Home Forums Hunting & Shooting Hunter's Campfire For all you chainsaw mechanics out there

My son has a small chainsaw that starts okay, but after it runs for a little while it looses power and quits. If you let it rest for a while it does the same thing again. Is there a relief valve on the gas tank? Inquiring minds want to know!

Denny

Replace the gas cap.
The vent is plugged.

Either that or the rings are going out. Heats up and loses compression until it cools down.

What brand of saw is it?

I've had trouble with the fuel line where it goes to the carburetor not being tight enough on the barb and losing vaccum and not pulling enough fuel. Does the saw leave a spot of fuel if you leave it sitting?

Another thing,on a Stihl carb there is a small,super fine screen under the diaphragm that can get blockage...on my saw it is round,about the diameter of a pencil eraser

vent in cap, or fuel line degraded from ethenol blend would be my starting point

Another possibility if it is an old saw. The pickup in the gas tank has weight to it to follow the gas when the saw is at different positions. With the new gas containing ethanol/methanol the pickup hose looses it's stiffness. It can fold back on itself and cut the fuel off.

this

[quote=teamprairiedog]

What brand of saw is it?

I've had trouble with the fuel line where it goes to the carburetor not being tight enough on the barb and losing vaccum and not pulling enough fuel. Does the saw leave a spot of fuel if you leave it sitting?

Another thing,on a Stihl carb there is a small,super fine screen under the diaphragm that can get blockage...on

It is a Poulan (spelling) about 6 years old. It hasn't had much use.

I have never seen a vented gas cap on a saw,i have seen a hose with a bronze filter coming out of the tank.I have only used one poulan and the gas line was short from the factory so it ran out of gas with about a half left.

Yep, I'd inspect the fuel lines and fuel filter in the tank first. There's also a little filter screen on the carb.

Replace all of the lines.

I had to do that on 2 of mine.

Darn new crappy gas.

You got a damn good point there, come to think of it.



GTC

If the rings are really worn it would be hard to start but probably run a little better as it heats and the piston expands in the cold cylinder.

Sounds like it might be running rich. That works when the engine is cold/cool, but not so well after it warms up. You might check the air intake filter/screen since that being plugged might be acting somewhat like the choke. More likely, there is some gunk in the carb that prevents proper passage of air and fuel. (This sounds similar to what can happen when the saw gets some ice in it...which, of course, is an easier fix.)

Sometimes 2 strokes will act like that when the crank seals are going out. I had a boat motor that would start and run perfect until it heated up.

Also check to see the 'spark arrestor' screen isn't plug. Most any saw less than 25 or so yrs old will have one, located in the muffler. If the screen gets plugged it will give the symptoms you describe. This is an easy check.

Some are known to remove the spark arrestor the 1st thing with a new saw.

Replace the gas feed hose ,it's sucking air in and stopping the saw from running ,I'll bet it's an old saw that was laid up for years....

On second thought.... Trow it in the trash!!!! life is to short to [bleep] with a chainsaw that won't run.

I made money with people of your thinking ,finding a lawnmower ,snow blower ,chainsaw in a trash heap making it run ,then selling it.

No Harm Intended with this post..

In regards to ethanol blended gas ,I strongly recommend using marine grade stabil fuel stabilizer in all small engines it will save you money and lots of grief