I have a redmax blower that uses that carb. The problem is that the EPA has the thing running almost too lean. Inside the cylinder that rotates is a metering rod. If you look closely, as that cylinder rotates, it moves slightly up and down. That pulls the metering rod in and out of the pickup tube. The tube has a slot in it, and the position of the rod determines the amount of fuel that gets drawn through. If you take the carb apart, you will find a tiny brass jet. I had the same problem as you, and I solved it by drilling the jet two sizes bigger. Don't remember the size, but it was almost the smallest drill in a set of orifice drills. I would recommend that you go only one size at a time, as with a hole this small, it won't take much to go too rich.

Bingo! You were dead on. I did go up one size and what a difference it makes! It started on the third pull and seems to be doing fine now. One thing I noticed with the larger jet size is that the idle rpm seems to have gone up, I guess this is due to a more richer mix. I can live with that.

Thanks fix_it for your advice.

There should be a set screw for the idle speed on top of the carb, where the trottle cable attatches. Your results are the same as mine. I would have to pull it 40 to 50 times. Now it starts on the 3rd or 4th pull.

Thanks, I did lower it a bit. Did get some good work out of it today.

Hello all.

Is this Walbro design rotary carburetor the same as the "rotary valve" technology used in Kawasaki 90cc 2-cycle motorcycle engines in the 1970's ?

Good day.

I don't know anything about motorcycle carbs, but this is like a ball valve. There is a cylinder that has a hole in it. This sits in the carb and as the hole is aligned with the throttle bore, more air is allowed in. Also, as the throttle bore is opened, a metering rod is lifted allowing more fuel to flow from the jet.

Hello all.

Thanks fix it. I understand now about the Walbro Rotary Carburetor.

I removed the air filter cover on my string trimmer and looked inside the air intake as I worked the throttle.

And inside there is a cylinder that has a hole in it.
I think old Kawasaki 2-cycle motorcycle design used a rotating disc.

Good day.

Aha... Now you talk about the disc, I remember those carbs. I had seen those even on the 2 stroke yamaha 100cc bikes back in the 80's. No, as you have found out, these are little different and maybe not as sturdily built as those bike ones. These have more plastic and flimsy floats and diaphrams when compared to those old carbs.

They have even taken out the one puny screw that used to hold the fuel metering lever. Now it just snaps in!

As fix_it has said before, the only way to get these to start is to go up one or two sizes, otherwise, you will get a nice workout everytime you try to start.

Good Luck.

I have a brand new Husqvarna 130BT blower with a WYA-73 Walbro rotary carburetor. I cranks easily and has reasonable air fclow but my Husqvarna 125B blower will blow it into the weeds. I checked the RPM on both and the 125 develops 8,900 and the 130 only 6500. I disassembled the carb on the 130, cleaned it and put a new kit in it but the rpm stayed the same. The carb had some ethanol residue from the factory but I cleaned this out.

I think the rotary valve is not moving upward at WFO, which is why the rpm is limited to about 6,500. Any thought are appreciated.

BTW, the spark plug looks normal - a slight brown residue on the center electrode.