saws with mind of their own

cory

Tree House enthusiast
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Had a balls to the wall job today made wallsier due to saws that don't like the sudden onset of warm temps. It was about 80* today, first warm day of the year, and as the day wore on , Husky 572 which is normally a ripper of a saw, got wicked hard to start, vapor lock multiple times and I wanted to give it a little smesh. And if memory serves, it seems to happen every year like this- sudden warmth early in season, saw goes nuts, later in season saw is fine.

What gives?

@Nutball ?
 
Autotune issue where the heat confuses it? That doesn't seem right, but it's the only variable I can think of. I'm assuming you go through gas in a timely fashion, so it isn't old gas getting weird in the heat.

I was milling today wondering why I was feeling so much heat in my face. Unrelated, I took the cover off to check the air filter, and noticed my shutter was in the winter position. 80° today. Doh!
 
Either the winter blend fuel is boiling, or autotune needs to reset.

Let it idle for 3min straight to set the idle, and make a 40 second long continuous full throttle cut down the length of a log.

It helps to learn how to shut off a finicky saw to help the chances of an easier restart.

Really, the changes in weather should mess up how any saw runs, but autotune is supposed to help solve that problem for you. The problem is that it is not easy to make a simple computer do a perfect job of keeping the saw in tune without having temp/pressure sensors, and fuel type sensor, and or an exhaust sensor, and have it calibrated to stay in perfect tune under any condition.

Running half throttle a lot can mess it up too, until you go back to just full throttle through everything.
 
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  • #4
It helps to learn how to shut off a finicky saw to help the chances of an easier restart.
Good info, thx.

What is this saw shut off voodoo?
 
If I know a saw is prone to vapor lock or start lean when hot, I may choose to choke it off, even going as far as revving it up all the way before choking it off to prime the engine full of gas (I do this with a certain ms180 in the summer). Then, while it is working through the flooded condition I left it in, it is able to work through the vapor lock or whatever is causing the lean condition. You have to be careful doing stuff like that, because it can make starting really hard if you get it wrong.

I remember experimenting with different shutdown techniques with my 572 while milling in 35-65 degree weather, because sometimes it was hard to restart. Not really that hard, but 5 or so pulls when warm, trying different things with the choke, rather than just 1 pull. If I remember correctly, I'd choke it off at idle, then for restarting I set the fast idle, but with the choke off. For the most part it worked for my particular case. It's good practice to let the saw idle for a while, like 30 seconds or so, before shutting it off to let the engine cool while fuel is still flowing, so it doesn't heat soak the carb causing vapor lock. Heat soak in an autotune could cause the temp sensor in the carb (I think there is one) to get a false reading messing up the fuel mixture. Too much heat in that case should cause autotune to reduce fuel flow, meaning you may need to choke it when starting, but I could be wrong. I find it helps to let it fast idle for 5-10 seconds after starting, so it doesn't try to die right after starting.

The problem with an autotune feature is that when you try to learn to compensate for its shortcomings, autotune is also changing based on weather and running conditions, so it takes much longer to learn the quirks. That's why I like to have a fully adjustable choke, that doesn't release when the throttle is touched, so I can control the amount of fuel when starting.

It's also a good idea to keep an extra starter pulley or 2 on hand for the 572. They are not built as tough as they should be, and eventually break.
 
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  • #6
More good info, thx.

Some of that stuff I already do but I'll give the choke/kill a try. Warm again today and I was doing something I never do which is let it idle for a minute or two before needed for the next cut. Normally I always shut a saw down, after a bit of cooling with mid speed revs, if next cut will be 45 or more seconds away, thinking being is to discourage "carbon build up". Well, letting it idle does prevent the need to restart it!
 
... this "autotune" you speak of , after some experience I will never again own a saw with such ... sold off the ones that had it. Easier ...
 
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  • #8
They don't make chipless saws anymore, do they?

When that EMP hits, bust out the crosscut saw :headbang:
 
The old fashioned coils could be pretty susceptible to EMP, forget the chip. Coils are designed to generate electricity, so an EMP on a coil is asking for trouble. You could set aside some saws with the coils shorted and contained in a metal box if you are worried about having a working saw after an EMP.

Husqvarna 585, T525, and maybe the 565 are non autotune. And there's always the 365 and MS 382 from Asia. I don't think the 382 is mtronic yet.
 
