Stihl 025 Chain Saw debugging

I think you mean won't fire....

seconds like it was going to start.

Meaning it fired a few times?

If you're not sure if it's firing, first thing I'd do is see if it has spark. You can do that by taking the sparkplug out, then connecting it back up to the ignition wire and seeing if it sparks when you pull the cord. You may need some jumpers to hook it up to make it convenient to do the test.

If it is firing or it passes the above test, then the carb is the next suspect. They can foul pretty easily, especially with gas with ethanol in it. The fuel line is a possibility too, they can crack with age. You probably need to pull the carb to be able to check the fuel line. Carb can be disassembled and cleaned. Also it probably has a fuel filter, which may be inside the gas tank on the end of a hose and can be gotten out by snagging it with a clothes hanger.

Finally, there are the more profound problems, depending on the age and how much it's been used. Anything from compression to bad crankcase seals. The latter causes erratic performance, hard starting, rough idling, etc.

seconds like it was going to start.

If the saw actually fired a few time, then it is probably not the on- off switch, but douvle-check to make sure. Then go buy a spray can of starting fluid.

Is the saw a 2-cycle? Maybe you forgot to mix in oil with the gas the last time it was used and with no oil, the compression is shot to hell and that's why it won't start.

After all that, might be flooded. My Homelite used to do that. I'd have to pull the spark plug out, yank the start cord a couple times, and then put the spark plug back in.

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1. Replaced the old gas. Won't start at all.
2. Blew a bit of carb cleaner into the piston. Won't even spark.
3. Replaced the spark plug (figured I fouled it) turned over for about 2 seconds like it was going to start.
4. Blew a bit of carb cleaner into the piston. Nothing.
5. Remove the air filter, blew some carb cleaner into the carb. Nothing.
6. Had a beer or three, helped me not the saw.

Can someone help me with the usual suspects?

I have fairly new gas. Made sure I had plenty of bar oil. I replaced the plug. I've tried having it in both choke position and normal run. Made sure the chain break wasn't on :-)

Thanks.

Since the saw "almost" started, it's likely a fuel mixture problem. That's my guess.

Have you ever heard of a four stroke chain saw? I have, saw a picture of one. Had about a 48 inch bar, and took two men to hold it (one on each end of the bar).

Aren't most consumer model saws two stroke? Like boat engines?

Only time I can think of, a two cycle run on straight gas. Locked up tight. It was a moped, and the owner had to take it in to a repair shop to get it freed up.

Christopher A. Young Learn more about Jesus

If the saw actually fired a few time, then it is probably not the on-off switch, but douvle- check to make sure. Then go buy a spray can of starting fluid.

Is the saw a 2-cycle? Maybe you forgot to mix in oil with the gas the last time it was used and with no oil, the compression is shot to hell and that's why it won't start.

I showed my late friend GB how to test the output of the ignition on his chainsaw and it freaked him out. I took the air hose from his shop compressor and using the rubber tip on the air gun which I stuck into the open spark plug hole pressurizing the cylinder. I told him to pull the starter cord and the little two stroke engine ran off the compressed air. The bright spark off the spark plug wire showed it was good. ^_^

TDD

I've wondered if it's possible to spin a lawn mower engine with electric motor, and use it as an air compressor. I've never tried it, but I'm guessing it is. Cut the exhaust valve shaft back, so all the compression goes out the spark plug hole, through a check valve.

Christopher A. Young Learn more about Jesus

I showed my late friend GB how to test the output of the ignition on his chainsaw and it freaked him out. I took the air hose from his shop compressor and using the rubber tip on the air gun which I stuck into the open spark plug hole pressurizing the cylinder. I told him to pull the starter cord and the little two stroke engine ran off the compressed air. The bright spark off the spark plug wire showed it was good. ^_^

TDD

Brand new plug, unless I managed to flood and foul it, there is no spark.

Just to make sure there is no "kill" switch on this right (meaning I won't get a spark.

1. Should I have the saw in choke or stop when I test the plug?
2. The removed plug can't reach any metal, I am just using a wire from the plug to the outside of the engine, that is a valid test right?

Thanks.

t get a spark.

e plug to the outside of the engine, that is a valid test right?

It doesn't matter if the choke is on or not. But the saw should not be on "stop" because that would seem to be a selection where you would not want ignition, no?

Just go through the normal starting procedure with the spark plug out. You want the ignition wire connected to the plug and a ground path from the plug back to the engine metal. Like it would normally have if it was screwed in. Could use a jumper with large aligator connectors or even an auto jumper cable. Or you could wrap a bare copper wire tightly around the plug threads and use a jumper of some kind to connect it to the engine metal. I'd do it somewhere where it's partially dark, like a garage with the doors closed, so it's easy to see. With the plug out and no compression, the engine will spin easily and you should see a spark at the plug gap.