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Echo PB 650 died, need diagnosis help

Discussion in 'Mechanic and Repair' started by brucec32, Oct 28, 2006.

  1. brucec32

    brucec32 LawnSite Platinum Member
    Posts: 4,403

    I have an Echo PB 650 that has run strong until last week when it cut out suddenly and died within about a second's time. When I attempted to restart the cord would not pull and I set it aside and used another unit.

    I took a look at it today, removed the starter assembly and noticed a small piece missing out of the "cup" inside the crank assembly, but could find no missing metal.

    I turned the crank by hand and after a little sticking it would rotate. I reattached the pull cord assembly and tried to fire it up. It does pull smoothly now even with the broken cup inside.

    No luck. It seems like there is not as much compression as it needs (sound and lack of resistance). I checked the plug and replaced it, then tried again. It definitely gets a nice spark, but won't start or even hiccup.

    I checked the compression and it is 60psi, which I suspect is low. I don't have the specs on it, however.

    The unit is about 5 years old so I'm not looking to dump much money in repairs into it, but if anyone has an idea what to look for I'd appreciate the help.

    I have run multiple other 2 cycle equipment with the same fuel for a few days so I doubt low oil in the mix is the culprit. It did run very strong till it suddenly stopped, so it's not the gradual wear you see with age.
  2. Jason Pallas

    Jason Pallas LawnSite Bronze Member
    Posts: 1,325

    Sounds like you blew a ring. But first - make sure the carb is nice and tight. I've had the mounting bolts loosen up and if you don't notice it, you can go down the wrong path as far as chasing the prob.
  3. ed2hess

    ed2hess LawnSite Fanatic
    Posts: 13,204

    Are you pretty sure that head gasket is okay.....I would replace that first and that would give you a chance to look at rings and cyclinder for scouring. I had to replace the head gasket on both of my PB650 units. Another possibilty would be cranshaft seals....you can check the one on the starter puller side easy when you do that repair.
  4. lawnmaniac883

    lawnmaniac883 LawnSite Silver Member
    Posts: 2,613

    60psi = internal damage.

    Tear the block apart and see what you find. 2 strokes are very easy to get into.
  5. J&R Landscaping

    J&R Landscaping LawnSite Fanatic
    Posts: 5,096

    That engine should have 140 psi or there about. Are you sure you 2 stroke mix was correct?
    You might consider pressure testing the unit to determine if you have a bad top end gasket. I would also check the insulator block as someone else mentioned.

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