Engine Temperature: When is hot too hot?

John Vander

I want to know more about engine temperature. Here in Japan, the summers get helll-hot with a lot of humidity, and my machines seem to get pretty hot after working for a short while. I rotate my machines and also allow them to run for a little while after a long job. (I know that sudden cooling is no good.) I use small sized saws since they are easier to get into the mountains with. Also, trees available for firewood are relatively small, so using huge machines is overkill. Any suggestions on how I can monitor the heat of the engine?

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rogue60

I dont know about other saws but stihl saws ive never had a problem with them over heating, its work the guts out of them as normal no matter how hot it gets...but im sure crap quality two stroke oil and lean mixes would see a seized saw...

Eric Frei

I'd say use low octane fuel too.... but not any E10 etc

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olyman

my take.....in the summer,,even tho ambient is warmer,,how much is warmer??? serious.....as the diff,,is at what most?? 80 degs???? how hot,,is a chainsaw running,,and how much difference does the saw know,,in 80 degrees diff??? not harshing you at all,,as ive had my saws get warmer also..and the problem i run into,,is boiling of fuel.....that being said,,as eric refered to,,is eth will boil much easier,,than gas!!! eth!!! dang!! but,,ive often wondered,,why the fins on the flywheel,,arent set as such,,to near blow the fins off of the cyl??? i mean,,how much air,,is too much???? and when my fuel boils,,i just set it down,,with the cap up,,unscrew cap,,and let it boil off,,and cool down a bit..im of the opinion,,that with a chainsaw,,in a milling fixture,,THATS creating much heat!!!!!!!!!!!!! and a guy on a forum that eric knows of[Bob in aust],says he lets the saw cool down for awhile after every cut in a log....if a cut takes 10 minutes tho,,id believe that that saw,,has reached the stratosphere so far as cyl heat,,in much less than 10 minutes!!! and the damage would happen way quicker also..to tell the truth,,i keep the oil mix in my saws,,at 32:1,,for that very reason..it gives a extra bit of protection window....and some of my saws..wont boil!!! i believe it to be enough diff in design,,that it stops boiling...thats my take,,your mileage may vary..

sun64

I have a question about chainsaw engine temperatures.
Can anyone enlighten me on why some chainsaws will fire up all day long and some others wont once they get hot.
I live in Darwin , Australia where it is usually 34 to 39 degrees celcius
What type of fuel is best for chainsaws in Australia. I usually buy the higher octane rating but have not checked if it has ethanol in it or not. I used to run a higher ratio of oil as well but was advised by the Husquvarna dealer just to run to standard specs.
Is it a vapour lock thing or spark plug / ignition coil overheating. Is there a way to check or eliminate the problem or is it a part of this enviroment.
I have owned and used Stihls, Husqvarna's, Poulan, Mc Culloch saws over the years. Some of the cheaper saws have worked as well as the more expensive saws.
My friend has a Husky 3210XP which does the same thing when it is hot.
Nothing worse up here when it is bloody hot, you just wont to finish off the job and the saw wont start because it is hot.
sun64

John Vander

Thanx for the advice guys. Maybe I'm just too nervous about how much pressure I put on my machines, but I'll make sure about not overdoing it. As far as temp. in Japan is concerned, it gets about 37deg.C where I live, but the humidity goes up to about 80%! This retards cooling time tremendously, and did I mention that you sweat like a pig? By the way, I use Stihl two stroke oil and I mix it standard 50:1.

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sharkey

32:1 fellas especially when milling. At 100F air temp the exhaust temp can hit 500F under a long load. Cylinder temps can get up to 300F. The oil is all that is between the cylinder and the piston, so use the best synthetic you can find. If your curious what temp your running, get yourself a small infrared heat gun at one of the radio controlled hobby shops.

Eric Frei

I know exactly where you are coming from.

The other day I went to fire up another blokes Shindaiwa, no chance, headed for the Stihl. But it can happen with Stihls too.

I reckon it happens when you are at that temperature that is between a choked start and a normal start. Screw it up and you might flood the saw.

Change you spark plug out first, they get dodgy I find. But some saws can suck and once flooded, forget it.

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sun64

Thanks Eric, I have purchased new NGK spark plugs. Have not fitted them yet.
I also reckon I was using the fuel with Ethanol in it which may have had something to do with it playing up when hot.
I may up the oil ratio a bit as I believe with hotter temps up here it wont hurt with a little bit more oil to fuel ratio just to give the engine a little bit more protection.
Darwin NT is a harsh enviroment , a lot hotter than where Stihl's and Husky's are made. Our old Commodore was a prime example as the Hood lining fell off and the rear windows leaked . The vehicle was working in an enviroment hotter than from where it was made and designed.
Anyway thanks Eric, will play around and see how I get on.
sun64

olyman

what sharkey said above,,and what i refered to also..milling pulls any saw hard..and that little bit of oil,,is your only protection...running 50:1,,is running on the ragged edge...a bit more smoke, at 32:1,,so what??? beats melting the engine down....

rogue60

To keep cost down we run mineral based oil at 25:1 we have five 660's and a few 88,s. At times they can all be running all day so yes thats heaps of fuel,we have never had a saw seize or over heat...with synthetic oil we run 32:1 and we only use castrol oil...50:1 will see the life of the saw plummet, of course husky and stihl dealer's tell you to run 50:1 they know you will be back in no time for a new saw lol.....My mate bought a yamaha two stroke out board boat motor the sale rep and the manual say run it at 100:1 crazy!!! they even told him that they have had a few back seized already,but said still run 100:1 to him ..

sun64

Thanks guys for all of the advice, it is much appreciated and we have all benifited from other peoples experiences and information, that is why i truly appreciate the advice from fellow enthusiasts likeminded.

