Small Engine Repair: Compression Test on a 2 Stroke Craftsman Chainsaw



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**Always follow the instructions in your repair manual when doing repair or maintenance work on Outdoor Power Equipment. Manuals can be found at the manufacturers website.**

When you check cylinder compression on a gas engine you should have the throttle wide open, Choke open, and ignition kill switch off. In this video I check the compression on a Craftsman Chainsaw.

Thank you for watching!

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12 thoughts on “Small Engine Repair: Compression Test on a 2 Stroke Craftsman Chainsaw

  1. If you don't have a service manual is there a general rule of thumb of acceptable pressure ratings for trimmers, chainsaws, etc?

    BTW, thanks for the videos, I've subscribed not too long ago and appreciate the information! Keep up the good work!

  2. Good tip on the on/off switch, I know not to leave plugs un-grounded on older outboard ignition systems, but never thought about it on chainsaws etc. I also wondered if the length of a compression tester hose made a difference on how many pulls? guess not, great video's

  3. Looks like that's a Harbor Freight compression tester? If it is I've bought 2 and get any of my good running saws above 30 psi. Do you like that gauge?

  4. Blowers and trimmers needs at least 75psi to start below than that will not start. For a accurate reading ,except for the stihl, you must pull as many times as soon as the needle stop.

  5. Thanks for the video.  I had forgotten to hold the throttle open, so I repeated my test.  Didn't make any difference; 100 psi after 5 pulls.  Tried 5 more, but stayed at 100 psi.  The saw was cold; I hadn't used it for about a month when it quit because of a bad fuel line.

    One caution:  I had to use an adapter on my compression gauge.  Fortunately, I pulled gently on the rope the first time and the piston hit the adapter.  If I had pulled hard the first time, I could have damaged the piston.  I noticed that yours reached into the cylinder about the same distance as a spark plug.  I cut mine off to about that same length.

  6. I just tested my Poulan 2450 cc engine.  It's supposed to have 125-145 psi, but mine maxes out at 60 psi.  Is this a shot engine, or would it be worth putting in a new piston ring to try to fix it?  Or should I consider a new piston and cylinder head too?

  7. Hey thanks much, the comments section filled in the blanks too, like whats the bare minimum of compression needed before an engine will start, and that's 75psi – 90 is a worn out engine. 120 -145 psi is best. anything really high could be carbon buildup on top of the piston causing pre-detonation.

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