Small Engines (Lawn Mowers, etc.): Carb Adjustments, poulans, adjustment screws

Question
I had to copy/paste this, as Allexperts seems to only let you reply so many times. The link for the service manual you pasted didn't work; it was actually a copy of the link pasted above it. Here is what the carb adjustment screws look like: http://i.minus.com/ivTSFMtYz6uTp.JPG



QUESTION: Hi. I bought a carburetor (Walbro WT-628) for my trimmer, but can you tell me if they are difficult to adjust? I adjusted the idle screw to where the trimmer head isn't spinning, but the engine dies after a few seconds of throttling. It seems to idle fine for some time, but eventually dies.

Here is what it sounds like: http://soundcloud.com/jarbs2154/trimmer-3/s-7V6Up

Thanks

ANSWER: What trimmer do you have?  Has the carb been rebuilt?  

If you have an air/crankcase leak or low engine compression the carb can be very difficult to adjust.

Let me know the brand and model of trimmer you have.

Eric

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QUESTION: Poulan Pro PPB200. The carb is new, and the compression was checked out as being good.

ANSWER: What was the compression reading?  How many PSI?  Had low compression on 2 Poulans.  If it is less than 100 PSI it will not run right.

What about an air leak?  I've lots of Poulans with a leaky crankcase o-ring.  Will not ever adjust or run right with an air leak.

These are the two most common problems I find with Poulans where the carb will not adjust.

Eric

---------- FOLLOW-UP ----------

QUESTION: It wasn't that the carb wouldn't adjust, it was that I was wondering if it is difficult to adjust. I have never done it before. Following the manual, I adjusted the idle screw, and had planned on getting the tool to adjust the high/low screws. A shop had told me previously that the compression was good, although I'm not sure if they checked for leaks.
Answer:  Most manuals state to set the initial setting at 1 and 1/4 turns.  However, based on the link below, this is changing.

http://www.walbro.com/techtips.aspx

The service manual link below is very helpful as well.

http://www.walbro.com/techtips.aspx

Can you send a close of picture of the needle adjustments?  Sometimes you can use other or modified tools and not have to buy the "special" tools.

Eric

Answer
Those needles can be challenging to make tools for.

One option you have is to use a dremel tool with a thin metal cut wheel on it and cut slots in the adjuster screws so you can adjust with a small flat blade screwdriver.  Of course you will have to cut through the carb housing as well.

You could also use a hacksaw but it will take forever.  A dremel will get the job done in about 5 minutes.

Eric