Running a saw out of gas

Tom Dunlap

Tom Dunlap

Here from the beginning
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Retired in Minneapolis
There's a thread on AS that I responded to that should go on here too.

Someone asked about running a saw out of fuel. My SOP is to keep a mental note of how long I've been cutting. At an good time I'll stop and service the saw before it needs refueling. There is a very distinctive gurgle or stall that tells me that the saw is sucking an air bubble. Anyone who has run saws knows that sound. It is the yellow light warning you to stop now. On very rare occasions I might jiggle the saw to make sure that the fuel pickup is at the bottom of the tank and not hanging up on a knob inside the tank. The only time I would do this is to finish a critical cut. Otherwise the saw is stopped and serviced.

Here is a case study:


A number of years ago I talked with a friend who worked for a log home building company. The crew was burning up a lot of saws so they called the regional Stihl distributor. The tech came out to the place where they built the log houses.

After watching them work for a while he figured out the problem. The workers would be cutting and the saw would gurgle when it was low on gas. Instead of stopping to refuel they would jiggle the last drops of fuel towards the pickup and get the last cut done. When the saw sucked up the last drops it would go lean because it was pulling vapors or only drops of gas. After running the saws many times in this leaned out mode the saw would overheat and destroy itself.

After learning this the work procedures were changed. At the first burble of low fuel the saw was stopped and serviced. After the change they stopped burning up saws.
 
Yeah fill before it get to run on 'fumes'. Especially when you have a filty airbox. I have lost one 066 in mid summer felling london plane and the airbox was full that 'leave-hairs' and in one jingle it got fried on a empty tank. I never noticed anything the tank got empty, it just stopped. I refilled and couldnt get the crank round again. After a few minutes it came loose but never started again..... I usually know how many trees i can fell and prune before its empty. I will check the gas after some trees, thats i like those stihl tanks so much.
 
Interesting--I've gotten into the habit of refilling at the first warning, just for convenience, but never realized the potential for damage. Does this mean I should stop running my saws dry before extended storage (extended usually means a month or two, tho my gas drill gets used pretty rarely)?

k
 
I've never realized the potential for damage, either.

Thanks for the schooling!
 
The advice I've gotten for storage is to:

WArm up the motor
Stop the motor :)
Dump out as much fuel as possible
Start motor and let it run AT IDLE until it quits

Over-reving leads to overheating.
 
It's not just the fact that they get a bit hot,but the lubrication is in the gas/oil mix.A lean out condition causes the temp to rise very high in the cylinder.It burns what is left of the oil film from the cylinders and oops.Not a big deal,in an idle condition,as Tom mentioned.Think about it,a saw engine cranken on at 13 thou and you shut off the oil,ugh.
If you loose lube to a bearing,at that speed it can cause
the hard as a rock bearing to start to spall the outer edges of the balls,or rollers.In a given about of time the bearing will fail and the engine will come apart like a dollar watch,or tie up like a bulls rear at fly time.
Another way to look at it is that in an idle conditon,when the saw hiccups,it basicaly dies.However at speed the inertia carries it over so it fires every so often,with a lean out condition the whole time.
 
The Stihl manual for my bruscutter says to always leave the saw fueled up at the end of work.
I understand that unleaded fuel absorbs water more readily and goes off faster than leaded.
You guys are on unleaded in the States aren't you?
A local motor mechanic who teaches fuel injection techs. says for any fuel injected vehicle keep it as full as possible all the time. In Winter that means less water in the system from condensation and in summer it means less heating up of the fuel pump as there's always an excess of fuel pumped to the engine which goes round and round through the pump, he reckons.
Pete
 
Yes, for an engine which sees reasonable usage you should keep the fuel tank as full as possible all the time, but long-term storage is a different animal. The saws come from the factory essentially idled dry.
 
Good word on running saws dry, I tried to finish limbing a tree once at the end of the tank on an 046, and melted the piston. Not a good idea. Live and learn.

As to the winter storage issue: don't leave gas in your saw over the winter. Saw mix seperates and will not mix together again after 6 weeks. Then your tank looks stupid because the seperated oil stains it. (mostly a problem with Stihls) Idle it dry. I have to purge saws for airplane flight regularly, and idling them dry has never caused a problem.
 
What type of saws are you guys that are burning em up running? I not disputing your research but we run em completely out multiple times every day all week and I have only ever seen couple sieze up or burn out. One of those was because of a ripped boot.
I work and beat the piss outta my own saws and I have yet to lose one. You gotta give em a breather ever few seconds or so.....holding em full bore will cook em. One of teh most important thing about running a saw effectively is the ability to listen to it.
If mine sit for any lenth of time i pull the plug and drip in a little 2 stroke oil before i start the bugger.
 
Logging I would run a saw out at least a few times a week. Not like revving it on fumes but never saw ill effects on modded 660's. Burning 6+ tanks a day you wear a saw flat out in a year. The carb always goes long before the piston/cylinder.
 
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