How do you "tune up" a hard-to-start Craftsman 18" chainsaw

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On Fri, 27 Aug 2010 12:04:56 -0700 (PDT), zzyzzx wrote:

You're joking right?
CORDED: The reason a chain saw can't use a power cord is that it would need to be hundreds upon hundreds of feet long and would be impossible to drag through the chaparral without catching on scores of bushes, rocks, and trees.
BATTERY: The reason a chain saw can't use a battery is that it would die after felling only a few trees and cutting up the limbs. We'd spend more time waiting for it to charge than cutting.
FOUR STROKE: The reason most chain saws aren't four strokes, as far as I can tell, is that four strokes without oil pumps can't be placed in all the positions that a chain saw needs to be without spilling oil into the cylinder.
TWO STROKE: The reason most chain saws are two strokes, I presume, is that is less expensive than a oil-pump driven four stroke and the two stroke works in any position.
BTW, if there are good four-stroke chain saws on the market, let me know which you prefer.
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http://www.youtube.com/watch?v=q1D4IdO28JU

nb
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CORDED: The reason a chain saw can't use a power cord is that it would need to be hundreds upon hundreds of feet long and would be impossible to drag through the chaparral without catching on scores of bushes, rocks, and trees.
CY: Even with a portable generator, still not really convenient.
BATTERY: The reason a chain saw can't use a battery is that it would die after felling only a few trees and cutting up the limbs. We'd spend more time waiting for it to charge than cutting.
CY: Need the new Nuclear Power Batteries. They are sold out of North Korea, on Ebay. Don't want the Iranian Nuclear Power Batteries, they sometimes explode.
FOUR STROKE: The reason most chain saws aren't four strokes, as far as I can tell, is that four strokes without oil pumps can't be placed in all the positions that a chain saw needs to be without spilling oil into the cylinder.
CY: And they are heavier. The used to be made, for felling trees. When one knows the saw operation is always going to be in the same position. They were operated by two men.
TWO STROKE: The reason most chain saws are two strokes, I presume, is that is less expensive than a oil-pump driven four stroke and the two stroke works in any position.
CY: Also, the two stroke fires on every piston stroke, so the HP to weight ratio is much higher.
BTW, if there are good four-stroke chain saws on the market, let me know which you prefer.
CY: I havn't looked, but they are likely out of the home owner price range.
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On Sun, 29 Aug 2010 11:25:42 -0700, SF Man wrote:

Gas turbine is the way to go... ;-)
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STROKE:

Where weight counts, as in a chainsaw, the two stroke cycle gives you power on every stroke where the 4 stroke cycle is only on every other stroke. That is really why. But to make a "run in any position" four stroke would increase the complexity.
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On Mon, 18 Oct 2010 09:12:57 -0700, Smitty Two

The poster confused me a little (nothing permanent).
The lobe on the crank/cam still needs to turn four times... thus four strokes.
I've always called it: intake, compression, power and exhaust. Counting combustion the same as the power stroke.
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wrote:

Am I mistaken, or does a "four stroke" fire on every other rotation? The ignition spark powers the crank down from a few degrees BTDC for power with all valves closed, and the upcoming piston pushes out the exhaust with the exhaust valve open. When it reaches TDC, the downward traveling piston sucks in gas through the open/opening intake valve, and when it reaches its designated firing degree BTDC, it fires. Every other stroke.
With a two stroke, the spark plug fires every rotation, with the intake and exhaust being achieved by a porting system routing gas and exhaust on different sides of the piston.
Class?
Class?
Steve
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You're all mistaken.
A "four stroke" is a teenage boy. That's how many strokes it takes him to "fire" when viewing online female-anatomical matter.
--
Tegger

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Tegger ( snipped-for-privacy@example.com) writes:

Doesn't a teenage boy become a "two stroke", and a teenage girl a "four stroke", when coupled?

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Of course, the same term can refer to different meanings. I think your meaning is also correct.
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Yeah, that is what Cuhulin was talking about with his 6 stroke situation.. It gets that way when you get old.
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On Mon, 18 Oct 2010 15:14:49 -0700, "Steve B"

The spark ignition happens at the top of the compression stroke TDC (valves closed). When fuel/air is compressed and fired piston drops to BDC ready for the exhaust stroke (valves open). No?

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.

No. Spark happens, piston travels to bottom, on the upstroke, the exhaust valve opens, piston comes up, pushes out spent gas, at TDC, intake valve opens, piston drops pulling in air, comes up on compression stroke, and a few degrees BTDC, fires again. One spark per two full revolutions of crank.
Steve
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On Mon, 18 Oct 2010 20:52:05 -0700, "Steve B"

The four strokes of a four stroke engine in living ASCII art
http://www.repairfaq.org/samnew/lmfaq/lmtfsofse.htm
I still call the compression stroke the power stroke --even if firing at BTDC or TDC. I think we get it.
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Thanks for the link, that's fun.
If you want to talk with other mechanics, it would be wise to call the compression and power strokes different things. The compression stroke is the one before the power stroke.
Intake Compression Power Exhaust
(in that order)
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Maybe.. You still get twice as many power strokes with a two stroke cycle engine as you do with a four stroke cycle engine, RPM being the same.
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Worth noting. There are actually two sparks, per fire. One spark is at TDC when the gasses are compressed. The second spark is also at TDC at the end of the exhaust stroke. The second spark is wasted, but does no damage.
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"Steve B" ( snipped-for-privacy@hotmail.com) writes:

Simple small four stroke engines (lawnmowers etc.) spark every crank revolution. The spark is usually triggered by the crankshaft on small four stroke engines. Larger four stroke engines (automobiles) spark every second crank revolution per cylinder. The spark is usually triggered by the camshaft on large four stroke engines. The camshaft rotates at half the speed of the crankshaft.

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Four stroke fires, every second rotation of the crank shaft. You described it pretty much the way I was taught. Same with your description of two stroke.
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The engines I've serviced, the camshaft rotates once for each rotation of the crank shaft. A "stroke" is the motion of the piston, either up or down. I think the confusion may be lingering.
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