No Compression on Chainsaw Engine - HobbyTalk
 
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post #1 of 6 (permalink) Old 07-29-2004, 01:05 PM Thread Starter
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No Compression on Chainsaw Engine

After much fussing, I found my Poulan 2775 Chainsaw will not start because there is inadequate compression. Looking at the exhaust port, there appears to be scoring on the piston. There is no significant carbon buildup, however.

Is it possible to repair by honing the cylinder and moving the radial position of the piston ring?

Should I replace the piston and ring?

Must I replace the cylinder (probably will through the unit away in this case)?

Any other ideas?


What could cause the scoring / loss of compression if there is no carbon in the exhaust port? I was using a slightly rich oil mix (32:1, 40:1 recommended). The engine would rev up momentarily when gas ran out of the tank and the air/fuel mix ran lean. But this would only be for maybe five seconds.


Jack Hitt
Crestwood, KY
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post #2 of 6 (permalink) Old 07-29-2004, 03:04 PM
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There really is no way to hone out the scoring. The ring can not be rotated because it is fixed in place by a pin. The only real fix is to replace the piston and cylinder. Parts are about $50 if I remember correctly. If you have been running the correct fuel mix then the most likely reason is dirt being sucked into the cylinder.

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post #3 of 6 (permalink) Old 08-31-2004, 12:07 AM
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I'm gonna jump on this thread ride...I have a similar problem. I bought a Craftsman 46cc 20in chainsaw about 2 years ago. I used the 2 cycle oil in the box it came in. After one tank of fuel and about 5 minutes on the second tank, it locked up. I took it back to the store and the salesman promptly gave me a new one. I thought this is great. Well two years later and many, well not many tanks of fuel later my chainsaw has done the same thing. I let it cool off and it started right up and ran hot until it froze up again. I tore it down to see that my cylinder is also scored. I really don't think that it is the fuel because, I run the same fuel out of the same gas can on my string trimmer and my leaf blower with no problems. I am at a loss as to why this would happen. I have never taken the air filter off of either of the chainsaws so, I don't think that it was debris getting into the intake. Is this a coincidence or did I get hold of a bad lot of chainsaws. I can't take this one back because the warranty has expired. I guess I'm gonna go with the $50 repair route because it is $200 new. I would just like to know why it overheated. Thanks for any info on this.
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post #4 of 6 (permalink) Old 08-31-2004, 12:09 AM
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One other thing. Are Craftsman chainsaws using Poulan engines? I have looked everywhere and cannot find any info on the matter. Thanks again.
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post #5 of 6 (permalink) Old 08-31-2004, 03:19 PM
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Craftsman chainsaws are made by Poulan. My guess is the engine was running lean. With the way emission standards are, the engines are tuned, IMHO, too lean. Mix the fuel a little heavy on the oil, maybe 32:1 instead of 40:1 and turn the highend needle out about 1/8 to 1/4 turn and those problems should go away.

Problem is, the manufacturer can't tell you those things...

If your saw is out of warrenty then the cost to put in a new piston and cylinder would cost close to the replacement value... somewhere around $150.

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post #6 of 6 (permalink) Old 08-31-2004, 05:07 PM
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Thanks for the advice Hankster. I appreciate it.
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