Adjustment? Walbro WT 149A Carb.


Old 07-07-08, 08:47 AM
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Join Date: Jul 2008
Location: North Platte, NE
Posts: 1
Adjustment? Walbro WT 149A Carb.

Do you know the proper adjustment of the (L) & (H) Screws on a Walbro 149A carburetor? This carb. is on a Ryobi Model 410r engine and my owners manual only gives me the adjustment setting for the (L) screw ... 1-1/2 turns counterclockwise. I do not know what the setting for the (H) screw should be. The engine has good spark and sometimes will run briefly as I try different (H) screw settings.
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Old 07-07-08, 10:49 AM
Join Date: Jun 2008
Posts: 9
Initial settings for both the idle and high speed needles are 1.25 turns out.

If you are having problems getting it started, the LAST thing you should do is try and adjust the mixture screws. There is a 99% chance this is not the issue.

Check the fuel lines and inlet filter in the tank. They dry out and crack or break over time. If it's more than a couple years old or since the carb was serviced last, I'd replace the diaphragms/gaskets in the carb after disassembly and good cleaning. Kit is about $5 from your local repair shop. Pay attention to the order of gasket vs. diaphragm. They are different on the pump side vs the metering side of the carb. Clean the inlet screen under the pump diaphragm as these catch a bunch of crud. A can of carb and choke cleaner with the red straw on it to target the stream works great for this task. I'd put in a new plug for good measure.

BTW, if you go to the Walbro site, you can download a service manual for the WT series carb for more info(or any of their carbs for that matter!!!). You can also retrieve the part number of the gasket/diaphragm kit to take to your local dealer.

Beyond these items, you look at a plugged muffler(spark arrestor), loose cylinder or carb causing an air leak, and finally check the cylinder for scoring by removing the muffler and looking into the exhaust port. Obviously, the first two of these is easily repairable while the last is reason to junk the unit and start new!

Let us know how you make out!

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