# Troy-Bilt TB22 EC Compression?



## TerryinFL

Above mentioned weedeater stopped idling and would only run full throttle at half choke. Dismantled most of Walbro WT973 carb, sprayed w/carb cleaner and blew dry, replace most everything readily accessible and reset the metering lever w/appropriate tool. 

Reassembled, primed, set choke to full and pulled the rope a few times until engine fired. Moved choke to 1/2 setting, squeezed throttle to full and pulled rope a couple time until the engine started and it ran well at half choke then it stalled when the choke was opened. Tried again, started engine, left choke at 1/2 closed and released throttle and engine stalled. Gas is reasonably fresh and gas lines appear to be in good order. To eliminate possibilities I'm wondering if the compression, which tested at 90 lbs, at best. is the issue. Don't have tool to adjust L or H settings - yet, so I can't address those settings.


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## Rentahusband

90 is on the low end for compression. Did you replace the filter screen in the carb? There could still be an obstruction in the carb. Make sure the carb it tight and there are no air leaks between the carb/engine. It could be the L speed adj. Those adj screws are a pita without the proper tool.


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## TerryinFL

@Rentahusband
Thanks for the info and suggestions and yes I did change the filter screen. Also removed the muffler this A.M. only to find that the spark screen was inaccessible but looked relatively clear and there was minimal oil around opening. Hate to spend the bucks for the tools for adj screws but may be necessary since I'll have 2 cycle operated equip on into the future. My main concern with the unit we are discussing is that the low compression may be the primary cause run issues.


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## TerryinFL

Just happened to think of something else. What is an acceptable compression psi range for 25cc engine?


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## Rentahusband

I believe an acceptable compression range is generally 110-125. I would try and find some way to adjust the mixture screws. Initial setting for both H/L is 1 1/4 turns from seated posisition. Your L speed screw may need to be turned out a little more that it's current setting. If the L speed screw is turned in to far, it will not allow enough fuel to idle properly. Some have used a dremel tool to cut a slot in the screw and adjust with a flat screwdriver. You may have to cut into part of the casting of the carb if the screws are surrounded by this. Try loosening the gas cap and see if that helps. If the cap is not venting properly, the engine will not get the peoper fuel to run. There may still be some restriction within the carb.


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## paulr44

MTD service manuals are free:
http://support.mtdproducts.com/app/answers/detail/a_id/10584

Your manual is here:
http://service.mtdproducts.com/Training_Education/769-02765-PSM-TB25BP.pdf

MTD parts look-up is free:
http://mtdparts.arinet.com/scripts/...=Empartweb&loginID=mtddealer&Loginpwd=6922941

See page 12 and 13 of the 25cc of the 2-stroke manual (769-02765), which states
that compression must be at least 110 PSI, which RENTAHUBBY points out accurately.

HOWEVER, I'd like to point out that if you use a compression gauge with an extension hose, that HOSE must have a SCHRADER valve in the tip else the hose becomes an extension of the combustion chamber volume, giving you a false LOW reading.

If you feel the compression is sufficient, spend LESS than $25 on a new carburetor. All 3 versions of the TC22EC use the same carburetor, P/N 753-06190.


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## OptsyEagle

From the service manual above, page 9:

Note: If the engine has less then 110 psi compression, the carburetor will not have enough vacuum to draw fuel into the engine.


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## TerryinFL

*Resolved - nothing to do w/compression*

Sorry for taking so long to respond to all the helpful input. Since my last post I ordered both a mixture adjusting tool and a metering lever gauge then waited for my wife to clear her garage sale stuff off my work table in the garage. Now then, with tools in hand and garage sale is over time to get at it. So today I reset the metering lever which was at least 1/32" low, seated the adjusting screws then turned them both out 1 1/2 turns per your suggestion RentAHusband. Closed the choke, primed the engine and pulled the cord a couple times 'til it fired. Set choke to 1/2 and pulled a couple more times to start engine. Let it run a min. or 2 then opened the choke and it ran like a new one! Adjusted the both screws, according to the manual, and the idle speed screw then put it to work without a hitch. Great point Paul, the gauge I used is for a car engine and has a rubber hose so I probably did get a false reading. Thanks to all for your much appreciated help!


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