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Husqvarna 550xp pop up

Discussion in 'Chainsaws' started by WoodsliverDan, Dec 4, 2018.

  1. WoodsliverDan

    WoodsliverDan Mechanical Beaver Builder

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    So, after doing some research and not finding much on making a pop up piston for the 550xp, I have decided to make one to try and post my results. After measuring the squish, (with gasket) and finding it to be .030" I have decided to turn .030" off the base of the cylinder and .020" off the piston. This should put me right at .020" squish with gasket. I hope to have more time this week to turn the base and possibly reassemble saw for a test drive this weekend.

    I have decided to do pop up vs squish band cut due to the fact these pistons are so heavy! Figured they could use the diet??! Anyways, I think dropping the cylinder with the pop up should give me pretty good timing numbers as well. We'll see :)
     

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  2. WoodsliverDan

    WoodsliverDan Mechanical Beaver Builder

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    So tonight at work I had a chance to turn the base on the cylinder. I took .030" off both the base and the cylinder skirt. I have a new piston ring and circlips ordered which should be here Friday. Stay tuned.
     

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  3. WoodsliverDan

    WoodsliverDan Mechanical Beaver Builder

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    I have been asked if I'm going to make a stock saw for comparison. What does everyone say? I have another 550xp laying around I could use.
     
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  4. WoodsliverDan

    WoodsliverDan Mechanical Beaver Builder

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    Awfully quiet in here. Suggestions on ignition timing advance?
     
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  5. huskihl

    huskihl Sausage Fingers Forever

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    It'll be snappier and probably cut faster. But the autotune may not like it.
     
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  6. WoodsliverDan

    WoodsliverDan Mechanical Beaver Builder

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    Have you tried it?
     
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  7. huskihl

    huskihl Sausage Fingers Forever

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    Using the popup, your exhaust and transfer timing will only change by a degree or so. Your intake timing went up by about 2°
     
  8. huskihl

    huskihl Sausage Fingers Forever

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    Yes
     
  9. Red97

    Red97 Mastermind Approved!

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    Won't hurt a thing to have a baseline to compare against.

    Never been in a 550 so not sure what they like.
     
  10. WoodsliverDan

    WoodsliverDan Mechanical Beaver Builder

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    I'm confused. You said the autotune may not like the advance. Have you done timing advance on a 550xp or not?
     
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  11. WoodsliverDan

    WoodsliverDan Mechanical Beaver Builder

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    Yes, close
     
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  12. huskihl

    huskihl Sausage Fingers Forever

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    Yes I have.
    It cut faster with the advance, but seemed to have a hesitation while accellerating. Not sure if it was due to the AT system not being calibrated or needing an update or not. That hesitation bothers some folks, others not so much
     
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  13. WoodsliverDan

    WoodsliverDan Mechanical Beaver Builder

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    Ok thanks. How was the heat? Not looking to make a cookie cutter, rather a saw that will burn a gallon of gas a day.
     
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  14. huskihl

    huskihl Sausage Fingers Forever

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    The AT seemed to allow enough fuel to compensate for it. But I wasn't burning tankfuls at a time looking for it either. No pinging or loping after long cuts
     
  15. huskyboy

    huskyboy Sorta a Husqvarna guy.

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    I found my 562 responded a bit better to advance than the 2253 (550). Both gained torque from it though. Make sure you copy that cooling slot in the topcover the new saws have if yours don’t already have it. Gut the muff as much as you can. It’s worth the temperature reduction.
     
    Last edited: Dec 7, 2018
  16. WoodsliverDan

    WoodsliverDan Mechanical Beaver Builder

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    Half the key a good starting point?
     
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  17. mdavlee

    mdavlee Hillbilly grinder

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    If you’re talking about mine we used it pretty hard in the end of May logging. Never had a problem on 90 degree days
     
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  18. huskihl

    huskihl Sausage Fingers Forever

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    I'd start at about 1/4 of the key. About 1/4" of movement at the perimeter of the fw. If you like it, take another 1/4 of it and try it again
     
  19. huskihl

    huskihl Sausage Fingers Forever

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    Yours acted the same way up here. You mentioned it not acting up at all for you. Difference in the fuel, oil, temp, humidity....
     
  20. mdavlee

    mdavlee Hillbilly grinder

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    It is odd but al those changes do affect it. The timing wasn’t too bad for me. It ran awesome as is.
     
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