Chainsaw Carburetor Question

[mccutter]

Hurricane Ian is on the way so thought I would try to fix a non-running Craftsman (Poulan) 20" saw I picked up recently for $20. I figured the chain and bar were worth the price and it looked to be in good shape. That is the black saw in the pics.

I DO have an identical pair of different model Cman 20"-ers, the first of which is pictured below--the red saw. The second I also picked up for $20 a few years ago, replaced a gas line and it ran. Both have been checked for function the other day and start and run no problem. That first saw pictured cut 1000s of feet of downed trees into smaller sections to be brought to the curb in the aftermath of Hurricane Charley (2004). It owes me nothing and still runs great... The second saw could use a little tuning but runs and revs OK.

The black saw I'd like to get running as it is a little nicer than the red saws with alum. chassis (reds are plastic) and is 54cc vs 48cc. Looking at the crankcase, it appears there is what I think is a pulsing port nipple and I found a pic or two of a Poulan saw mentioning this but nothing definitive nor anything explaining/illustrating gas hose routing. The nipple DID have a little clamp on it with remnants of a hose. That hose is apparently a heat-resistant type vs the plastic style... I didn't see any kind of dedicated "hole" for a gas line in the chassis so it probably runs next to the on-off switch wiring. The top port of the carb (shown removed) was not connected to anything. There is no primer bulb nor place to put one. There IS a screw in the top of the fuel tank next to the fuel line to the filter. So where does the top port go to?

PS: the green arrow is pointing to an engine vibration damper stud that is seized in the chassis that I will have to make a puller for. I tried juicing it and tapping it but I don't want to break the ear off the chassis. I decided I didn't need to pull the engine out of the chassis that badly...

[Samcord]

I don’t know but this may be helpful, or at least entertaining. https://youtu.be/PKMzBNMgM-4

[Ironman]

Originally Posted by mccutter

The top port of the carb (shown removed) was not connected to anything. There is no primer bulb nor place to put one. There IS a screw in the top of the fuel tank next to the fuel line to the filter. So where does the top port go to?

I would look at all the other Poulans you have and copy the hosing and routing. They most likey use the same carburetors.
I believe to top carb port is the pulse line. It goes in by the diaphragm in the carb

[mccutter]

Originally Posted by Samcord

I don’t know but this may be helpful, or at least entertaining. https://youtu.be/PKMzBNMgM-4

It was enlightening, (fucking EPA! ) but I think my gas cap might be inward vented to relieve suction. I'll look at it next time I work on the saw. One of the Stihls she shows I came across the hoses, carb and kit with filter on debay for "cheap". LINK and pic below. No such kits were found for the black saw... I DID find a pic of a crankcase with port shown.

Originally Posted by Ironman

I would look at all the other Poulans you have and copy the hosing and routing. They most likely use the same carburetors.
I believe to top carb port is the pulse line. It goes in by the diaphragm in the carb

I can verify that the pulse hole is in the intake port and carb of the red saw. I know this because when I first got it back in 2003, it was 1/2 price open box, but ran like shit. I took it apart and noted the intake "manifold" and gasket were deformed and leaking. This is how I know it had the pulse port built in. I put it back together and took it to a nearby repair center (when Sears used to have them...). Even with telling them what was wrong with it, it still ran like shit a couple weeks later when it was ready (no charge). I brought it back to Sears with the intent on getting my money back. The salesman walked to the shelf, grabbed a brand new saw and handed it to me. THAT saw has run great just about its entire life so far...

[mccutter]

With NO sample in hand, I went to ACE Hardware and picked up a couple feet of gas line that "looked" to be the right size. And it was--damn, I'm good! Had previously downloaded the owner's manual from www.manualslib.com which barely provided any relevant info.

The gas cap has a small rubber "oval" in the center hole I believe is a vacuum vent. The engine side of the carb has no pulse hole (that is a blind dimple in the pic).

Re-used the old filter but ran new gas line. A "trick" to feed the line into the tank is to cut it on an angle which helps to start it through the hole. Having the perfect size helps a lot, too--it should be quite snug with a little "give". Too loose and you'll get fuel leaks. The carb nipple tubes were cleaned with scotchbrite as was the crank nipple using the strip cut from it and pulled back and forth. I keep a "scrap" piece on the bench for such purposes.

I happened to have the PERFECT duckbill pliers to put the crank nipple clamp on. I also used channel locks to push the semi-seized cushion stud through then re-tightened as I have no need to remove the engine anymore.

Going back together, I put shrink-tube over the bare connections to the on-off switch apparently replaced at one time by the PO. And of course, one connection promptly broke the three remaining strands of wire holding it together... So I had to cut the shrink-tube off and put another connector on and re-apply the shrink-tube (not shown).

Put the handle/trigger back on (no bar or covers yet), put some fuel in it and pulled over a dozen times and nothing. OK, I can smell fuel, let's check the spark. Pulled the spark plug, put it back in the cap, laid it on the cylinder head next to the plug hole and pulled. Nothing. HMMM, switch says "ON", lets try the "OFF" position. Pulled again and immediately saw a spark followed by a WOOSH of a little finger flame out the hole. Yup, got spark now... Put the plug back in and it started in two pulls!

At this point I cleaned the air filter, put the covers back on, put bar oil in the tank, installed the bar and chain, greased the bar end, put a little more fuel in the tank then started it again. After a burp on full choke, started first pull on 1/2 choke, then 10sec to no choke. Revs up quickly and smoked a little at first but isn't too bad now. A little smoke is good as it keeps away the skeeters! The chain oiler is a little too juicy for me but it is adjustable which is nice. The chain itself needs sharpening as it wouldn't even cut into cardboard on the ground and just skated across...

[milomilo]

Gotta love it when a plan comes together.