Checking Compression On A 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
 

I had one that ran like that several years ago and it turned out the piston rings were seizing up and I fixed it by taking off the cylinder and freeing them up, WD-40 helps with that BUT if you're getting those kinds of readings on the gage I seriously doubt that that is your problem. I'd look at the fuel system first but those things can be a real PITA when they take a fit! Good luck to you! :)
 
Two cycle I assume? You say the exhaust screen is clean. Is the exhaust port clean?

I doubt compression is your problem, unless something really strange is happening with your piston/rings. I had one chainsaw fool me once. It pulled over like it had compression, but refused to run. I finally found where one of the rod bearing needles had escaped and grooved up the piston and cyl. where you couldn't see it from any port.

Is this engine piston ported, or does it have a reed?

If everything else really is OK, you may have a crankshaft seal leak, or some other odd crankcase leak. The little Homelites, when they first came out, would leak where the halves of the crankcase were "glued" together around the bearings. That was my introduction to RTV silicone. Homelite supplied it, black. I took many of those saws apart and resealed them.
 
I recently put rings in an original Weed Eater and a Poulan 35. I ordered rings online. Upon receiving the new rings and comparing them to mine, I did in fact have worn rings on both machines. I didn't have all that many hours I thought. I was using Stihl Premium gray bottle 100% Syn at their recommended rate of 50:1. Got to looking at the manual for one of them, forget which, and it said 40:1 was the required mix. So I upped the mix after the rebuild.

So, after all that work and all I put them to work and the 35 ripped out the woodruff key slot on the flywheel after about a spool of string and the WE ran for a couple of hours and just quit, wouldn't restart.

I threw both in the trash and went to Attwoods farm store and bought a Stihl FS-50 C-E. It weighs 11# instead of the 17 (I measured) on the 35, has a curved shaft (my choice over the FS-56 with gearbox) rather than the straight pipe and gearbox the 35 has, has the Stihl easy start neither has (getting too old to have to pump and pump an outdated designed manual starter) and has a 7" longer shaft length for my 6'5" frame the WE doesn't have which is sweeeeeeet. So much for that.....life is good.
 
If it starts and runs badly as you described, I would say the problem is not compression or it would not start. My guess is the problem is in the carb. There is a strainer in that carb (I think). It may be difficult to find because it is under the housing where the fuel comes into the carb and the strainer is small. Go to zamacarb.com and look at the trouble shooting guide. I would put in a new diaphragm while I had it apart just for good measure. Again, follow the trouble shooting guide and you can fix this yourself without help of the EXPERTS. Good luck.
 
Is your husky a 2 or 4 stroke? I have a husky 4 stroke and bought a new carb on line for under $40.

My 4 stroke starts on first or second pull, which is a very easy pull.
 

1) with carb removed to can inspect the cylinder and rings.
2) confirm fuel lines are connected to the primer blub in the right direction. It has a check valve and directional google it.
3) Don't condemn the carb till you are positive fuel supply and lines are good. They are clear enoufh you can tell if fuel flow is good and not getting air in them.

I replaced the fuel lines on a saw a few weeks ago I went to the small engine shop and got 3ft of line that matched my sample. It sounded like your issue and I made every mistake you could make.

Hooked to primer wrong fixed that a no go, in the end I googled it and found the supply line was smaller than the rest, what was happening was the line supply line going into the tank was to big it was pinching it and starving for fuel. I got a smaller line for the supply and its a fix.

In all fuel supply issues I have ran into you could tell fuel supply was a issue from the way the primer felt when you pumped it.
 
Check the muffler exhaust screen and clean it. If it is partially clogged it won't run right. Just repaired my Echo back pack blower with a new carb. This was after what I thought was two thorough carb cleanings and rebuild and it still wouldn't run right. New carb fixed it.
 
Quick way to check compression. Grab pull handle , lift unit up by it. If unit drops or rope pulls out without lifting unit , low compression . You can remove muffler and plug, inspect cylinder and piston for any scoring. Make sure fuel lines are hooked up the correct way . Some of those carbs cant be rebuilt . New carbs are pretty cheap these days . I have an ultrasonic cleaner and even that wont get some check valves and passages clean .
 
(quoted from post at 08:21:27 04/18/17) 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

Pull the muffler and look at condition of piston and exhaust carbon buildup..
The proper way to check compression is to turn over several times while holding throttle wide open. Compression will build to max and no higher.
These Chinese carburetors are notorious for giving problems.
In most cases, a new carburetor is only slightly higher then a repair kit--- !?
Two strike engines need at least 110--120 psi compression to run properly and new have approximately 140---150 psi.
Air leaks give more of a problem at low rpm and idle, but can cause bug problems if not corrected.
 
Sounds like enough compression.

Price a new carb, most are unbelievably cheap, try Ebay.

Replace the carb, fuel lines, be sure the fuel lines are connected right, Google it.

Most likely that will fix it.
 

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