mainewoods
Addicted to ArboristSite
Which raises a lot of questions - such as what makes them crack? The heat generated from the cutting causing the metal to become fatigued, or the port job causing added strain on the piston, for example ?
Yesterday's Project: Husky 55 Air Injection Rebuild/Porting
- Thread starter blsnelling
- Start date
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Mastermind
Work Saw Specialist
I'd say it's the holes in em Clint. 
mainewoods
Addicted to ArboristSite
Ahhh, never thunked of that one.
I'm glad you said it Randy, the idea of cutting holes in anything that wasn't cast or forged to have a hole there has never sat right with me, throw in multiple heat cycles and it should just be a matter of time.
Naked Arborist
Hack from way back.
If your going to open the windows in a piston you'll need to do some polishing and some heat treatment at the end. You have got to relieve the stress risers form the casting created by a sutle but new stress area.
Here's the piston in my 55.
I went back in to open up the lower transfer ducts to the case. This idea came from Stihlbro. With this modification, windows would not be needed in the piston.
Brad all you had to do was see how 1 of the 2 types of 590 topends were made. I have a thread on them.
used 590 piston
used 590 piston
Doesn't that just makes it an open port top end again and defeat the purpose of the whole exercise?
edit: Nevermind. I just read the other recent 55 thread with everyone's input on the subject and I guess the answer is crystal clear....sorta.
http://www.arboristsite.com/community/threads/hard-time-finding-the-right-piston-husky55.249742/
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mweba
Addicted to ArboristSite
No. The divider is still there below the transfer ports. This is now very similar to many Stihl cylinders.
See my edited post above...
Great stuff in that other thread.
Great stuff in that other thread.
stihlbro
ArboristSite Operative
It's not my idea, I didn't create it, design it, or even claim any step of it. Someone out there has already done it before. I just shared what worked for me.
Joey
Brad to show folks they dont know what they are talking about on making a closed port into a open port going backwards. 
My race MVP 166 bridge was removed to make it open port and my MVP copied cylinder on my partner 5000 you ran against and maybe ran had bridge removed to make it open port too. They ran pretty dang good didnt they.
My race MVP 166 bridge was removed to make it open port and my MVP copied cylinder on my partner 5000 you ran against and maybe ran had bridge removed to make it open port too.
They ran pretty dang good didnt they.
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troylee
ArboristSite Guru
Saw is still running great to this day. 50 plus tanks of fuel. 32:1
That's always good to hear!
