walbro carb setup

Old 09-10-08, 03:01 PM
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walbro carb setup

I get a similar problem when I rebuild walbro carbs. I have a LOT of small engines, weedeaters, edgers, chainsaws. Most have Walbro carbs on them. I rebuild them, replacing the diaphram, and screen, but not usually the needle and spring. Blow the whole thing out with gumout and compressed air checking all the fuel passages for trash. Reassemble and usually the thing will run but not unless some choke is on, usually half choke. WHen I put it on no choke and give it gas it just falls on it's face and usually dies. restart it and it will idle just fine, give it gas and bogggg... The one I did today I did NOT change out the fuel tank filter which I will do, but regardless as to whether I do it or not doesn't seems to make a difference. I also usually replace all the fuel lines with new lines. I can't figure out what I am missing.
Old 09-10-08, 05:14 PM
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Are the carburetors your working on rotary valve carburetors??
Old 09-10-08, 05:15 PM
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Don’t feel like the lone ranger. Two-cycle engines have whipped more people than you and I know put together.

I like to think I am an accomplished mechanic, fact is occasionally one will beat me to death. Matter of fact I have one in my shop now. I have considered not working on 2-cycles many times but I still do. They are easy to lose money on especially the inexpensive ones. I think it is the challenge that sucks me in.

When troubleshooting 2-cycle engines, symptoms often make you think it is the carburetor when it is not. It is easy to go off on a tangent when troubleshooting 2-cycle engines and we think the carburetor is an easy target.

With 4-cycle engines, you need cylinder compression, fuel and ignition. Two-cycle engines cylinder compression, fuel and ignition and it is critical the crankcase on a 2-cycle must be able to hold pressure and vacuum. Crankcase oil seals and gaskets may leak either on the pressure side or vacuum side.

Two-cycle engines require special tools unique to 2-cycle engines, either purchased, improvised or homemade.

Most often, when I open a carburetor from a 2-cycle engine I fully test and rebuild it. That means pulling welch plugs and cleaning behind them. I do this because when I did not I often had to go back and do it anyway.

Only use spray carburetor cleaners, never dip a 2-cycle carburetor.

Service manuals are free to download at the Walbro website. Be sure to get the manual labeled “Diaphragm Carburetors”.


Good Luck
Old 09-10-08, 11:20 PM
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I've gotten to the point where I don't go to too much trouble on 2-stroke carbs. Labor is too valuable to spend on them, and I've had some that still wouldn't work right after 3 hours of cleaning, testing, adjusting it. Nowadays, I'll open one up and if it looks cleanable and buildable, I'll do it..but if it doesn't work, I quote another carb. On occasion, on higher quality items (high-end saw, etc..), I'll spend the time and effort to work with one and get it right. I also have considered not working on low-end 2-strokes because of the likelyhood of losing time and money on them.

Are you re-setting the H and L screws? Do these engines have sufficient compression? What kind of carb cleaner are you using?

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