Sounds like you have the carb real clean. Would look for a air leak somewhere, seals, gaskets, boot if it has one. Even if it's not adjustable it used to run ok the way it was so it would be a air leak or dirt, something like that . Steve

I'm not familiar with the engine or carb, but I have pulled my hair out on other 2 stroke engines with similar symptoms. After cleaning or rebuilding carbs and still having issues, it turned out to be the cylinder to crankcase bolts that had backed out a little, causing an air leak and the lean mixture. It's a long shot, but check the cylinder mounting bolts and backplate screws if applicable.

Good Luck!

I've had the intake manifold bolts vibrate loose from the engine & cause an air leak.

The diaphragm that drives the needle valve mechanism can look perfect but be stiff and cause the problem.

It sounds like it is a rotory valve type carb. It is not uncommon for the little wheel -- that lifts the valve as you open the throttle -- to wear out and cause your mixture to be lean. That "adjustment" on top of the throttle is just a bolt that removes the throttle plate. You will have to go to a distributor and have them look up the parts and explain them to you. Usually the wheel that lifts the valve is plastic and the valve is plastic. If your fuel intlet needle height is right and everything else is clean, you'll likely have to replace the rotory assembly.

A test: while weedeater is running, pull throttle plate outwards (it's on a spring holding it in). As you pull it out, you are enriching the mixture. This should cause the engine to suddenly run fine.

What is the completer model no. of the carb? So we can look it up and know more about of the carb. Later Butch

No response....

No really, I worked at a golf course at my last job. We had about a dozen trimmers with this style of rotary/slide valve carb. If you have checked everything else, I am almost positive this is your issue.

The original carbs had a plastic wheel that ramped the rotary valve outwards, which increased the area available in the main nozzle, as you opened the throttle. The new rotary assembly should come with a metal wheel.

I tried to find a place where you can order the rotary assembly online, but came up empty handed.

Part # is 34-530 and list for $11.09 if you can find it. None of the people we deal with have it either. Later Butch

ggoy--
I am having a similar problem with a Walbro on a 12.5 Kohler. I realize that the engines and carbs are completely different but if you find someone knowledgeable I would love to talk with him or her. Thanx.
tommyt

I found a PDF file ebook manual for the Walbro WY carburetor online that will help you, they also have a lot of other small engine carburetor manuals

http://carburetor-manual.com/walbro-series-carburetor-shop-service-manual-ebook-p-890.html

Here is a link that might be useful: Walbro WY Carburetor

HI i have been reading the forums above the problem i have is i can't get the plastic top part of the carb of it's a walbro wya carb there seems to be a brass cup in the centre anyone know how they come apart i'm afraid i might break it

I have a Walbro WY on a Husqvarna 22R trimmer. During use it flooded out and quit. A new kit (K-10-WY) did not help....nor taking it apart several times being sure all parts were in proper order. Also, pulling the starter rope pushes even more gas into the piston chamber. When everthing is dried out it starts right away but almost instantly floods out. Help!

Wayne, For the sake of learning and informing others, were you able to cure your Walbro WY flooding woes? If you did, do you remember what the culprit was?

In hopes of helping someone with this same problem, I thought I would share my solution. Those rotary valves wear out and can be difficult to find. Here's the solution: cut a couple of 2-3mm lengths of 1/4" fuel line. Put the throttle cable plate on the plastic rotary valve and insert he screws. Slide those pieces of fuel line onto the screws so they will be between the rotary valve and carburetor. This should give you just enough elevation to get the appropriate clearance allowing for proper fuel flow. Tighten as needed. Blue loctite wouldn't hurt. I assume washers would work as well but I just used what I had on hand. My backpack blower fired right up and runs great. Hope this helps!