MS361 Big Bore Kit Review

[24d]

Does altitude effect mostly horse power or tork and are saws modded differently to compensate for it?

Later,

 

[blsnelling]

My stock 361 has 168psi... as at yesterday... maybe 100 tanks though it; every one of them 50:1 Ultra.

EDIT: I was wrong.. it's 178.... see later post...

How in the world can this be Andy? I've never seen a stock Stihl saw have that kind of compression. I'm at about 600 feet elevation here, so it's not altitude. I've got a 064 here that's pulling just shy of 170 and that a first for me. Is it possible they've tightened the combustion chamber on the 361?

 

[timberwolf]

Some of the newer saw designs are running higher compression. Highest I have seen yet is Solo 681 at 182 psi bone stock with base gasket installed.

 

[breymeyerfam]

checked my comp on my 361 last night and it was 180. bought it in 2004

 

[blsnelling]

Here's the gallery with all the pictures in it. If one of the mods can allow me to edit my first or two, I'll repair the links. PICTURES

 

[trimmmed]

Here's the gallery with all the pictures in it. If one of the mods can allow me to edit my first or two, I'll repair the links. PICTURES

I can't change the edit time frame, but I can re- insert your pics if you want. You are talking about the 7900 thread, right? If that works for you, just pm me the approp links and tell me which post to put them in.

 

[Lakeside53]

How in the world can this be Andy? I've never seen a stock Stihl saw have that kind of compression. I'm at about 600 feet elevation here, so it's not altitude. I've got a 064 here that's pulling just shy of 170 and that a first for me. Is it possible they've tightened the combustion chamber on the 361?

I'm at 400, and at work I'm about 140. The 361 is definitely higher than most other Stihl saws I measure, so yes, it's likely by desgn.

 

[Lakeside53]

My 361 stock did not 4-stroke above 14K. In fact, it cut best at 13,500. .

Just another data point. Last night, while tuning I played with the 361 I muffler modded (my usual 16mm mod). It clearly 4 stroked to about 15k. With the stock muffler, I have difficulty hearing them 4-stroke at all (they do.. it's me).

I set it at 14k, but the user will no doubt wind it up... he "like's the sound":monkey:

 

[Tzed250]

Brad, I think you should re-fit the 361BB with the correct base gasket so that apples will be compared to apples...

 

[blsnelling]

Here's the 361BB in the same wood I was testing the little saws in a few days ago. The wood is larger as I have moved up the log. For instance, my 260 cut a 2.15 the other day and cut a 2.50 with the same chain with more work today. I'm really aggrivated though. I have a nearly new MS361 here and ran it with the same bar and chain, and again I screwed up with the camera and didn't get the shot.

Running very rich at 14K, running a round ground chisel chain. Time was 2.8 seconds.
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/yo0WbAdM2oo&hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/yo0WbAdM2oo&hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

Tuned to 15,800, running a square ground chain. Time was 2.5 seconds.
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/QVp1ART2bYc&hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/QVp1ART2bYc&hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

It's as fast as my 260 was today. Remember this saw turns 17K and is ported. So for the 361BB without porting to run with it is pretty good in my books. Time was 2.5 seconds.
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/17nYvXdkqhc&hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/17nYvXdkqhc&hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

 

[Metals406]

Man, you can really hear the difference between the 14k and 15-8k! Sounds healthier the second tune... Was it just right or too lean?

 

[blsnelling]

15,800 was right on the edge. I wouldn't go any leaner. 14K was crazy rich. The stock 361 I have here couldn't be turned down below 14,500 with the caps on it. It was still 4-stroking. I run it at 15K for 2-3 cuts but it didn't have the torque there. I'm still ticked I lost the video. I'm almost tempted to put it back together stock just to get the times. But the piston is off, the rings off the piston, the decomp out.... Too much work.

 

[Metals406]

Maybe right at 15k is money then?

Thanks again, for taking the time to document this Brad.

 

[landyboy]

Going back to the out of round piston issue; i thought all pistons were machined this way as when hot the piston would become round. Pistons will heat up unevenly because they dont have a uniforn cross section and will therefore not expand at the same rate throughout its circumference.
Most two strokes require a warm up period to allow for expansion otherwise failure can result.

Cheers Andy.

 

[Tzed250]

Going back to the out of round piston issue; i thought all pistons were machined this way as when hot the piston would become round. Pistons will heat up unevenly because they dont have a uniforn cross section and will therefore not expand at the same rate throughout its circumference.
Most two strokes require a warm up period to allow for expansion otherwise failure can result.

Cheers Andy.

It isn't the piston that is out of round...

 

[landyboy]

It isn't the piston that is out of round...

Didnt say it was. posts 23,26,28,29,48, mentioned out of round pistons so i thought i would submit some boring information just to confuse things.

 

[Lakeside53]

The bore is out of round...

 

[PistonBroke]

Great post Brad!!!!

Thanks for taking the time to keep us posted.