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Inside the Stihl MS500i - SNELLERIZED Style

blsnelling

blsnelling

Retired Hack
Joined
Nov 8, 2006
Messages
53,691
Location
Franklin, OH
I finally got my grubby hands on one of these bad boys. It showed up yesterday, straight off the boat from Greece. I wasn't feeling well last night, so tonight was the night.












The first two things I noticed was that it started in only 4 pulls and had instant throttle response...brand new, straight out of the box, no fuel ever in it, and cold. It was then time to hit the wood pile. I have very little wood here, so only four cuts were made, basically to make sure it ran right. The cuts in this video are the very first cuts it made, shortly after the very first start. It ran very well with good power and not a single hiccup. It definitely has more power than a new MS462, as it should.






It then went straight to the bench, just like most saws that I port.


These next couple of pics were simply for reference should I need them for reassembly.






Here's your burn pattern after the first 4 cuts.


I used a mandrel to cut the squishband. (Thanks Randy! It's the same one you made for me to cut 066/MS660s several years ago). I took the pic after the first cut so that the shape of the squishband would be more evident. I debated doing a popup on the piston, but chose to go with cutting the squishband since the combustion chamber is kind of odd shaped.


After cutting, I use 120 grit and then 220 grit to smooth and even it up. The sanding will remove any inconsistencies introduced with the cutter. You simply sand until all of the cut surface has been sanded, indicating that there are now no low or high spots.


Here's some of my port layout. I like to mark existing port edges, pin locations, and desired port edges.

The intake was smoothed and the roof slightly reshaped. It was not made larger in any dimension. There's very little room to widen the transfers due to the ring end location.


This saw has very short blowdown, so the transfers were only leveled, not raising the front of the port at all. That's why you see a little of the NiSi lining remaining in the port. I left the primaries opening 2° before the secondaries. This is a technique I have done for several years. It's interesting to see Stihl incorporate that into this saw. By the way, these lines are remarked several times as I check and refine my work.




The exhaust was raised several degrees. This gave me some additional blowdown and made up for dropping the cylinder.

 
blsnelling

blsnelling

Retired Hack
Joined
Nov 8, 2006
Messages
53,691
Location
Franklin, OH


Here's some of the final port work.





























OK, I'm probably going to catch some flack for this ugly grinding, but oh well. It's the inside of the muffler and I'm not sure how you'd make it pretty anyway. I suppose bead blasting would help, but I don't have a sand blaster. Fire away! Lol :)



I pitch my tent in the "Just let it flow" camp. I am not of the opinion that there is any performance tuning to these muffler. I believe it's all for sound and decibel control. I simply want it to exit the saw as fast and easily as possible. I could be wrong, but that's how I do it.












 
blsnelling

blsnelling

Retired Hack
Joined
Nov 8, 2006
Messages
53,691
Location
Franklin, OH
Its like Christmas in May! No dividers in the intake boot or cylinder intake? What did the squish start at and whats it at now? Combustion chamber looks pretty small, everything looks good so far, great pics.
No dividers. It's not a true Stato saw. It only has the long transfer runners. Otherwise, it's just a typical 2-stroke.

Well, funny you should ask. I thought it was .025" stock. However, after taking .030" from the squishband, and cutting the base accordingly, I had to take more off to get my .020" squish. Either the stock squish was more than I thought or I took more out of the squishband than I thought. I'm quite confident that wasn't the case though. I have a nice depth micrometer that I got from a good friends ;) @Stihl 041S
 
blsnelling

blsnelling

Retired Hack
Joined
Nov 8, 2006
Messages
53,691
Location
Franklin, OH
The saw feels amazingly torquey. This wood is just awful, especially if you're trying to time the cuts. It doesn't show what I feel. It will take bar length wood to make this saw shine. All excuses aside, it does run very well. I may go back in and raise the exhaust a couple more degrees to see if I can pick up some more RPMs.

After machine work/Before porting
Exhaust - 108°
Transfers - 122°/124°
Intake - 88°
After Porting

Exhaust - 105° and widened to 60% of bore
Transfers - 122°/124° leveled and widened slightly
Intake - 88° only smooth and the interior roof of the port reshaped

I'm considering taking the exhaust up to 102°. What I'm less sure about is whether to keep the added blowdown, or go back to the short 14°/16° of factory blowdown. One option is to taper the piston crown to get the port timing I want. If the saw likes it, I can replace the piston and grind it into the cylinder.

Thoughts? Opinions?
 
blsnelling

blsnelling

Retired Hack
Joined
Nov 8, 2006
Messages
53,691
Location
Franklin, OH
It seriously liked raising the exhaust. It's now at 102°-102.5°. I didn't touch anything else. This thing seriously came alive. It gained a lot of RPMs and didn't loose a hint of torque! I am very pleased with it at this point. Now to get it out and run it with the two 462s I still have here, along with my 440/460 hybrid, and maybe @LowVolt 's ported 461. Might as well throw the 390XP in there.

 
Andyshine77

Andyshine77

Tree Freak
Joined
Jan 25, 2004
Messages
10,843
Location
Cincinnati, OH
It seriously liked raising the exhaust. It's now at 102°-102.5°. I didn't touch anything else. This thing seriously came alive. It gained a lot of RPMs and didn't loose a hint of torque! I am very pleased with it at this point. Now to get it out and run it with the two 462s I still have here, along with my 440/460 hybrid, and maybe @LowVolt 's ported 461. Might as well throw the 390XP in there.


I know a guy with a ported and stock 7900, might be hard to track him do though.;) Forgot a stock 390 too.

So far the saw sound better each time you do something:rock: Stock the saw sounds pretty lame if you ask me, I'm sure it runs fine, just seems to have slow acceleration stock, or at least that's how it sounds. The 462 on the other hand is real snappy.
 
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