Impulse lines?

[Byrdmando]

Do ALL saws have them? I have been given an old Poulan 2300 that hasnt run in years. I want to see if I can get it to run again and maybe give it to a neighbor that could use a kind gesture.

I have replaced the fuel line and fuel filter and put a bit of mix down the throat and got it to fire (that is pretty encouraging to me) but I do not see an impulse line anywhere.

Obviously I am fairly new to the internal workings of a chainsaw but am in the process of trying to learn all I can.

Thanks for any help.

 

[Andyshine77]

Some saws have an impulse passage in the intake block.

 

[zogger]

Do ALL saws have them? I have been given an old Poulan 2300 that hasnt run in years. I want to see if I can get it to run again and maybe give it to a neighbor that could use a kind gesture.

I have replaced the fuel line and fuel filter and put a bit of mix down the throat and got it to fire (that is pretty encouraging to me) but I do not see an impulse line anywhere.

Obviously I am fairly new to the internal workings of a chainsaw but am in the process of trying to learn all I can.

Thanks for any help.

Most likely the carb is gunked up and/or it needs new diaphragm and gaskets, etc what is called a kit.

You might get by with cleaning it. Carb comes off. pay attention to how the pieces come off, it isn't complicated but it is exact. Use a can of carb spray and clean everything, watch the teeny screen in there, don't lose it, clean it. if you order a kit (based on carb make/model) you get all new stuff. Spray through all the passgeways you find carefully as it can spit back at you, but this isn't hard to do either. Start with just little spritzes. Clean the outside off first before taking it apart.

 

[a. palmer jr.]

Your saw has an impulse hole in the base of the carburetor and a corresponding one in the intake. Make sure the holes aren't blocked off when you take carb off for cleaning.

 

[redunshee]

Your saw has an impulse hole in the base of the carburetor and a corresponding one in the intake. Make sure the holes aren't blocked off when you take carb off for cleaning.

Great advice. Your 2300 is an update to the venerable Poulan S25DA/CVA. Very strong saws for 38cc's. It is a reed valve saw and won't have an impulse hose like you may have seen on newer saws.

 

[a. palmer jr.]

Great advice. Your 2300 is an update to the venerable Poulan S25DA/CVA. Very strong saws for 38cc's. It is a reed valve saw and won't have an impulse hose like you may have seen on newer saws.

The pulse hose is mostly used on saws with the anti-vibe, it allows the engine to move and not be solidly mounted to the carb, tank, and rear handle on the newer designs. On the old ones, where everything is solid (my favorites) it is not needed, neither is the rubber manifold which occasionally splits and tears.

 

[heimannm]

Just to be clear about it, reed valves and impulse lines are not mutually exclusive.

Almost all modern two stroke engines use pressure pulses from the crankcase to operate a fuel pump diaphragm in the carburetor to pump the fuel. The impulse or signal can come from a separate line, normally a barb fitting on the crankcase or base of the cylinder to a fitting on the carburetor, or via a passage from the crankcase to the mounting flange for the carburetor.

SP125, reed valve intake, impulse line attached to the top of the carburetor

Nor are all piston ported saws equipped with an "external" impulse line.

Mac 6-10, piston ported, impulse delivered through the carburetor flange

CP70 Note the barb fitting just above the crank shaft - fitting comes from the crankcase

Titan 57, the impulse fitting at the base of the cylinder - circled in red

SP80 cylinder on the left, impulse barb is obvious below/left of the intake, PM700 cylinder on the right, impulse is delivered through the intake flange, note the third small hole in the bottom, center of the intake flange

As noted above, most modern saws with anti-vibration mounts will feature separate impulse lines since the carburetor is separated from the saw by a flexible boot. When the carburetor is hard mounted to the cylinder or crankcase, the impulse normally comes via a channel or port in the block and not by way of a separate line or hose.

Mark

 

[Byrdmando]

Thanks to all. That helps alot. Thanks for putting up with a newb.

Byrdmando
Bedford County, VA.