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#Post#: 90144--------------------------------------------------
How does this piston mod work?
By: joe_indi Date: August 10, 2023, 10:25 pm
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I tried this first on at least four FS55 trimmers, then on a
after market MS460, yesterday on a MS180 and an old FS200
brushcutter.
My intention was to increase squish without touching the
cylinder. Also ground about .3mm from exhaust port to advance
the exhaust , opened muffler slightly to give less resistance.
Only issue was an oily exhaust deposit. But since I was using
25:1 fuel, I tried 50:1 which cleared out the exhaust.
The result of this mod was very quick throttle response and
power output and the trimmers and brushcutters are hitting their
speed limiter range very rapidly. On the 460 and 180 there is an
increase rpm at WOT.
Since my mechanical skills are only practical not theoretical I
wanted to know what was the reason.
And what I did was very crude (evident from the photo), since I
just used a dremel
#Post#: 90148--------------------------------------------------
Re: How does this piston mod work?
By: Chainsawrepair Date: August 11, 2023, 6:46 am
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Reasoning for wanting bigger squish was? Just guessing due to
gas octane quality there?
No clue on anything else beside making the piston lighter a bit.
#Post#: 90357--------------------------------------------------
Re: How does this piston mod work?
By: joe_indi Date: December 13, 2023, 11:17 pm
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Sorry for the delay in responding.
Over the past few months my browser kept popping up warnings
when ever
I tried to access his forum as well as Forestry forum
To answer your query, yes, with E12 i was trying out various
remedies for over heating and a knocking sound that sounded like
Piston slap or a worn con rod. But these went away when I
increased squish on the piston.
About 0.3 mm . Tried on the lathe but this burring seems to
increase the surface area more
And the engine runs smoother, though a bit ' throatier'
During my experiment i could afford a new piston if things
turned wrong, cheaper than a cylinder.
After the initial positive effects i have done this for
customers who brought in their brand new 382s and 462s for any
precautionary work i could do to prevent breakdowns from fuel
related issues , E fuel that is.
We will be going to E20 next year or in 2025
#Post#: 90358--------------------------------------------------
Re: How does this piston mod work?
By: 3000 FPS Date: December 13, 2023, 11:29 pm
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Wow sorry to hear that about the E20. That has to be hard on
some of the older saws that were not designed for it.
Here I am making smaller squish on my saws, and you have to make
the squish bigger.
I think some of the old Poulan contervibes have a squish that is
around 030". I wonder how those would perform on E20.
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