Causes of Saw Failure

[a. palmer jr.]

Straight gassing is not an issue 'you' have to deal with. For the years I've been an AS member not once has an op said 'he' straight gassed a saw. Its always the neighbour, distant uncle, odd guy who gave me this saw etc. So it's always someone else and YOU never have to worry about the issue.

It's easy to not straight gas a saw. I just don't keep any straight gas in the same place as I do the mixed fuel. In fact I keep two kinds of mixed fuel around, the gasoline/oil for the saws and the ethanol/oil for the lawn mowers. I'd use the saw mix in the Lawn Boys but they use so much fuel that it gets kinda expensive.

 

[Boomer 87]

I'll add to the list losing your saw from the back of your truck while at highway speeds.[/QUOTE


Years ago I lost my 93 Yamaha blaster out of the back of my truck at highway speed......... not a good deal

 

[svk]

Years ago I lost my 93 Yamaha blaster out of the back of my truck at highway speed......... not a good deal

My dad's friend had an old convert a ball (the kind that had the threaded sequence versus pin) and was pulling our then new Honda atv. It went off into the woods luckily not in town. Wheeler drove after the fact but both that and trailer were considered totaled.

 

[Boomer 87]

My dad's friend had an old convert a ball (the kind that had the threaded sequence versus pin) and was pulling our then new Honda atv. It went off into the woods luckily not in town. Wheeler drove after the fact but both that and trailer were considered totaled.

It's a sinking feeling to look in the rear view and see your fourwheeler barrel rolling down the highway. No wonder the car behind me backed way off lol

 

[merc_man]

Hasn't happened to me, yet (knock on wood) but it could still easily happen. You are mixing gas and someone calls or stops by, you grab the wrong can, etc.

I'm sure more than a few AS members have done this but won't own up.

I came close once to straight gassin a saw. Usually pour my mix before put gas in can and never did the one time. Couple days later went to put gas in saw and seen it wast blue from oil. Glad i caught that.

 

[ssm1699]

The only way I would be able to straight gas my equipment is if I didn't mix the fuel. The only straight gas that I have, is in a 5 gallon can. My mixed fuels are in 2 1/2 gallon cans and there is a diff in the cans, so I know which is mixed at what ratio. The most damage I have ever seen to a chainsaw has just been minor scoring on the exhaust side. My guess was that it got heated a bit. The piston and cylinder are salvageable though. Probably just needs a set of rings because of age.

 

[foeke]

A brother/wife/neigbour mixed 4t instead of 2t oil. Apparently that works the same as straight gas. It was my first chainsaw . A hard lesson wich benefited my later saws. The dealer didn't get is since the colour was just right. That gave me the clue it might be the novice user's fault (again not mine of course) so I backtraced what happend and saw no garden appliance on the bottle of oil wich someone bought in a german tankstation not actually speaking german. Then I noticed the 4T. . . I still wonder if I would be as happy with my second hand makita 50cc as I am still after 5 years with my then new husky 353. The bottle of distruction was ritually burned to death. Never had an other failure of any kind other then trees falling on them.

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[naturelover]

Grandpa lost his Honda ATV out of the back of his truck long years ago, but luckily it landed on all four wheels and glided harmlessly to the side of the road.


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[ken morgan]

I'll add to the list losing your saw from the back of your truck while at highway speeds.

that had to be a pisser.

 

[Steph79]

Thanks for all the input, I try to follow 50:1 as per the manual but I keep the mix a little oil rich by filling up the gas can to a point just a little below the fill line. I imagine there's a bit of give in the guidelines because I don't think most people are using syringes or anything to get the ratios bang on, the manufacturers must realize how most people do their mixing. My father-in-law mixes the gas and oil right in the gas tank of the saw, don't ask me how but it seems to work and he's been doing that a long time.

I also have 32:1 in the garage for the lawn boy and straight gas for the a few other things. I've actually listed both the mix and the equipment it's to be used with on all the gas cans, just for my own benefit I guess, I'm the only one who ever runs any of the equipment.

I get a little paranoid when I here all the saw failure stories on these forums where it doesn't sound like anybody was doing anything out of the ordinary. Probably when I get a few more hours on the new saw I'll stop thinking about it. I used it a few hours in the heat the other day and I thought I heard the engine noise changing every once in a while, more of a high pitch sound would come and go. Could have been my imagination, also could have been my ear muffs moving around, got me over thinking things probably.

 

[Steph79]

What about on the technique side a little? If I do one or two big cuts I try to mix in a few smaller cuts to let the saw rest, if I hit a hard knot I try to back off a little and change my approach angle, same if the saw seems to bog down a bit I back off it. I also try to let the saw do the cutting and not put too much extra pressure to force it along, that's something I was taught early on with power tools in general, "let the tool do the work".

Anything else I should be thinking of?

 

[a. palmer jr.]

What about on the technique side a little? If I do one or two big cuts I try to mix in a few smaller cuts to let the saw rest, if I hit a hard knot I try to back off a little and change my approach angle, same if the saw seems to bog down a bit I back off it. I also try to let the saw do the cutting and not put too much extra pressure to force it along, that's something I was taught early on with power tools in general, "let the tool do the work".

Anything else I should be thinking of?

Probably why so many saws come in here with a mushroomed bar, people pushing down on the saw because of a dull chain..

 

[Steph79]

Probably why so many saws come in here with a mushroomed bar, people pushing down on the saw because of a dull chain..

Learned that one when from an electrician I worked with, he could tell just from watching me that the drill bits I was using were dull from the force I was putting on the drill, also I used to never be able to keep a straight line with a jigsaw because I kept trying to force it through whatever I was cutting to get done faster.

My work got a lot better when I slacked off a little, it was also easier and I don't think it took any longer.

 

[Chris-PA]

Not necessarily... Two strokes require *more* fuel to make power at a lower RPM under load. The main thing is that the 4-stroke goes away when under load.

Found this out with a weedeater with a string head (under load). Set the carb high screw to maximum RPM (power) with the normal string length. Then lengthened the string slightly which increased the load and lowered the RPM. I then found that I had to richen the HS screw to to get the maximum RPM (power) with the new, longer, string length. A saw should work the same way but it is not easy to measure.

The load of a string trimmer head is much different than the load of a chainsaw. The spinning trimmer head is like a "brick wall" load where the engine cannot spin it past a certain rpm, especially for the smaller engines on trimmers. A saw chain is a more linear load - if you lift the rpm will be limited more by the terminally rich mixture of the carb and the properties of the engine.

But they use the same kinds of carbs with the same fuel mixture vs. air velocity defect, where the mixture gets richer with increasing rpm and leaner with decreasing rpm.

By lengthening the string you lowered the rpm where the load starts to overwhelm the engine, and that leaned the mixture out because of the way these carbs work. So it's not that 2-strokes need to be set rich to make more power down low, rather that your mixture leaned out becasue the running rpm dropped. The correct mixture still makes more power than an over rich one.

 

[motorman1]

No idea about how to adjust string trimmers under load, but I have some experience with chainsaws and know one needs to set them, via tach, to the prescribed limits, for best results / longevity. Some use "two-stroking" to set them, I do not. I prefer the same method the dealerships and Bailey's takes, the "safe" numbers. I have never had a failure yet. Might have left a bit on the "table", but have not had any failures in more than 5+ years, so I count that as proof my system is working.