Mod'ed MS441, It can be done.

[Al_Smith]

Misunderstood ,not piston to head deck clearance commonly called squish but rather piston skirt to cylinder clearance .

On that 200 psi that's somewhere around 20 thou head deck with a pop up  and some tricks  ;)My gauge could be off a little too for that matter but it pulls over about as bad an older 066 without a decomp valve . You think that's a big deal,it's not really . I know a 3 cube alkie burner that's upwards of 300 static .

Now you do a little reading though and most folks back them off to around 190 static and they've achieved much higher than 200 .

[Cut4fun]

Say though since evidently you assembled the saw ,if it's not some great secret how much piston to cylinder clearance does it have ?

I knew what you were asking Al. He came back with squish instead 

[441FELLER]

sorry for the misunderstanding, i was actually kinda scared about the side clearance, being that diff metals have diff expansion rates when hot. but when i gave to kid specs my intentions were to have the clearance be .005", just because i was told the more slap, the more sound, i know the standard is usually .003" and under, i figured that if it EFF'd up i would just jug it and go bigger, so i put it all together and so far so good.
So what are your thoughts Al?, you think this die kid is blowin' smoke? seeings how it didn't swell, melt or start pushing piston pancakes out the exhaust?  at any rate, i spend no cash on the piston, so at least i'm not out big bucks for false merch.

[tlandrum]

my 460 is setting at 195 with a pop up and milled jug and 22 squish. should have milled it down a hair more but it runs ok.he he its had a few things done to it, but hey its not got a fancy piston like that 441 does  just a stock slug nicely cleaned up. im with ya al_smith i think hes yanking our rope. and oh yeah i run 93 octane,no av gas. it dont like that stuff

[Al_Smith]

So what are your thoughts Al?,  .

To be quite honest I have no idea .Not knowing the difference in thermal expansion ratings between this alloy and the standard aluminum and  I assume hard nickel Stihl cylinder .

When I made an iron cylinder for a 125 Mac I set it up for standard Mac saw clearances of 4.5 thou .Had it been to kart specs it would have been 7 thou . Those are aluminum pistons and cast iron liners but running a couple thousand RPM's faster .I suppose though that the diameter would play a factor in it as to size  for clearance .If it doesn't hang it must be okay .

[Al_Smith]

al_smith i think hes yanking our rope. 

Well ya never know  Maybe so maybe knot .No matter though it's entertainment .

[441FELLER]

the saw i guess is kinda fancy....don't ever be afraid to try new stuff, that's how the best stuff becomes better.  fancy is good, muff mods, ignition mods, carb retrofits, internal deletes/updates, shroud trims, sprocket swaps, are they necessary? of course not. but we all do it for one sole purpose, because we're all crazy about saws and pushing their limits.

So here's to all of us and our "Fancy" saws.

[Al_Smith]

Well now the big question is with all this turbine blade piston ,go faster muffler bolts,super duper muffler redesign and custom plastic parts ,will the saw run for over 30 seconds at a time before the piston swells up as tight as a bulls butt in fly time .

Is this a toy saw or one that will get with the program cutting tank after tank full with no problem ? You see all this has never been addressed .All we've been told is this is the fastest 441 on the planet and about the neatest thing going next to beer in a can .

More,more,pics,flicks ,data .

[tlandrum]

it didnt happen without pics and vids.

[Cut4fun]

Posted in wrong thread 

[441FELLER]

i'll post some vids tomorrow, got home late tonight, i'm cutting furniture tomorrow, i'll make some cookie cuts for ya...haha performance muff bolts 

[Al_Smith]

Another quick question...When talking about chainsaws (or 2-stroke in general), is the compression ratio normally not referenced? I may be way off, but to find compression ratio on a naturally aspirated engine couldn't you take your PSI and divide that by the average atmospheric pressure (approx 14psi)?

Thats where it gets real confusing .At sea level the atmosphere is 14.7 psi .Due to the fact it's a two cycle pretty much throws out 4 cycle thinking .

For example a natural asperated 4 cycle relies on atmospheric pressure to fill the cylinder on intake .On a two cycle because of the compression of the crankcase prior to transfer could be as high as 1.5 atmospheres although it seldom is .

Now given say 20 psi going in ,it's pretty easy to see how even a 7.5 comp ratio saw could generate 150 PSI .  It's all about trapped compression and not all that easy to explain .Remember a two cycle works on differential pressures .

Now once you think about all that imagine a tuned pipe that could stuff  half again that much back in the cylinder if it's done correctly .Becomes rather mind boggling if you think about it .