Checking Compression On A Husqvarna Weedeater

Hi,

I have a weed eater , Husqvarna ,that will only start and run badly for a few minutes and then die . Cleaned and rebuilt carb ,new plug , new lines , new primer and cleaned fuel and air filter . Muffler clean too , at least screen is ! Zama carb on it .Primes up good . It has been adjusted by three different small engine mechanics , but to no good . One was a Husqvarna certified mechanic .He checked comp. on it and said that it was low at 70 pounds . I didn't see needle scale . Got home and used a comp. tester from Autozone that was designed for cars, but had an adapter that fit it . I was getting 90 pounds and up . I kept pulling rope and it topped out at about 130 lbs and wouldn't go no higher . Wasn't sure as to how to test a weed eater with it . Instructions said to let car motor turn over at least five times and then check comp so I pulled on rope 3 to 5 times like I was going to start it . Is this right ? How would you guys do it ? What is good comp on it ? What is needed enough to make it run at least ? Thanks for any and all help .

Whizkid
 

The weed eater engine is very small, so you need to pull it through several times to fill the hose volume etc. in the compression tester. Once the reading flats off (stops increasing) you can read the gage. Pulling it through addition times will not increase the reading. 130 PSI should be okay.

You might check the crankcase seals for leakage. If the engine uses reed valves (not piston port system) check the reed valves for sealing. I have seen a saw dust particle trapped under the reed valve on a chain saw - that chain saw stumped several mechanics.

Good luck - I have several Husky products and they have been good performers for me.
 
You honestly can not clean chainsaw/trimmer type carbs completely unless you remove the welch plugs to gain access to all of the small passages.

New Sthil products now calls for the carbs to be replaced every three years.

Just replace the carb with a new one and stop fighting the headaches trying to work with it. For once they go bad they will never be good again if a basic cleaning does not fix it.

Husqvarna products have really gone to the dogs in the past few years. You either get one that runs good or one that is not worth it's weight in scarp.

I have replaced nearly all of my equipment with Echo and will be hard presses to buy Huaqvarna or Stihl again.

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Have you removed the muffler and checked to make sure that the exhaust port is clear? If the exhaust port has a lot of carbon buildup. The engine will run rough and the warmer the engine gets the worse it will run and sometimes to the point that it will shut down.
 
I work as a small engine technician. 130 psi. is about minimum for that engine. That said,

In defence of the other tech., I test compression on almost every 2 cycle that crosses my bench. So far, I have gone through 5 compression gauges in the last 8 years. Usually they gradually start reading low and it takes a while to catch on.

Unless you have a crankcase leak, like a bad seal or something like that, your trimmer should run with 130 psi compression.

Most likely you do have carburetor problems.

You do really need to take the muffler off and make sure it and the exhaust port are clear of carbon. Also, a plugged exhaust can cause an abnormally high compression reading on 2 cycle engines.
 

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