Rebuilding Blown Echo PB620H

Discussion in 'Mechanic and Repair' started by ed2hess, Nov 22, 2012.

  1. ed2hess

    ed2hess LawnSite Fanatic
    Posts: 13,140

    This will give you a general idea of what is involved when you have a basic engine problem on a 2 stroke engine. The blower in the prictures is a PB500 but it is basically same as the 620. The 620H had a cracked ring and fragments ended up on top of the cylinder. The failure was a result of a crankshaft seal slipping out of place. Unfortunately the engine would still start so the crew ran it until it failed. The first set of pictures show the tear down.

    The picture of the piston was the actual 620H. YOu can see the damage to the piston. The next to last picture shows one way to get that flywheel off. I used a big screwdriver under the flywheel and a hammer to hit the center bolt. Some times that don't work.

    The last picture shows the 4 bolts behind the flywheel that have to be taken out to pull the engine apart.

    The tear down is pretty simple.

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  2. dstifel

    dstifel LawnSite Senior Member
    Posts: 919

    Can you do me a favor and take apart the throttle handle and show me what the inside looks like I swear I am missing something in their on mine throttle sticks and kill switch doesn't work
     
  3. Patriot Services

    Patriot Services LawnSite Fanatic
    Posts: 12,682

    Every time I've tried to rebuild something that fragged it usually isn't worth it in the long run. Sudden lockups put a lot of stress on cases and cranks. They distort or get tiny cracks and it only a matter of time before it let's loose especially in a crews hands.
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  4. ed2hess

    ed2hess LawnSite Fanatic
    Posts: 13,140

    This set of pictures shows the sequence for putting the unit back together. The only new parts were two gaskets, two crank seals, and two rings. Total cost $18.

    I put in two crank bearings, a piston, a bearing and pin for the piston . All of these parts were salvaged from seized machines at dealer. You can see some scuff marks on that piston on the skirt. I don't think that will be a problem since I have used ones before worse than this one.

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  5. Patriot Services

    Patriot Services LawnSite Fanatic
    Posts: 12,682

    Nice clean assembly habits you have there.
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  6. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    How does it run now...??
    I always polish the pistons with a small wire toothbrush..using a side to side motion.
    If there are any scratches in the piston they should not be in line with the stroke...
    Fine scratches paralell with the rings will hold a small amount of fuel that will cushion the piston from digging into the cylinder..just like crosshatches on a cylinder...
    If I can remember...I will post a pic of the process on Monday ...it makes them look like new..
     
  7. Patriot Services

    Patriot Services LawnSite Fanatic
    Posts: 12,682

    Remember when knurling skirts and guides was considered acceptable practice.
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  8. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    It was a dark time in modern mechanics...nothing like turning your pistons into cylinder hones...
    I bought an old chevy pickup with a 308 ci 6cyl that had a knurled piston in it.
    It hourglassed the cylinder and snapped the rod...I couldn't find a replacement so I pulled the.pan..pushed the piston up to the head..and shoved a rag up into the cylinder to make sure it wouldn't hit the crank...ran it for another year...they don't build them like that anymore..
    In my own defense...I was a 19 year old mechanic at the time...and the engine did still run.
     
  9. ed2hess

    ed2hess LawnSite Fanatic
    Posts: 13,140

    These are the last steps in getting it going. In the first picture I show gluing those washer in place before mounting. I noticed that big wear groove on that carb lever when I went to put it on. Had to replace that. The unit started on the third pull and I let it run at low rpm for awhile. I put in extra oil in gas. I have run it about 30 minutes a couple times since rebuild. This is my 5th blower all PB610/620 series. I have 7 back up blowers for our business so I am going to shut this off for awhile.

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  10. ed2hess

    ed2hess LawnSite Fanatic
    Posts: 13,140

    Well here is the device in the two positions of off and on.

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