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  • #11
Shit's getting crazy. Warm again today, 80*. Husky 572 acting up again but I didn't use it much today, used my main 201 which until this week is always a beast of a small saw. At one point, I couldnt get it started no matter what I did. That is a first. Got another, old 201 going to finish the job.

It's a problem when you cut wood for a living and your saws run poorly or not at all. With husky yesterday and 201 today, removed fuel cap and loads of fuel burst out, and then remaining fuel in tank bubbled for another 45 secs.
 
Must be the winter blend gas boiling. That would vapor lock the lines. At least the ms500i has a primer bulb specifically for purging vapor lock. Sometimes you have to gently push the bulb a time or 2 right after starting when the vapor lock is bad, so it doesn't stall.

I would look into some sort of additive or not fuel additive chemical that can be added to the fuel with no ill effects to increase the boiling point. Maybe canned fuel is the way to go until the summer fuel reaches the stations. Some tree companies only use canned fuel. I think there's a major gas retailer in PA that ships all kinds of 5-55gal drums of gas and racing fuels.
 
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  • #13
the 572 has a bulb, I guess it's a purge bulb, I played with it some, I'll try it some more.

Yeah I guess it must be the fuel since multiple saws are affected. I'll call the saw dealer, see if he has additives.
 
Premix would be better than trying to correct a batch of fuel. A dealer might not know much, and just try to sell you whatever they have.

You might just have to choke the saws off. There was a 100 or so degree day I was using the ms180 that vapor locks easily. It ran out of gas, and was still hot when I went to start it. I had to put gas on the air filter, and use my hand as a sort of choke to control how much gas vapor could get into the carb so it wouldn't stall from being too rich or lean until the vapor in the fuel line cleared. Pain in the butt, but it was the only option other than waiting a half hour for the saw to cool in the shade.

It's good to be smarter than the tools, so you can make it happen. Once I had a 10hp chipper/shredder I needed to use for a lot of work, but the float valve was solidly stuck from years of non use. So, I pulled the fuel line off the carb and stuck it in the venturi and adjusted the fuel shutoff valve until the right fuel mixture was achieved. It didn't run great because the governor couldn't control fuel flow, but it got the job done.
 
More good info, thx.

Some of that stuff I already do but I'll give the choke/kill a try. Warm again today and I was doing something I never do which is let it idle for a minute or two before needed for the next cut. Normally I always shut a saw down, after a bit of cooling with mid speed revs, if next cut will be 45 or more seconds away, thinking being is to discourage "carbon build up". Well, letting it idle does prevent the need to restart it!
When I bought my first Stihl MS462, it was the same way. Terribly hard to restart. Once I modified my behavior and just let it idle between cuts it was great.

The problem is that when you shut off a saw, there is no longer any cooling air blowing over the engine to keep it cool. Everything begins to cook in its own heat. The carb gets hot and the fuel in it vaporizes. If the saw has a purge, pump the purge until you feel all fuel in it and no air. Then one pull on choke and second pull without choke.
 
Lot of truth to that .Some can take the heat from a shut down and some will fail on a restart .My worst to get started which is also my fastest,a Husky 2100 CD .To make matters worse those things are like rope starting a Harley .Some for example the old Stihl 038 Mag was often said to be the "hot weather " saw .They seldom fail .As for the modern saws I know nothing about them and rather doubt I ever will .
 
We were out on a crane rental yesterday and all the saws were acting up. 500i, 462, 441. Got back to the shop and one of the guys was trying to start his 500i and was getting really pissed off. Asked if anybody was having trouble with their saws, and everyone said they were. Love my 395XP, it just doesn't care.
 
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  • #21
I called the dealer, he said it's likely the gasoline. I went online and learned about summer gas and winter gas. Apparently the changeover is happening currently. If I still have problems monday I guess I'll have to buy some premixed.

Thx again for info, Nutball et al.
 
How much 2stroke fuel do you use cory? I'm wondering if it would be better just buying premixed all the time. Costs more, but it should be healthier to breathe, and fewer mystery issues with the saws.

Maybe there's a place close to you?


I paid $27 for 1.3G, which I don't think is bad. I haven't used it yet. It's my emergency supply if I run out of corn free gas.
 
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  • #23
I go thru approx 5 gal/week.

Premixed seems pricey but something's gotta give over here
 
Not advocating for high octane use in a saw as it’s not normally required, but you might try something up in the 95+ range just to see if the anti-boiling properties are better. At least for the next few weeks until they get switched back to summer fuel
 
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  • #25
I always use mid grade, on up from regular, not sure of it's octane tho
 

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