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Echo PB-650 having odd full throttle problems

Discussion in 'Mechanic and Repair' started by genesis215, Apr 12, 2010.

  1. genesis215

    genesis215 LawnSite Senior Member
    Messages: 795

    I have a 2003 Echo PB-650 that's been having issues all of a sudden. It starts up with 1 or 2 pulls, and idles great, but it has very erratic operation at full throttle. It kind of sputters and shakes, and sometimes it's randomly cuts out almost, and then goes back up to somewhat normal, but not the full screaming sound that it normally has. The muffler has practically zero carbon, and the spark plug looks normal, with only light tan deposits. Also the fuel filter was just changed. It sometimes doesn't do it, but it seems to do it the most when it's hot outside. I tried taking off the gas cap in case the tank wasn't venting properly, but that didn't affect anything. I am using Shell 93-octane gas with Amsoil at 50:1, and 1 oz. of Seafoam per gallon. All my other stuff runs great. Any ideas?
  2. genesis215

    genesis215 LawnSite Senior Member
    Messages: 795

    Bump. Any ideas at on what might be going on? It seems to do it only when it's above 75 degrees out, and when it gets up to about 85 it won't hardly get up to half throttle.
  3. morgaj1

    morgaj1 LawnSite Senior Member
    Messages: 318

    Have you checked the coils? Might be a spark issue.
  4. genesis215

    genesis215 LawnSite Senior Member
    Messages: 795

    No I haven't, but that kind of sounds like it since it only does it when hot out. I don't know exactly how to check the coil, could you tell me how? Thanks.
  5. morgaj1

    morgaj1 LawnSite Senior Member
    Messages: 318

    Here is a good You Tube video showing how to test the coil on a chainsaw. If it shows good spark when cold, wait until it starts dying and test it again. If you find that it is the coil, get the dealer to replace it. Echo has a lifetime warranty on coils, and I am assuming they did in 03 as well. Hope this helps:

  6. genesis215

    genesis215 LawnSite Senior Member
    Messages: 795

    Well guys I've checked the coil, and it is fine. I disconnected the kill wire like in the video, didn't change anything. I am wondering if it is the tank vent, or even a fuel line. What do y'all think?
  7. morgaj1

    morgaj1 LawnSite Senior Member
    Messages: 318

    Try this - Crank it and run it until it starts sputtering. While it is running, take the gas cap off. If it clears up and runs fine, then the gas cap vent is bad.
  8. Merkava_4

    Merkava_4 LawnSite Bronze Member
    Messages: 1,334

    Echo says you have a Walbro WYK-150 carburetor. The Walbro manual shows a high speed mixture needle on the side; do you see one on there? It'll look like a screw head with a spring under it.
  9. markahurley

    markahurley LawnSite Senior Member
    Messages: 252

    i had the same thing happen on mine. kept dying out at full power--and got worse and worse. mine ended up being a carbon build up on the exhaust screen. you can take the screen off, or if yours is like mine was and is too rusted to remove the screws, just punch a few holes in the screen. with the carbon build up, it can't breathe, and will choke itself out.
  10. ed2hess

    ed2hess LawnSite Fanatic
    Messages: 13,846

    I got two of them older than yours....mine did the same thing and I had to get an adjustable carb and that fixed the problem. I tried everything including putting new seals on crank shaft. In the early years NO adjustment on the units. I guess you tried it with exhaust off and ports are clean...usually those units never had carbon problems. I even pulled the head and checked those transfer ports and they were good to go. I didn't test compression put I bet these units are running pretty low due to wearing down the rings and sleeve surface....

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