# Compression ?



## Cmarti (Feb 18, 2009)

I compression tested a 1 year old craftsman blower model 358.794760. and it was 75. After taking it apart and cleaning the piston and cylinder, a coating of oil, and tightening the muffler bolts it is 80-82. By comparison, my Echo is 125 to 130.

I noticed no scoring or gouges on the piston and cylinder wall. Only minor carbon build up removed with WD-40 and a nylon pad used to polish stainless. Ring is in tight and not broken. How could the ring wear down in only a couple uses? I guessed carb and must be wrong with this compression. I will try a new ring. I would appreciate any tips, suggestions and thoughts on what went wrong. Thank you in advance.


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## bsman (Jan 22, 2006)

its craftsman. look on the side and you may find a DURABILITY PERIOD of only 50 hours some times. the metals used there will be lesser quality of that in your echo or a stihl. It could also have a small leak somewhere too,


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## hankster (Jan 1, 1998)

Is the ring stuck? did you put the piston back in in the proper orientation?

Note: The 50hr. durability is for emissions.... federal law requires emission be met for a minimum of 50 hours.


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## Cmarti (Feb 18, 2009)

hankster said:


> Is the ring stuck? did you put the piston back in in the proper orientation?
> 
> Note: The 50hr. durability is for emissions.... federal law requires emission be met for a minimum of 50 hours.


I am not sure what you mean by stuck. The ring is in the groove with no visible cracks or breaks. It seems to have a tight fit in the cylinder. I am not positive on orientation....oops, I took it all the way down and cleaned the cylinder, piston and carbon around the ring. the piston only goes back on the crank two ways. Is there a way to tell what is the right way? The gasket at the base of the jug looked fine.

I did not know if a ring and new gasket would help? It is a 10$ experiment.
Sorry, I know.......rookie.

Thank you for the consideration.


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## Cmarti (Feb 18, 2009)

I did a search, and Hankster, LMtech, bugman and others must be tired of the questions on 25CC Craftsman. My appologies. I believe the ring is stuck (no movement) I will heat it and clean the groove and replace it. I will report back on my rebuild:thumbsup:

Thanks for all the help. I have been lurking using your guys advice for awhile.


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## hankster (Jan 1, 1998)

When you put it back together, the ring gap should be close to the intake port... when assembled you should be able to read the writing on the rod bearing that attaches to the crank.

What happens is the ring and cylinder seat (wear in to each other) when run. If you assemble it backwards then what it was before, it may not be seated properly since the wear may not be the same all around the cylinder.


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## paulr44 (Oct 14, 2008)

hankster said:


> When you put it back together, the ring gap should be close to the intake port... when assembled you should be able to read the writing on the rod bearing that attaches to the crank.
> 
> What happens is the ring and cylinder seat (wear in to each other) when run. If you assemble it backwards then what it was before, it may not be seated properly since the wear may not be the same all around the cylinder.


I'd ask how you know that you'll see the imprint on the rod bearing, but I know the answer and I feel for you. Tough working on the craftspeople stuff....
Paul


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## hankster (Jan 1, 1998)

You get used to it  I can rebuild one start to finish in 20 minutes. Gets easy after a few thousand times.


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## Cmarti (Feb 18, 2009)

I picked up a ring from my local dealer. Put it in with the gap to the intake, and used a strip of plastic as a compressor, and coated it all with oil. Ran like a champ. BTW the C1U carb was closer to 1 out on the needles, than 1.5 to 2. I have it just leaned off 4 cycling. I wanted to err rich. 

Hankster and guys, thanks for all the help. It was fun to learn something new. 
One last question, what would cause the ring to stick with so little run time?


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## paulr44 (Oct 14, 2008)

hankster said:


> You get used to it  I can rebuild one start to finish in 20 minutes. Gets easy after a few thousand times.


You're hired. When can you start!? Good 2-stroke mechs are hard to find.
Paul


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## hankster (Jan 1, 1998)

cmarti, most likely the carb was a bit out of adjustment (lean) and caused the oil to overheat and bake to the piston/ring. They have to really lean these old design motors out so much to meet emissions that it doesn't take much to make them too lean.

paul, funny, most don't like to work on 2-cycles, I hate working on 4 stokes. Just so used to it that they are pretty simple now. I do have a headache unit once in a while but it's few and far between. Been doing 2 stokes exclusively for close to 6 years now, this past winter (when laid off for seasonal slow times) I figured it out and have worked on over 10k units! Yikes, even scares me!


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## paulr44 (Oct 14, 2008)

10,000 units, eh? Well, I fixed 1,000,000 units last year alone. LOL. I lost count back in the 80's, but know what you mean.

Hank, I'm serious - need winter work? I know, you're up in the hinterlands. Back in the '90's when I ran a shop with 10 mechanics, I got to the point where during prospect interviews I'd ask just 3 questions(in person), one of which was "if a 2-stroke ran seemingly quiet, would not run up to speed, what would you suspect?" If someone couldn't answer "clogged exhaust," I'd forego their application. A stupid-simple question for someone with any experience, but basics is what it almost always comes back down to....can't plug a OBD II computer into them, so ya' gots ta use yer noggin!
Paul
Holding our own in N.J.
P.S. If you ever get to Frankenmuth think of me...I loved it when we'd on the way to visit my sister in Ellsworth.
P.P.S. If you get to Cass City, visit Walbro, ask for Luis and tell him I say hi - he's a great guy.


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## hankster (Jan 1, 1998)

Actually I plan on the winter break. Nice to have some time off and old enough to know how to enjoy it.  Sort of like a teacher, just get the time off in the winter instead of summer.


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## hankster (Jan 1, 1998)

Did just get a new count from my stats page. I'm now over 15k units completed over 7 years. Total months actually worked is 63 considering I get about 4 months off a year during the winter.


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## pyro_maniac69 (Aug 12, 2007)

thats mind boggling, I think I might only go through a 1000 per season

1000 lawn mowers
1000 snow blowers

man I need to get a job like hank


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## kpring (Oct 11, 2009)

hankster said:


> cmarti, most likely the carb was a bit out of adjustment (lean) and caused the oil to overheat and bake to the piston/ring. They have to really lean these old design motors out so much to meet emissions that it doesn't take much to make them too lean.


I have found this problem on a couple Craftsman leafblowers that I picked up at our landfill recycle center, I was able to get the ring unstuck and they work for the rest of the season but eventually same thing happens and then because I don't really know the best way to get them unstuck (I pry them out and have broken a few rings doing this). This just happened to my Craftsman chainsaw and I just replaced the cylinder/ring/piston last year (last time I put money into any Craftsman 2 cycle). Questions that need answering: What is the best way to free up a stuck/carbon gummed up ring so I don't break this ring, and you say that it is the adjustment is too lean causing the oil to bake on, is there an adjustment to make I can do (I'm not too concerned about emissions:devil so this won't happen again, (or at least til next year).


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## hankster (Jan 1, 1998)

I find that applying some heat to the piston/ring can loosen it up enough to remove the ring. Open up the high end needle on the carb 1/4 turn to richen it up a bit.


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