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merc_man

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If he was flush cutting a stump that would dull chain pretty fast causing higher rpm which would mean longer cutting more heat and probly leaner. Cheack of chain is real dull or mabe he reaharpened it to cover it up.

Just giving ya ideas.
 

paragonbuilder

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If he was flush cutting a stump that would dull chain pretty fast causing higher rpm which would mean longer cutting more heat and probly leaner. Cheack of chain is real dull or mabe he reaharpened it to cover it up.

Just giving ya ideas.
Tree guys around here aren't that smart... Lol
 

paragonbuilder

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Check it with wd40 when your done. If there is a leak you will find it.


Sent from my iPhone using Tapatalk
 

Landmark

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The most discouraged i have got was a 371 that i couldnt seem to get right. Had two p/c's fail on me and couldnt figure out the problem. I stepped back got another cylinder and finally got it right. Have no idea what was going on but it cost me some money to get the saw back to the owner. No real point to story just take the good and the bad and do the best you can. And when all else fails build a 262. That always seems to pick me up.
 

Chainganger

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I have never learned a thing doing things right, only when I did things wrong. Today I made two mistakes working on a saw (did not know what I did not know). Cost me 2 separate trips to the hardware store. Now I know those two things, I wish that was the end of it, pretty sure there are a lot more mistakes to be made and a lot more trips to the store.
 

Mattyo

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just fyi ...landmark.... that 371 cylinder that failed so many times, you sold to me. its in this vid....and is the faster of the two saws...


that saw now has 220 psi comp.... and runs fine, if you can start it hehe

I learn from my mistakes too, but in this case, I can't find my mistake. ...if I can't find my mistake, then there is nothing to be learned ... so then I have two choices....throw money at the problem and pray, or give up...
 

Landmark

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just fyi ...landmark.... that 371 cylinder that failed so many times, you sold to me. its in this vid....and is the faster of the two saws...


that saw now has 220 psi comp.... and runs fine, if you can start it hehe

I learn from my mistakes too, but in this case, I can't find my mistake. ...if I can't find my mistake, then there is nothing to be learned ... so then I have two choices....throw money at the problem and pray, or give up...
Glad you got it going and the one i got from you is the one that solved my 371 problem. Funny how things work. And i dont think you'll take the give up problem. 'I can't" isnt in my vocabulary, and if i cant do it i still wont admit it easily. Ha
 

jbgrant

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This thread is almost 5 years old, but I didn't see a good explanation for the top end failure on Matt's 372 build and I think there is a pretty likely one:

When I rebuild a saw (with a new or honed cylinder, new/cleaned piston, fresh ring) the compression will increase about 25-45 PSI over the next 3 fuel tanks during break-in. Any significant reduction in blow-by and the corresponding increase in compression (during break-in) WILL result in a LEAN operating condition!! It has been my experience that the higher the increase of compression during break-in, the more the carb must be richened to compensate. I suspect this is due to the more complete combustion that is occurring as the piston/cylinder leak less and achieve a better, more complete burn (but I do not know for certain).

If Matt's 372 did not have a couple of tanks through it, and this guy he sold it to did not have solid experience keeping a fresh saw in tune...then it is very possible that 10-20 minutes of break-in resulted in a big increase in compression and things got too hot (lean) leading to softening of the alloy. If so, this could have been prevented with better break-in procedures and frequent carb adjustments. Another safe measure would be to send the saw out of the shop excessively rich, and tell the new owner to bring it back after 2-3 full tanks for tuning.

Just my initial thought and I was surprised nobody mentioned this.

I can build a saw....I can't necessary guarantee its reliability

:(
 
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Mattyo

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I dont really notice that big of a compression increase after break in. But certainly tune needs to be checked. Lots of things go wrong first few tanks....

These days I haven't been selling too many saws....and at this point try to only sell to folks that will pay attention to tune...and to doing bolt checks. The bolt checks are super important.

Another thing I've come to do is have saws go out into the woods for a tank or two before they are sold. Building a saw from ground up needs kinks worked out for sure. Then I pull the muff after a few tanks and check the piston. If its nice I send the saw out. Just how I've come to do it.
 

drf256

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This thread is almost 5 years old, but I didn't see a good explanation for the top end failure on Matt's 372 build and I think there is a pretty likely one:

When I rebuild a saw (with a new or honed cylinder, new/cleaned piston, fresh ring) the compression will increase about 25-45 PSI over the next 3 fuel tanks during break-in. Any significant reduction in blow-by and the corresponding increase in compression (during break-in) WILL result in a LEAN operating condition!! It has been my experience that the higher the increase of compression during break-in, the more the carb must be richened to compensate. I suspect this is due to the more complete combustion that is occurring as the piston/cylinder leak less and achieve a better, more complete burn (but I do not know for certain).

If Matt's 372 did not have a couple of tanks through it, and this guy he sold it to did not have solid experience keeping a fresh saw in tune...then it is very possible that 10-20 minutes of break-in resulted in a big increase in compression and things got too hot (lean) leading to softening of the alloy. If so, this could have been prevented with better break-in procedures and frequent carb adjustments. Another safe measure would be to send the saw out of the shop excessively rich, and tell the new owner to bring it back after 2-3 full tanks for tuning.

Just my initial thought and I was surprised nobody mentioned this.
I’ve noticed the exact opposite, though I make certain the saw is fat upon initial run and do continually adjust during the first few long cuts.

Your assessment makes complete sense, as more compression generates more heat in the charge. The hotter a saw gets, the fatter it needs to become for proper Stoichiometric ratio.

As my saws break in, they tend to become fatter and fatter sounding at the same needle setting. I believe it’s less friction inside the cylinder which causes less load on the saw-just like when one comes out of a cut and listens to piss rev. That has become the norm for me and how I tell people to tune their saw. I tell them to “listen to the saw, not me, as to what rpm to tune to”. As the rings set, the saw will want less and less fuel to be tuned correctly-it will have less load on it freespooling.

This may be a factor of initial vs eventual break in. The beauty of Autotune is that it’s does it for you. Many of us still suspect the the factory settings/software have a built in breakin curve that goes away after X amount of time.

Fatter is safer. On a ported saw, there can be a 1500 rpm window for ear tuning. Fatter is also generally faster for a work saw-racing is another story. Just above not blubbering in the cut seems to make the most torque, at least for me.
 
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smokey7

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My builds lean out with heat. My saws will be kinda fat just walking around the log pile cutting. But will be on the ragged edge on a long hard stump cut or a few long full bar cuts. Never smeared a piston but I'm sure I've been very close.
 
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