wood dust in the carb hard on the saw?

[rogue60]

I put a new chain on one day and some how during this process sawdust got in the muffler and blew the bottom end!.

 

[bwalker]

The story has not changed. I always said it failed due to sawdust getting into it. That clearly wore it out.

Congrats. Add lieing POS to your resume.

 

[bwalker]

Definitely not a lean seize. I have always used a 50:1 ratio for that saw.

Lean refers to air to fuel ratio smart guy.

 

[bwalker]

OK, troll. How do you explain an immediate lo9ss of compression and performance?

Air leak would be my guess, but I have a feeling you could screw you about anything.

 

[bwalker]

I once had. A stick poke a hole in the air boot on a cr250 Unbeknownst to me. It ran all weekend without losing power or seizing and this was in sand country. Granted the piston was polished smooth and the bearings where not looking good, but it never died.

 

[PapaWhitebeard]

Anecdotal evidence, but I think still worth the mention...

At my Echo Dealership, the Service Manager showed me a top end that had, what to me, seemed like an odd colour. I asked about it, and he said.. " It's from wood dust getting past the filter.: There was an odd "burnished" look.. a kind of light brown / tan colouration that I'd not seen before, I asked if that was why the saw was in pieces on the bench, and he said no.. The wood ingested, is burned up during normal combustion, and just resulted in some discolouration. Sawdust isn't capable of scratching metal in small quantities. Remember, the fines would be sucked into the combustion area, and burnt immediately to ash. Fines or ash, even if a very, very small percentage of them got stuck between the piston and the sleeve, would have minimal effect or consequences to the saw. They simply deposit, what is probably basically creosote on the piston dome, and on the top of the combustion chamber. That was the discolouration that let them know that the filter was letting stuff get through. That, and the presence of fines where they shouldn't have been in the induction area of the saw.
Are fines good for a saw? Uhhhh... no!! Do they cause catastrophic failure? I sincerely doubt it.

Wood doesn’t destroy pistons—you’re right it simply burns. Dirt, grit, rock dust metals dust… yeah those will destroy pistons.

In the OPs case the symptoms of saw not running great occurred after spark plug change. So Occam’s razor it’s related to that—either the plug wire was fragile and broken already and manipulating it to replace the plug broke it more. (Spark from the coil is crazy hot and will jump across broken plug wires with ease) but if course the wider the gap the worse the saw runs…

No doubt the saw had scored pistons… but it wasn’t from the spark plug change. Scoring from leanout failure takes a long long time. This saw probably had scoring for a good long time and ran just fine.

I’d bet that either the plug wire was damaged and that damage was exacerbated during the plug swap. Or the gap got smashed but OP is confident that didn’t happen and I have no reason to doubt him.

But I’d also bet money the mechanic who bought the saw for $150 replaced the plug wire and put a new piston in it and that saw is running today. Or if he’s dishonest he replaced the plug wire and someone else is running it with the scored piston right now.

Unless OP was there to witness the compression numbers on the gauge I don’t believe the dealer saying it had low compression. Dealers have enormous pressure to move inventory. They gotta sell saws. Every month they sit on the shelf in inventory costs them money. They get incentives based on the volume of sales. Most shops make more money on SERVICE (repairs) than sales… but they’re in the sales business. They gotta sell inventory.

In California right now there are almost no gas powered saws available off the shelf. You have to order them. Because my dealer doesn’t want to carry the inventory. It costs him too much. That and California is pushing hard for everything from cars to chainsaws converting to electric…. But even the electric saws… the only thing they have on the shelf are the budget consumer grade type for joe homeowner.

Dealer has a 500i on the shelf that is a very expensive saw he sells for not much over his own cost? I say he was under inventory accounting pressure to get it off his shelf.

 

[PapaWhitebeard]

I once had. A stick poke a hole in the air boot on a cr250 Unbeknownst to me. It ran all weekend without losing power or seizing and this was in sand country. Granted the piston was polished smooth and the bearings where not looking good, but it never died.

