Diagnosing what caused burnt piston/scoring?

[angelo c]

we had a new husqvarna 395 with 36" bar come back less than a week that was scored. Gas was good, no air leaks and tuned properly. The chain was super dull and the guy reefed on the saw so hard the rear handle was hitting back of the saw. The heat created from running a dull chain killed that saw.

the Chain is the first thing I check on a blown top end...then the mix...then the carby settings( if no-CM) then pop off the muffler....ect

you'd be surprised how many times a bad operator blows a saw motor....but never any other piece of eqt...reefing on a weedwacker or backpack blower is dumb but a $1200 saw is ok to abuse the chit out of...

 

[lehman live edge slab]

Personally I’d get the 11$ gasket set and a meteor piston set. After I made sure cylinder cleaned up of course, then put it back together with new fuel line for 10$ and a new impulse line also about 10$ for oem. Inspect the intake boot throw a 5$ carb kit in and you should be able to have a running saw for 75$ or less if you fix yourself. Oh also check to make sure the pto bearing is tight and not the cause of an air leak. As long as the bearings are tight no need to pull saw down all the way just use the base gasket and crank seals out of kit. After it’s together and make sure you start with the I initial high and low settings of 1-1 1/4 turns out. As long as your close in that range after finial tune on a stock saw you shouldn’t have any air leaks but if you end up 2-2 1/2 turns out on that jets I’d look for a faulty carb or an air leak that still exists.

 

[Marshy]

the Chain is the first thing I check on a blown top end...then the mix...then the carby settings( if no-CM) then pop off the muffler....ect

you'd be surprised how many times a bad operator blows a saw motor....but never any other piece of eqt...reefing on a weedwacker or backpack blower is dumb but a $1200 saw is ok to abuse the chit out of...

Eggsactly. I watch a guy toast a 660 2 weeks ago by pushing it through a stump (with the grain, like milling) with a dull chain. Just constantly stalling the chain by forcing it. The chain was dull and engine over worked... poof. The only reason his 372 didnt burn up the same exact way was because it cooked the coil first and lost spark. Cant fix stupid.

 

[Wonkydonkey]

@Al Smith could you tell more on the 026 muffs, as i'd be interested which was the most and least restrictive

Cheers..

 

[CrystalRiver1]

Another option, you mail it to me, I will rebuild it bottom to top mechanically and send it back to ya. I have tons of 026 parts in my inventory just itching to move along. Send me a PM sometime.

Hmm...sounds intriguing and I appreciate it.
BTW...in all due respect Basher, what would be your fee$$ and motivation for doing such a great deed?

 

[blsnelling]

My money is on a leaking flywheel side crank seal.

 

[Al Smith]

@Al Smith could you tell more on the 026 muffs, as i'd be interested which was the most and least restrictive

Cheers..

I'm a simple man ,do things the simple way .The idea is to cut the restrictions on the idea if the fuel charge cannot get out it cannot get in .My way is to completely gut the muffler. All that will be left is the shell .I mean all deflectors ,baffles screens .
Some complain about the noise but keep in mind I was used to reed valve McCullochs so it doesn't bother me .
I play it safe on the actual muffler out let size and only enlarge the area to about 80-85 % of the engine exhaust port .Keep in mind a pressure can muffler also acts a pressure regulator .With no restrictions you could get what's called a "short circuit effect " blowing a portion of the incoming fuel charge right out with the previous exhaust .What ever you do retune the carb so it doesn't run out lean .
Now that said if the question was with regards to stock OEM mufflers I'd have to get out the manual that is as large as the unabridged version of Websters' dictionary to find the numbers .

 

[Al Smith]

@Al Smith could you tell more on the 026 muffs, as i'd be interested which was the most and least restrictive

Cheers..

Well early ,the chickens aren't even up yet .As far as numbers which quite frankly will about cause you go blind looking at them I found this .
Two muffler backs 026 one 024 making three assuming the 024 and 026 interchange .One is listed as fire safe assuming that means more restrictive #1121-140-0601 .The other two backs #1121-140-0603 ,026 and 1121-145-700 024 it's hard say not having either in front of me .
Two covers I have found used for both saws .1121-145-0800 and 1121-140-0800 .It appears to me the first number would be less restrictive by looking at the drawing .

 

[Al Smith]

Now in case anybody has not seen one this is what you dealing with trying to look up parts numbers and this doesn't even cover the newer saws and equipment like weed wackers ,blowers etc .Then you have CD's ,micro fitch in addition to 15 pounds of paper .
If that's not enough ,that's only one brand .Add to that Homelite .McCulloch etc and it almost gets overwhelming .

 

[Wonkydonkey]

Well the ipl I have is a bit diff from your book, as well as diff part no’s. But I think I see what your saying no 18 looks like no baffle and 19 is the fire safe. And 23\24 is the cat
Here we have no 15 & 16. I’ve done what mustangmike does on his saws, drill a hole in the baffle and open up the outlet hole a bit.

 

[Basher]

Now in case anybody has not seen one this is what you dealing with trying to look up parts numbers and this doesn't even cover the newer saws and equipment like weed wackers ,blowers etc .Then you have CD's ,micro fitch in addition to 15 pounds of paper .
If that's not enough ,that's only one brand .Add to that Homelite .McCulloch etc and it almost gets overwhelming .

Media Cat was a better choice but even that is outdated now Stihl changed their system. # 15 and 16 are the easier mufflers to modify , they all need it as the flow restrictions choke up even a stock engine, once ported they need an extra outlet.

 

[Al Smith]

That's a revised list evidently .I see where it lists a decomp valve which was not used on the early models .Plus it gives the screw sizes and bearing specs .That's a better list than I have .

 

[RI Chevy]

Muffler front cover #19 seems to be the most common. At least for all the 026s I have seen.

 

[Al Smith]

I'm not certain what gets more traffic, mix oil ratios ,ethanol gasoline or mufflers . On the later I just always figured rather than buy more of them to experiment with would soon tally up to more money than the saw is worth .20 minutes /half an hour with a good die grinder would solve the problem .Simple as that .