Weed eater compression

[doc623]

Took Homelite weed eater to the repair shop.
It was running a couple weeks earlier and when tried to start a coulple days later it would not start.
Installed a new spark plug to the mfg gap specks. Would not start.
Fuel line is getting new fuel to the engine.
Took it to the repair shop. Called this AM and the shop said that it did not have enough compression to start.
I quess the compression is checked by a guage?
The unit is older but has not had hard use over the last 3-5 years.
As a note also took a Lawnboy walk behind mower to the same shop a couple of weeks ago and quess what. The engine was shot as it did not have enough compression to run and would be to expensive to repair.
I scrapped the mower, however, I am now woundering about the week eater with similar problems.
Too similar?
What are some of yall's thoughts.

[moopups]

Yes, compression is checked by inserting a rubber tipped gauge into the spark plug hole, and then the pull starter is activated a couple of times. The gauge registers the poundage that is present. Any engine with at least 60 pounds should at least start.

I am suspect that both engines are two stroke? Older two stroke engines often have a hard to diagnose problem. In that a two stroke's fuel is delivered via a scavenger port that is located in the cylinder wall from a pressurized crankcase, the crank seals at the outer ends often deteriorate over a period of years. The only way to correct the problem is to separate the two engine halves and replace the seals.

If the weed eater tries to start, maybe hits 4 or 5 times before quiting that is an indicator of failed seals. This applies only to two stroke engines. A quick home test is to have some one else pull the starter while your thumb is capping the spark plug hole, if it has enough pressure to push your thumb away compression is not the problem.

On a four stroke engine, there is a further option. Read the pressure as described, with the gauge, now squirt a small bit of oil into the hole, (maybe a sewing thimbles worth), slosh it around, reread the pressure gauge, if there is an increase this indicates worn out rings. No change means usually valve leakage.

Another simple check is to remove the cylinder head, (both type engines), raise the piston to the top and see if your fingers can rock it side to side, if yes your rings are worn out.

Hint; if your thumb testing, make sure your not in contact with the spark plug wire.

[EDDIE BUCK]

Originally Posted by moopups

Yes, compression is checked by inserting a rubber tipped gauge into the spark plug hole, and then the pull starter is activated a couple of times. The gauge registers the poundage that is present. Any engine with at least 60 pounds should at least start.

I am suspect that both engines are two stroke? Older two stroke engines often have a hard to diagnose problem. In that a two stroke's fuel is delivered via a scavenger port that is located in the cylinder wall from a pressurized crankcase, the crank seals at the outer ends often deteriorate over a period of years. The only way to correct the problem is to separate the two engine halves and replace the seals.

If the weed eater tries to start, maybe hits 4 or 5 times before quiting that is an indicator of failed seals. This applies only to two stroke engines. A quick home test is to have some one else pull the starter while your thumb is capping the spark plug hole, if it has enough pressure to push your thumb away compression is not the problem.

On a four stroke engine, there is a further option. Read the pressure as described, with the gauge, now squirt a small bit of oil into the hole, (maybe a sewing thimbles worth), slosh it around, reread the pressure gauge, if there is an increase this indicates worn out rings. No change means usually valve leakage.

Another simple check is to remove the cylinder head, (both type engines), raise the piston to the top and see if your fingers can rock it side to side, if yes your rings are worn out.

Hint; if your thumb testing, make sure your not in contact with the spark plug wire.

I had that problem a few years back. I tried everything I knew, plenty gas, plug firing. Even tried pouring a little gas in the sparkplug hole. Nothing I did would help. When you put a little gas in the plug hole,and put a plug that is firing in, It is suppose to try to start by hitting a few licks, still nothing, so I gave up and bought a new one and I was back in business. Then one day I was using my chainsaw and I noticed it was louder, the muffler was rusted mostly away. I thought the old weedeaters muffler would probably fit, so I went and took the weedeater muffler off. I could not believe my eyes, inside the muffler was what we call a dirt dauber nest, stopping up the exhaust.I forgot all about the chainsaw. I cleaned the nest out,put the muffler back on the weedeater, put some gas in it and pulled the starter cord twice, it started. Who would ever have thought that? Might be worth you taking a look. Sorry about the length of this post. Moopups gave you some very good info. This smiley is me when I FOUND THE DAUBER NEST

[doc623]

Thanks people.
Some things to try.

[bill not in oh]

Originally Posted by moopups

Hint; if your thumb testing, make sure your not in contact with the spark plug wire.

