026 wont rev to 12.5k+

[theoldfox]

Hi guys

I have an 026. Its recently had a new piston and head put on it and a new stihl 16"bar and chain (3/8).
It had a few teething problems with the carb and tank valve but those are fixed now.Compression is good and doesn't seem to have symptoms of an air leak. It starts and idles well, accelerates well and at WOT sounds and cuts well.
Problem is, I tacho'd it and only get 11.3k at WOT( out of wood). Ive tuned H by ear to just 4 stroke. It also has a moderate muffler mod (slotted about 20mm)
Any ideas why wont rev?? Do new bar & chains have friction that needs to bed in to free up. Would this cause 1000 rpm drop???

The 026 is quite old (guessing about 15years) and predates the de-comp bottom on top. What RPM should I expect from this saw??

Look forward to the comments

 

[blis]

The revs itself arent what you should be looking for, the key is right A/R and it determines how much it should rev...

so, in short if it runs good and 4-strokes a bit at WOT then its good...

 

[Fish]

Had a localguy call wanting me to order a carb for his 026, one with both adjustment screws, because his saw wouldn't rev fully, I said to bring the saw by, and I would look at it.
We sat it on the bench, and ran it with a tach, was about 11,000
or so.

While he was standing there, and the saw idling, I took off his air filter,
and the saw roared to 14,000 or so while I held the tach on it, while he was warching.

I asked him, "What does that tell ya?"""

He looked back, and said, "I, I, I don't know!!!!!!"





True story....

 

[timberwolf]

Once you get it fired up so you don't need the choke to start it try it without the filter, seen some filters on old 026's that pulled RPM down 2000 RPM.

Rereading I think fish was saying that,,, I'll second that then. depending on which 026 you have the newer 260 fiter may fit and certainly is an improvement.

 

[Fish]

His was just dirty, I told him to take it home and wash it gently with some
dishsoap, and it ran to his satisfaction after that.
The real danger is that if he had the fully adjustable carb, then he had gotten a new filter sometime in the future, or cleaned his old one,
then he would have had a real screamer, for a little while.

This guy is a pain though. He was commenting that the Stihl dealer
wanted over $90 for a new adjustable carb, and he wouldn't take it
back if it didn't cure his problem.

I said that I could get him one cheaper, but I wouldn't take it back either.

 

[Noko]

I killed my first chainsaw in that way.
I kept RPM by leaning H as air filter got old and dirty.
I cleaned the air filter, but it kept getting worse (passing less and less air).
When I put a new air filter, the saw ran too well and died.
I enjoyed about one hour of "race-like" cutting, though.

It was a good lesson, and I got infected with CAD by asking why and by taking the dead saw apart to see if I could fix it.

Noko

 

[litefoot]

I bought a crappy running 026 from a dealer for $50. He said that, although he hadn't looked at it closely, he figured the piston and cylinder were shot. I took it home and found a worn-out air filter plugged with crap. $20 later I had a great running saw. Now I guy in Colorado owns it and is happy as a lark.

 

[rupedoggy]

I just got a 066 that had a trashed big end rod bearing. When I removed the air filter cover a cup of dirt/sawdust fell out. I found the A/F totally plugged. Rebuilt with a used crank and went to start it. It would not. I found the high speed turned to 1/4 turn and the low speed about 2-3 turns. Good saw now.
The same logger has another ms660 and I tached it for him. 13,900 rpm. I think he just keeps adjusting the carburetor insted of cleaning the filter. Mike

 

[Fish]

Yes, I always preach against trying to adjust out any running problem,
it may alleviate the symptoms, but usually leads to saw damage.