# Homelite Trimmer Walbro Carb Adjustment



## OptsyEagle (Jul 17, 2007)

I have a Homelite Trimmer model UT20779. The last time I used it I found it started great and idled well but didn't like the high speed acceleration. I looked at the spark arrester and it was fine (black but the holes were quite clear). I decided to give it a seafoam treatment through the carb throat and in the spark plug holes, to blow out any carbon in the motor. After that it seemed to work OK so I am not planning on doing much about my top end problem until the problem returns (I doubt the seafoam would fix it).

I figured my next thing to do would be to adjust the high speed jet in the carb. My carb has two screws, side by side. The left one has a plastic piece on it with a slotted end that I suppose I could turn with a small standard screwdriver. The right screw only seems to have a metal rod on it. Nothing to put a screw driver in. I think this is my high speed jet and I am wondering how it can be adjusted. Does this metal rod come off or do I grab it with needle nose pliers and turn or something else? Anyone have one of these and can advise me on it. 

Also, if I am having a high speed bog and staul, do you think I should turn it clockwise to lean it out or the other way ... or just try both directions?


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## paulr44 (Oct 14, 2008)

First, as a factory-trained and certified technician, I cannot condone adjusting carburetors beyond the scope of the EPA caps that you describe covers the idle-mixture screw. The high speed is non-adjustable in your case. To adjust a carb. with limiter or tamper-resistant caps is a violation of EPA law and subject to heavy fines (beyond the limit of the cap).

That being said, I will tell you this: MANY of the low-end equipment (box-store) have carburetors that are so cheap, and given the corrosion issue related to alcohol bearing pump gas, that you're often better off replacing a carb. with GUARANTEED results (save for a vacuum leak or other problem co-existing), than to try and rebuild it.

We have many units we CAN adjust as prescribed by factory protocols that have been approved by the EPA to return units to proper operation and still maintain emissions limits. Technically, you as an individual are not PERMITTED to buy the tools to adjust said carburetors, however there are unscrupulous vendors out there selling said tools on the internet.

Bottom line is, if it's running lean and there's no vacuum leak or fuel filter/screen restriction there's GUM or CORROSION in the carb. Adjusting it may correct it temporarily, but the problem will surely return in time.

My OWN trimmer carb. from 2 winters in the shed without having been run dry was one of the worst corroded carbs. I've seen. NOW I run canned fuel, such as Stihl Moto-mix or Redmax. Canned fuel has NO alcohol and a long shelf life after opening so given my limited trimmer use it's a no-brainer.


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## OptsyEagle (Jul 17, 2007)

Thanks for that. I didn't know they were actually trying to prevent me from adjusting it. I thought that's what adjustments were for. I would also think that a new carb for a $99 Trimmer would be price preventative but I have not looked into it. Also, since I don't even know that the problem is my carb, I might be resistant in buying a new carb.

The fuel filter if I recall is in the gas tank itself. Is it easy to clean or is it also a replacement type part? Where would I look for a vacuum leak?


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## paulr44 (Oct 14, 2008)

The fuel filter on all trimmers is replace-able. I had one recently made by MTD for which they didn't list a filter, nor fuel lines, but the whole tank with lines and filter was like $5.00, which is about the cost of an over-the-counter filter.

The carburetor was like $23 for that same trimmer through MTD, and close to $40 through Walbro. There is no "average" or standard - you have to check each situation out for it's own merits.

Vacuum leaks can be tested for _to a degree_ without special equipment. A spray-can of carb. cleaner is needed. Remove the air filter cover, as often the air is drawn in from behind and that can affect the test. BEING MINDFUL THE SPRAY IS FLAMABLE and MUFFLERS GET HOT enough to ignite the spray, and DOING THIS OUTSIDE, run the unit and spray a bit at a time around the cylinder base and intake manifold. We usually spray around at least one crankshaft seal if accessible - some box-store units you can't get to either one with the unit fully assembled.


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## OptsyEagle (Jul 17, 2007)

Thanks Paul. Appreciate your help.


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## Jeremyf455 (Aug 14, 2020)

paulr44 said:


> First, as a factory-trained and certified technician, I cannot condone adjusting carburetors beyond the scope of the EPA caps that you describe covers the idle-mixture screw. The high speed is non-adjustable in your case. To adjust a carb. with limiter or tamper-resistant caps is a violation of EPA law and subject to heavy fines (beyond the limit of the cap).
> 
> That being said, I will tell you this: MANY of the low-end equipment (box-store) have carburetors that are so cheap, and given the corrosion issue related to alcohol bearing pump gas, that you're often better off replacing a carb. with GUARANTEED results (save for a vacuum leak or other problem co-existing), than to try and rebuild it.
> 
> ...


How do I know which carb I have? most of the numbers and such are long gone.


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## Milton Fox Racing (May 27, 2014)

Can you post a few picture from different sides and overhead of the carb in question....


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