Need Help Troubleshooting Concrete Saw

Discussion in 'Mechanic and Repair' started by Georgiehopper, Oct 16, 2004.

  1. Georgiehopper

    Georgiehopper LawnSite Member
    Messages: 187

    We have a Partner Concrete Saw which has developed a problem and no longer runs unless you keep the choke on and the speed up very high. As soon as you lower the speed or let off the choke it quits.

    We've tried carburator cleaner and that didnt help. We also changed the airfilter and that made no difference.

    Any suggestions would be greatly appreciated!

    UNISCAPER LawnSite Bronze Member
    Messages: 1,426

    We have eliminated all but one Partner saw in our operations. Partner at one time made a great product, but, for reasons as you have mentioned, we got sick of them and went to Husqvarna, will never go back.

    The problem you describe may be two things combined. It could be the carb, and may be as simple as adjusting the low speed jet, or it could be a clogged jet. Will the saw idle down at all, or do you have to wide open all the time?
    You may have an idle speed adjustment that can be made if it will idle at all.

    More than likely, it is compression combined with a dirty carb. When we changed piston/rings and deglazed the cylinder bore, the problems we had that are similar to your saw went away. A two stroke engine has two types of compression they rely to run on. Cylinder compression, and crankcase compression, some call it crankcase presssure.
    The Partner saw is a piston port engine, loop scavanged, meaning when the piston goes down, the suction from it draws fuel and air into the crankcase for lubrication. As the piston begins to rise to the top of the stroke, the suction fills the crankcase with fuel/oil, swirls the gas vapors around and into the combustion chamber so it can explode and repeat the cycle all over again.
    If cylinder compression is lower than normal, it will adversely effect slower speeds and you will need more gas than air to get the engine to run because the heavier mass makes up for lost compression. The engine will also have to spin at a higher rate of speed to keep running because the charge from the lower compression is not as complete as the one from when the compression is correct. Basically, you are starving the engine for fuel by not having the systems it needs up and running as they should be.

    Try the simpler approach first, pull a compression check, and at the same time, remove the muffler and use a flashlight to see what the cylinder bore and pistion look like. If you see lots of scores on the walls, or scuffs and burning on the pistion skirt, you are due to rebuild the top end.

    One last thing. On the side of the cylinder on a Partner saw, there is a compression release for starting. Make sure that is functionong properly as if it is leaking someway, you will create the same problems I just mentioned.
  3. Georgiehopper

    Georgiehopper LawnSite Member
    Messages: 187

    Thank you for you very thorough explanation! The saw will not idle down at all. This saw used to run really great.... this problem seemed to develop suddenly.

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