conditions?