LOL I love it!

One, the CR250 was an absolute MONSTER of a bike and I loved loved loved riding them.

Two, Honda makes absolutely amazing machines… if it was a four stroke you would have seized but because we ride oil burners you had enough lube to make it through the weekend.

Ahhh that brings back memories of the 80s… thanks, man. I love that stuff.

Yours truly on my 1983 Honda XL200R (my streetbike at the time)

 

[PapaWhitebeard]

Congrats. Add lieing POS to your resume.

LOL somebody lied for sure. I suspect it was dealer and OP is just (rightfully) pissed about this. And it’s never fun to realize you’ve been lied to and taken… but… nobody died… and he’s got a 500 now… so… the moral of the story is don’t trust dealers and don’t let dirt or metal into your intake

 

[ZeroJunk]

The dealer thought so, too. The only good thing is that, after they told me repair would be $1100 for a new block, piston and crank, they offered me an MS500i for $1180, which I accepted. What an upgrade! It not only cuts faster, it cuts more per unit of fuel used.

Just for perspective, the MS170 type saws always have sawdust around the filter if used to amount to anything.
Weedeaters and blowers come in somewhat regularly with no filter at all.
And, I got an 044 in one day this week with no air filter.

So, would I run mine that way ? No. But, it is a slow death.
Now, you could have had some piece of plug thread, that type thing.
Sawdust. No.

 

[Chucksta]

It would seem that Bwalker is in a bit of a mood today..

Gonna grab a cold one and some popcorn, sit back and watch the magic..

 

[HansFranz]

Scoring from leanout failure takes a long long time

Really?

I would have thought that an air leak causing a "leanout failure" would scuff and score if not seize a saw dam fast at high load and high rpm (in minutes if not seconds)...is this not the case?

 

[sean donato]

Depends on the severity of the air leak.

 

[PapaWhitebeard]

It would seem that Bwalker is in a bit of a mood today..

Gonna grab a cold one and some popcorn, sit back and watch the magic..

Idk Bwallker from Adam but he used to ride a Honda CR250 two stroke… one of the best motorcycles ever made in the history of time… so… I automatically like him

And nobody thinking about the good old days of jamming around on that truly mind blowing machine (really and truly even 30 years later the very best 250 two strokes aren’t appreciably faster and the fox shocks they had on the CR250 is just as good as and WP or modern shock) if you ride dirt bikes even THINKING about that bike will put *anybody* in a good mood

So my personal prediction is “there will be no interweb fighting today” and possibly an admonishment to me for going off topic and the start of a new two stroke moto thread wherever those are supposed to be (Bwalker I have a Husqvarna 125 in my shed this minute… it weighs 178 lbs wet and is the most fun little toy to ride)

 

[PapaWhitebeard]

Really?

I would have thought that an air leak causing a "leanout failure" would scuff and score if not seize a saw dam fast at high load and high rpm (in minutes if not seconds)...is this not the case?

I’ve seen guys run 25:1 because they foolishly thought it would lube better. This is on race motorcycles that are built for maximum power and require rebuilding after ~80 hours. Even on that bike after two days at the racetrack (call it 12-16 hours max) the only damage we could see was super ugly spark plug. Eventually he would have experienced sever scoring on the piston but no, it doesn’t happen instantly. I imagine (don’t know for sure) that any amount of lean fueling sufficient to cause immediate damage wouldn’t provide enough fuel to let the motor run.

Is running it too lean bad? Yes. It will cause premature wear. And yes scoring on the piston. But not in an hour. Not even in a day.

Anyway you asked, that’s my experience. And yes I’ve seen plenty of guys running lean for power grenade motors… it happens. But usually near the end of the season in my experience. And FWIW I’ve been riding since the 70’s have far more than 10,000 hours on bikes, was a racer and for some number of years was a professional. Before and after I had my own team doing the wrenching I did it (and am back to doing it) all myself.