Very good hint... LOL

[doc623]

Checked the compression - would not move thumb from spark hole.
Heard of an old trick - add a small amount of oil into the cyclinder, replace plug and try starting to temp help compression to get it running - no help.
The trimmer motor is dead.
Contacted Homelite to buy a replacement motor/enging.
No luck.
You have to buy all the parts separately.
You cannot buy an entire engine - replacement engine wihtout the carb and perpherials.
Guess I am agong to have to look for another trimmer.
Any suggestions on brands.
Thanks.

[agmantoo]

Echo or Stihl
Both durable and used by ground maintenance professionals

[travis91]

i have a toro 4 stroke string trimmer thats a great machine...but there like $300 new... mine was free.

[Gideon]

That "dirt dauber" problem can get to be aggravating. They will stop up anything setting for long. Had taken the valve core from an inner tube recently and went to reuse the tire and the core was stopped up with mud. I check ANY hose, port, or small opening as a practice before installing. wc

[416LJT]

Originally Posted by EDDIE BUCK

I had that problem a few years back. I tried everything I knew, plenty gas, plug firing. Even tried pouring a little gas in the sparkplug hole. Nothing I did would help. When you put a little gas in the plug hole,and put a plug that is firing in, It is suppose to try to start by hitting a few licks, still nothing, so I gave up and bought a new one and I was back in business. Then one day I was using my chainsaw and I noticed it was louder, the muffler was rusted mostly away. I thought the old weedeaters muffler would probably fit, so I went and took the weedeater muffler off. I could not believe my eyes, inside the muffler was what we call a dirt dauber nest, stopping up the exhaust.I forgot all about the chainsaw. I cleaned the nest out,put the muffler back on the weedeater, put some gas in it and pulled the starter cord twice, it started. Who would ever have thought that? Might be worth you taking a look. Sorry about the length of this post. Moopups gave you some very good info. This smiley is me when I FOUND THE DAUBER NEST

Look directly into the exhaust tube coming out of the muffler. If the exhaust is plugged , your string trimmer ,or for that matter , any two stroke engine , absolutely will not start no matter what else you try.My string trimmer would not start for me and I did everything I could think of. Everything!!! By chance as I was looking the engine over , I noticed what appeared to be a plug of mud in the little exhaust tube coming out of the muffler. I figured that I had set the unit down sometime before putting it away and had jammed mud into the tube. I then took a small screwdriver and inserted it into the tube to clean the mud out. Guess what ? It wasn't all mud . A mud dobber wasp had inserted one of its larvae in there and then they cap that off with a small mud plug. A large white gooey mass ( the remains of the larvae I had just scrambled with the screwdriver ) came out. After that , one pull on the starter cord and that engine was running just like normal. End of story ? No. About three weeks after that episode was over , the exact same thing thing happened again. Now when it doesn't start right away , that is one of the first things I check is the exhaust. Wierd huh?

[416LJT]

doc623 and eddiebuck check this thread
http://www.homesteadingtoday.com/sho...71#post2289671

[Rocky Fields]

Hey.

Compression is best checked with a professional compression tester...one with different hoses that have a screw in end for each spark plug size. The hold over the hole kind often is hard to keep on the hole to get an accurate reading.

Spray a shot of starting fluid into the carb. It is more volatile than your gas/oil mix. See if that fires. If so, you have a fuel problem.

RF

[EDDIE BUCK]

Originally Posted by 416LJT

doc623 and eddiebuck check this thread
http://www.homesteadingtoday.com/sho...71#post2289671

Whew, I was thinking I was the only one in the world that has happened too. No telling how many has been thrown away for that very reason. THANKS FOR THE POST 416LJT

[416LJT]

Originally Posted by EDDIE BUCK

Whew, I was thinking I was the only one in the world that has happened too. No telling how many has been thrown away for that very reason. THANKS FOR THE POST 416LJT

Or how many people have been charged for a ring and carb repair that was never done.

You are welcome on the post eddiebuck. I thought you would be interested.

[Gideon]

Be careful with using starting fluid to start engines. I has absolutely NO lubricating qualities and can gauld your cylinder/piston. Lots of folks use mixed gasoline and a squirt bottle/can to inject it. When starting diesels in cold weather be careful not to use too much fluid as the engine may over rev and do damage to itself. wc

[retire2$]

2 stroke engines have a spark arrester in the exhaust. The arrester (which is a screen) gets clogged up from the oil/fuel mix. Clean, remove, or replace and see if this helps.