[kilr318]

I have a cheap older Poulan 2300 that revs at about 3/4 throttle when it starts. It does not 'kick down' as it warms up, and the throttle trigger actually causes the high-revving engine to bog a bit. Does this saw need a new carb, or is it time to junk it?

 

[K-B]

It's probably an air leak (lean running). On that saw, there's several possibilities. No. 1 is a cracked fuel line, which is relatively easy to diagnose. Just inspect the line for any cracks and leaks.

I've seen a lot of those saws with loose or broken carburetor mounting manifolds. (The plastic block between the engine & carb) Grab the carb and wiggle it to check for any movement (there should be none).

Other possibilities are a blown cylinder gasket, leaking crankshaft seals, a internal carburetor leak, etc. These can be difficult to diagnose without doing a pressure test of the crankcase, which requires some special tools.

Before you do anything to it, I'd remove the muffler and inspect the condition of the piston and the cylinder wall for any damage. Most of the saws have unlined aluminum cylinders, and will score very easily. Depending on how long it's had a lean running condition, the engine could already be trashed.

 

[bozodog]

Has this saw been sitting for a season? If so, it's likely bad gas.. Drain and refill with fresh mix. Adding a stabilizer, like SeaFoam or Sta-bil.

There are tiny passages within the carb that get clogged up. Sometimes just running with new mix and the additive will clear things up.

Try tuning the carb...

A typical starting place for most carbs is about 1.25-1.5 turns out from gently seated on both needles. Typically this will be quite rich, but it will start. Tune in from there.

Once running, Start by holding the throttle wide open. Slowly turn the Hi needle in. Engine should smooth up, speed up. At some point, it will begin to stumble a bit. Back off until it's going as fast and smooth as possible, and then back off another little tiny bit, so the engine slows slightly.

Now go to idle. Screw Lo needle in until highest idle is obtained. After idling a few seconds, goose the throttle. If the engine stumbles or quits, open the Lo needle a 1/16th turn at a time until the engine accelerates properly.

Go cut! If the engine boggs under full load, oopen the Hi needle slightly more.

If it's still misbehaving, pull the needles (count turns!!) and spray carb cleaner into the jets liberally. Remove the air filter and spray well, inside and out.

If none of the above works, it's time to pull the carb apart for a good cleaning and a rebuild kit.

You can check for intake leaks by spraying around the carb base with the cleaner. (I doubt that's your problem)

 

[kilr318]

Great suggestions guys, thanks! The trigger is free, so I know it's not sticking causing the revving. I just replaced the fuel line a few months ago, so that's new. I use the saw frequently, and Sta-bil goes in every can I mix with the oil, so I don't think it's the fuel itself. I will look at the carb manifold as a potential source of my grief, as well as the muffler removal to check cylinder condition. It might be worth getting a new carb for $20 and try replacing that too.

 

[bozodog]

I doubt you'll find a carb for $20, a rebuild kit would cost about that.

 

[K-B]

That model has the fuel line in 2 sections, one section running from the carb to the handle base, from the handle base to inside the tank. Were both sections replaced? Was the in-tank fuel filter replaced also? The 2300 doesn't have the carb mounting manifold style that I was imagining (saw it after I looked up that model). But still check to make sure that the carburetor is not loose.

I'm still nearly sure that it's an air leak somewhere - the symptoms match perfectly.

A new carburetor is no longer available from the OEM.