But I love moto talk and 2 stroke motor talk so I will blather about those things pretty much as long as anyone will let me

Best,

Woody

 

[PapaWhitebeard]

Depends on the severity of the air leak.

depending on where the leak is, if the leak gets large enough the motor simply will not be able to idle. Bigger leaks it will fire on startup attempt but not be able to run.

But you’re right if it’s leaking enough to still run but be severely lean it’s gonna for sure result in piston damage. I think the engineers call it detonation damage or something. That’s where my expertise ends (not an engineer )

 

[sean donato]

depending on where the leak is, if the leak gets large enough the motor simply will not be able to idle. Bigger leaks it will fire on startup attempt but not be able to run.

But you’re right if it’s leaking enough to still run but be severely lean it’s gonna for sure result in piston damage. I think the engineers call it detonation damage or something. That’s where my expertise ends (not an engineer )

Detonation could be caused by running lean, but not usually in a saw in my experience. Running lean does certainly heat a saw up quick though.

 

[Bob Hedgecutter]

I wrecked an MS441C while changing the spark plus. I did not clean the area around the spark plug carefully enough, and the cylinder was scored, resulting in loss of compression. Sawdust was the culprit, though it may not have been just "fines".

We need to know a back story, like what caused you to change the plug?
Was the saw getting hard to start and you decided a new plug might be the answer?
Photos of the piston, old plug, new plug would be handy to back up your claims.

 

[Hermio]

Yeah im not saying you smashed the gap… I’m just saying all kinds of stuff can happen.

And you’re right that’s a damn good price for the 500

I’ll be really interested to see how you like the fuel injection especially after a year or two. I think about motorcycles and chainsaws as basically the same kinds of animals and when they rolled out fuel injection on 2-stroke KTMs I was racing in ~2018 it was *amazing* and even though it took them a few years to work out the bugs and it requires a computer to work on it it’s hard to argue with the results they are getting with them now..

I have only one complaint about it. When it has been idle a week or two, it tends to stall out after running for a second or two after starting. This can happen 2 or 3 times sometimes. My theory is that the microprocessor "forgets" where it operated before shutting down, and there may be a capacitor or something that supplies power to the system memory for a while. Once it has run for 5-10 seconds without stopping, I can shut it off and it starts again with one pull.

 

[Hermio]

Anecdotal evidence, but I think still worth the mention...

At my Echo Dealership, the Service Manager showed me a top end that had, what to me, seemed like an odd colour. I asked about it, and he said.. " It's from wood dust getting past the filter.: There was an odd "burnished" look.. a kind of light brown / tan colouration that I'd not seen before, I asked if that was why the saw was in pieces on the bench, and he said no.. The wood ingested, is burned up during normal combustion, and just resulted in some discolouration. Sawdust isn't capable of scratching metal in small quantities. Remember, the fines would be sucked into the combustion area, and burnt immediately to ash. Fines or ash, even if a very, very small percentage of them got stuck between the piston and the sleeve, would have minimal effect or consequences to the saw. They simply deposit, what is probably basically creosote on the piston dome, and on the top of the combustion chamber. That was the discolouration that let them know that the filter was letting stuff get through. That, and the presence of fines where they shouldn't have been in the induction area of the saw.
Are fines good for a saw? Uhhhh... no!! Do they cause catastrophic failure? I sincerely doubt it.

I sadly must admit that fines were not the problem. The sawdust that was on the outside of the saw around the spark plug was unfiltered stuff, and I would guess some were more than 1/8" long. Though I brushed the area, I should have used compressed air to do a better job of cleaning. Expensive mistake on my part!

 

[Hermio]

We need to know a back story, like what caused you to change the plug?
Was the saw getting hard to start and you decided a new plug might be the answer?
Photos of the piston, old plug, new plug would be handy to back up your claims.

I just thought it was time to change the plug after about 10 years. The old plug did not look too bad, but once I had it out, I figured I might as well install the new plug. I did not take pictures, and neither did the dealer.