Eric Frei

I also run around 32:1 Stihl two stroke oil.

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Tony Knight

Same

Brent Ferris

I have run Husqvarna and Stihl on hot days 35-40 C. Saw gets so hot, adding more gas, boils in the tank, start it up and run again. Have in the past done this for 3-5 hours flat out. HEat is no problem. Saws can take a lot more than you or I can.
Run saws at 40:1 - dealer oil. Always use premium octane, no ethanol. My smallest Stihls I don't run as long 1-2 gas tanks max at a time and they are min 20 years old. Have never replaced the cylinders., Humidity is high in Toronto in the summer - 70% humidity is low.
THe problem with your saw not running suggests vapour lock -- some saws have better ventilation. If it is thru the cap, maybe hole is too small, or is plugged,

15 years or so ago, the Husky dealer recommend 100:1 with synthetic oil, but I found the saws needed more repairs - not from seizing, but parts wore faster. 40:1 is richer than recommended but repairs are a lot less frequent.

I will try the 25:1 mix next time I am milling wood - milling does give a saw a beating.

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Done it

I've always run 25.1 Castrol 2T and low octane, no problems and it gets hot here.

We did have an oil thread if anyone is interested.
The dreaded chainsaws oil thread

Eric Frei

10 years ago. Was a real hot day, perhaps 38C one summer @ 2pm.

Sawing up log, tank after tank, 22" bar on MS460 (saw was 6 months old). Using 32:1 Stihl oil and ordinary unleaded.

The saw went from flat out to an eerie dead stop in 0 seconds flat. It would not crank, it was seized. Took out the plug and saw a mess inside.

Dealer strips saw whilst I watch.

Fuel checked OK, oil checked OK, problem is not that nor operator.

Bad news.

Stihl at the time only has 3 month commercial warranty, dealer goes into bat for me, Stihl says send saw down to Melbourne to check it out.

Stihl repair saw and technician contacts me, freak occurrence they say, "one of those things". Saw returned after 6 weeks rebuilt. I got another 9 years out of that saw.

What happened:- A piece of piston ring failed and jammed between the top of the piston and the exhaust port. Beside making a mess of the piston and jug it bent the conrod and snapped the crankshaft.

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sun64

Thanks treeshaveneeds,
I have found this a problem on a lawn mower before where the vent hole was blocked. Put up with it for years before I found out what was wrong and why it would'nt go when hot.
Some chainsaws vent through the cap and some through a vent tube and cap under the engine cover.
I have played around with the vent tube and cap. I will have a look at it again when I put in a better quality spark plug and change my fuel from the ethanol blend I believe I had used and see how it goes.
If not then i may use a small piece of silver building roof insulation and placi it under/ around the coil as a heat sheild.
I have done similar things like this before on other gear as it helps improve the life of the item. I have covered the side of the ride on mower battery , fuel lines on my vehicles in the engine compartment etc .
A mate of mine told me he new of a guy who moved the fuel lines on a Holden Jackeroo 4 x 4 as they went straight past the cylinder head and heated up the fuel. He got a lot better fuel economy after that.
As i stated before a lot of gear is designed in colder countries and when running up here in 39 degrees celcius and up to 98 % humidity in the build up and wet season, it puts some gear to the test and can shorten their life span.

sun64

John Vander

You all got me convinced. I'll change the oil mix ratio on my saws. Thanx guys.

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KevinE

The overheating thing happened to my little Makita 231T yesterday It was hot here yesterday & I was taking out a massive "dwarf" umbrella tree that had gone feral in someone's front yard. Couldn't get my vehicle into the yard, so all the green had to be tossed over a low fence (shit of a job). This thing had more branches growing in more directions than I have a hope of describing Anyway, the light weight of the 231T was perfect, as I was going to be cutting branches for 8 hours straight (cut them off the tree & then cut them to fit into my trailer). The saw ran for 2 hours or so, then started to misfire, stall, refuse to restart etc I cleaned the plug, nothing, manually vented the fuel tank, ditto! So I spent the next 6 hours hanging onto the heavier Echo 350T At the end of the day I pulled the starter on the Makita (which had been resting in the shade for 6 hours) & it ran like a champ. This happened the other day when it was hot too & the next day it was fine. Time to test the 12 month Makita warranty me thinks!

John Vander

I have a small Makita 333. Even though a carpenter's saw, that thing doesn't give in!

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Paul Toivonen

What kills most saws is so simple it is often overlooked.
A blocked air cleaner.
Hedge trimmers are the worst for it. Some I have had block up and stop running in a couple of minutes.
If you clean your saws every day and check them so often ,should be OK.
I run about 40:1 2T.
It works out like that the, way I make a mix and I have seen saws cooked on 50:1.

OldNick

Not trying to start an argument, but this may be important. I don't think humidity will affect engine cooling, and it may even help a bit. I would assume that wind would help, as it would move air over the saw, although many (all?) have a fan tied to the crank anyway.

Humidity and still air affect the human _body's_ cooling because the sweat cannot evaporate to cool you. So you get a double whammy. The sweat can't evaporate, so the body sweats more trying to make it all work.

Nick

John Vander

Good point there. As far as humidity is concerned, I find it hard to keep stuff from rusting. I know some guys take out the spark plug when storing their machines, but frankly I'm wouldn't want to do that here.

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OldNick

Yeah I can imagine. I read about camera lenses gert6ting fungus on them in humid conditions. That would really tear me up.

Nick

John Vander

A lot of my leather stuff has suffered too. MOLD!

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