Chainsaw Won't Accelerate (Zama Carb)

[Rocky_LC]

I have a Poulan Pro 220LE (I know - get a Stihl*) that doesn't accelerate. When I hit the gas it will initially start to spin up, then immediately bog down. It seems to me that it is not getting enough fuel to run at high speed.

It has a Zama W020 carb, and I've got a carb rebuild kit, but I had taken it apart once before, and I didn't see anything that looked bad, so I am wondering if this sounds like clogged jets, fuel lines, etc.

Here's a link to (what looks to me) to be a reasonably explanitory manual on 2 stroke carbs.

USA Zama : Tech Guide​

Any suggestions, in case I rebuild the carb and end up with the same problem?

Reading the other post - I am going out now to check the muffler / spark arrestor, but it sounds normal. I'll report back.

Thanks

Chuck

* PS - I just bought one, this saw is the back-up.

 

[fj40charles]

How old is the fuel? Clean air filter?

 

[Rocky_LC]

I changed the fuel and filter first time around....

 

[splitshot]

If it's not the arrester..
Could be sucking air from fuel lines, priming bubble, or the welch plugs inside the carb. Had the same issues on a couple of weedwackers. If you don't want to mess with it, and not in a huge hurry, bring it on by.

 

[D'Animal]

This is good information

It sounds like you are getting too much air.

If it's not the arrester..
Could be sucking air from fuel lines, priming bubble, or the welch plugs inside the carb. Had the same issues on a couple of weedwackers. If you don't want to mess with it, and not in a huge hurry, bring it on by.

A leaking welch plug in the carburetor can cause two problems. 1st one is it will allow air into the circuit and you will have the symptoms you described. The other is it will run rich. The fuel will flow into the carburetor and will seep past the welch plug and can cause it to flood.

 

[Rocky_LC]

Thanks for the advice. I will see what I can do to check this theory out.

Regards -

Chuck

 

[dohcdelsol93]

on many engines with this same probem you can simply just open the the high speed jet 1/2 a turn to get it to rev properly again assuming your fuel lines and everything else is in working order along with clean exhaust port/spark arrestor screen.

You will probably need a special tool to adjust the carbs on this saw unless it's got a few years on it (thank you EPA). Otherwise you'll have two plastic limiter caps on the carb that must be removed before adjusting.

when adjusting 2cycle carbs be careful, if you set the adjustment too lean you can burn up your saw.

 

[Rocky_LC]

Thanks for all the good advice, dohcdelsol93 & splitshott.

Actually I have 2 nearly identical saws, one a Poulan, one a Craftsman.

My 1st plan is to swap carbs. If the craftsman runs with the carb from the problem saw (Poulan), that will tell me that the issue is in the tubing or the primer bulb. This is number 1 as I already have the carb removed.

If the saw doesn't run right, then it's back to dohc's advice.

Thanks for the advice. Good to know about the service from AOP.

Splitshott said:

After checking the arrestor..

First thing I would do is replace all the fuel line, priming bubble, and rebuild the carb. If your zama has those oblong welch plugs, you will need a special tool to install the new ones (I don't mess with them, prefere Walbro's because they are round, don't require a sealant and I have a tool fabbed up to install new ones). Pay extra attention to the end of the metering lever and make sure it is flush with either the bottom or the top of the housing (carbs will vary, look at the old one before removing the needle).

Two of the units I recently worked on, above didn't cure the problem, so I gave Dan a call. He said the early Zamas had a high sealant fail rate. Stihl got sick of dealing with it, so they bought out Zama, newer models don't have a problem.

Anyrate, if you need a new carb, it'll run about 85 bucks, I would sugest going to Marie @ American Outdoor Power on Stone ave. Best Dealer in So. Az. IMO. Service is excellent also.​

 

[D'Animal]

The Walbro carbs use real welch plugs that are dome shaped and you tap them adn they swell to seal the port.

Zama carbs use covers that are glued into place. You tap on them, you destroy them. Seal All is the best thing to use to seal them. It comes in a yellow tube and is sold at most ACE/Do It/True Value Hardware stores.

 

[dohcdelsol93]

unless your going to rebuild carbs for a living don't worry about going to the store to buy special sealer to seal your welch plugs.

Just steal a bottle of your old ladys finger nail polish (not her favorite color). After you re-seat them put a thin layer over the welch plug where it meets the carb. Let it dry about a min. then go with it.

I've never had an issue with welch plugs coming loose on poulans. I had a rash of FS 80's, FS 85's, and IIRC FS 90's that all had issues with welch plugs coming loose (flooding engines with gas) These were all Zama Carbs but Zama carbs made specificly for Stihl.

 

[D'Animal]

In certain states the fuel or more correctly the additives in the fuel will remove the finger nail polish better and faster than finger nail polish remover.

Just steal a bottle of your old ladys finger nail polish (not her favorite color). After you re-seat them put a thin layer over the welch plug where it meets the carb. Let it dry about a min. then go with it.

 

[dohcdelsol93]

it's not uncommon to find the factory sealant on zama/walbro welch plugs eaten of. If it wasn't for todays fuels...id be broke.

 

[splitshot]

Correct me if I'm wrong, but what Walbro's require sealant on their welch plugs?

it's not uncommon to find the factory sealant on zama/walbro welch plugs eaten of. If it wasn't for todays fuels...id be broke.

 

[dohcdelsol93]

any zama, walbro, tillitson, TK, Nikki carb that has internal welch plugs that seal highspeed jets or low speed jets have to be "punched" or "pressed" in place then sealed.


Even on alot of 4 cycle carbs you have welch plugs on the outside of the carb (briggs, kohler, honda, Kawasaki, tejunksee) that much be pressed or punched into place then sealed.

You just need a thin layer of coating (i prefer fingernail polish but to each his own) to make sure the plug has a tight seal.