Help with 029

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stihl025

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Since I don't want to hi-jack some other post, I figured I'd start my own for this.

As stated is some other threads, I am doing a little work to a buddy's 029. He never did any maintenance to it, just spark plugs, bar, chain, etc.

We were out cutting one day when it began to bog down in the cut. Reving it with no load, it was fine. We cleaned the air filter, changed the spark plug, and changed the fuel filter (which was never changed in 13 years). It ran okay, but still not great. Brought it home with me. Tore into it and found some very small cracks in the fuel line, impulse hose. Carb was full of crud. Replaced the hoses, got a rebuild kit for the carb, and cleaned the saw up. Did a muffler mod as well. Didn't go outrageous, just an two more 5/16" holes. Put everything back together, set the carb screws back to factory (1 turn out) and proceeded to fire it up. I am having trouble getting it started. I choke it, it turns over. Flip the choke off, and it wll run for 2 seconds on the throttle lock setting and die. Get it to idle for a few seconds but can't get it to throttle up. It bogs down. Try a few different L settings to help with starting, but can't find something that works. Still hard to start, will fire with choke on, bogs when throttling up. I "sometimes' can feather the throttle to keep it running, but not for long. I have taken the carb back off and re-cleaned the entire thing, thinking maybe I missed some dirt. Particles were so small and few, that I couldn't tell if they came from the carb or the workbench. :dizzy:

Same deal even after the carb cleaning. I am at a loss. The saw at least ran when I brought it home, now I can't keep it running... Help.
 
Pull the muffler and check the piston for scoring.....the carb being plugged likely caused lean running and piston damage
 
Okay. Let's see. In the other post... Hmm, I should just cut and paste. It would be easier.

Anyway, piston has some scratches on it, but only the exhaust port side, no scratches on the cyl. walls, only normal wear.

Compression cold before starting it up with al the new stuff = 140
Compression hot = 110
Compression cold again, just now = 130

As for the carb settings, factory 1 turn out on each to start. I would have thought it would have fired right up, even with the basics.
 
Just a thought and I have done this myself.

When putting the carb back on the impluse hose would not hook back into the bottom plate of the carb. It would be sitting beside it. Kind of makes since of this starting problem. Something easy to look for.
 
Go back into the carb, take it apart, remove the lever/spring/needle,
and blow out that passage, and hold it up to a light and verify that it is
clear, then re-assemble.
 
Ummmmm did you just drill holes in the muffler can?

If you did you likely are suffering from true suck back as everybody likes to laugh about
 
Okay, this could be a novice mistake, but I used carb/choke cleaner with the little plastic hose to blow out the passages. Could that not be enough pressure to really get the junk out? It seemed to have squirted through the carb, but then again, it is a messy way to do things. I really checked for debris in all of the little holes, BUT.....
 
029 problem.

Depending on how deep the scoring is on the piston it may be the problem. When you pull and look at the far wall ( intake side of cylinder ) and say there isn't any scoring thats because 80-90% of scoring in a saw is on the exhaust side and yes you can assess the piston wall on the exhaust side but its difficult to see the exhaust cylinder wall, try a light shone down the spark plug hole with muffler off. Also where is the carb inlet lever height set at?? Some pic's of piston would be nice as well as carb inlet lever. Is it the correct kit for that carb??
 
Ummmmm did you just drill holes in the muffler can?

If you did you likely are suffering from true suck back as everybody likes to laugh about

Two holes in the front, right in the middle of the depression... Should create a straighter path for the exhaust. Explain the "suck back".

Wooo, I have so much to learn.
 
Any thing inside the muffler can almost invariably will end up back in the combustion chamber so...

If there were any metal bits left over from the drilling you have at least junked the piston...

you will need to short block it or tear it down
 
Okay, this could be a novice mistake, but I used carb/choke cleaner with the little plastic hose to blow out the passages. Could that not be enough pressure to really get the junk out? It seemed to have squirted through the carb, but then again, it is a messy way to do things. I really checked for debris in all of the little holes, BUT.....

.. some (all later) carbs have low speed circuit check valve that is NOT replacable... Stihl recommends that you do not use carb cleaner for other than exterior uses.; just brake cleaner for interior uses.

However... at 110, your saw sucks... Did you fry the cylinder?.
 
Any thing inside the muffler can almost invariably will end up back in the combustion chamber so...

If there were any metal bits left over from the drilling you have at least junked the piston...

you will need to short block it or tear it down

Muffler was off when drilling, and I did make sure there was no metal filings left in the muffler.

I do need to make a correction. I used brake cleaner, not carb cleaner to blow through the carb.
 
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