Thinking about modding a MS 361

[Ax-man]

Just about done with this saw . I put new rings in it , didn't do the full base gasket delete . I went with the manila envelope with a sealer . Squish is about .020 -.025. No air leaks and the compression came up ,not as much as I thought it would but it is better. I got the muffler back together after gutting it and adding a second exhaust port. The solder didn't work even though I thought I did a good job . As soon as that muffle got warm it blew that muffler back into two pieces . I brazed it back together and it holding up very well . Another lesson learned.

The carb seems to be keeping up with all this extra air flow . I got it tuned so it is holding a good idle and a quick acceleration. I did a few cuts with it so far so good but I have to back and do some work on the used bar and sharpen the chain better. I have no idea where that carb is set . It had the limiters on it . I set the limiters to fully open and pulled the limiters out and just left it at that setting and went from there . So far no problems with the carb .

Question?? I didn't change any of timing numbers which is why I didn't go for a full base gasket delete. I figured the manila envelope would be a good middle ground between the base stock gasket removal verses no gasket. I tuned the saw by ear to what I felt was right . I checked the high end with a tach and it was only reading about 12,000 rpm. The stock specs for this saw is 14,000 rpm . I did my test cuts with the high end at 12,000 and seemed to do good . I leaned the saw out to about 13,000 -13,500 and it screams, naturally . That 4 stroke burble is there but sounds just a little too lean to me . I am going to try some cuts with it set the way it is to see what happens.

I guess the question is that since the base gasket has been removed and now only has that thinner manila and sealer to seal the cylinder did the timing numbers change enough to where the saw is best left in the lower rpm range or go for broke at the higher rpm's. You wouldn't think these few thousandths of an inch between different gaskets would make that big of difference but I am a little out of my comfort zone on this one. This is the first saw I have actually altered the ports and did a major surgery on the muffler . Getting it tuned right isn't hard but so far has been different than most of the saws I have worked on. How about switching to a 40 to 1 mix instead of 50 to1.

 

[Yotaismygame]

Those new rings will seat. Usually see compression bump 10-15 psi after a tank of fuel. Sounds like you dropped the jug 5-10 thousandths? 10 will change your timing for sure but not very much. I know base gasket deletes are popular but really it’s a trade off. More compression but less exhaust duration. I’d rather keep the exhaust duration. I would go full gasket delete and raise the exhaust back up.

 

[Ax-man]

Thanks, your right about dropping the jug 10 thou. I am going to give this saw a run against my good stock 361 , the Frankenstein 361 and this project ported 361 and see what happens. The thought of tearing the saw back apart and going back to the degree wheel doesn't excite me at the moment. LOL

Oh, I got ahold of some 1/8 th.in. mandrels for that Dremel and polished that exhaust port . That made quick work of that little task . I had some around but I don't what happen to those little things and had to get new ones. I am becoming the Dremel king with all this port altering and muffler grinding LOL

 

[huskihl]

I’d do the gasket delete and leave the exhaust down. Widen the exhaust before you raise it. No sense giving up compression and torque for rpm

 

[cuinrearview]

This exhaust wasn't wide, but it was when I was done with it.

 

[Ax-man]

Looks good. I widen my cylinder also . I didn't go quite that far mainly because this is first go round at widening ports. I see you did some transfer work also . I left them alone because I wasn't quite certain as to what I was doing and I really don't have the correct tools. Just call me chicken #### I can take it. LOL

I couldn't resist starting the saw today . Darn thing fired on the second pull from a dead cold start. Two more pulls to clear it's throat and we were running . So I know I am close to where I need to be on the idle and low jet. Any other 361 I have takes a minimum of at least six pulls before they start running. I had other things to do today but tomorrow I'll try and get that bar dressed and squared and sharpen that chain . Hopefully it won't rain too much and I can get down to our little woods to try it out on some actual wood.

 

[Ax-man]

Finally got a chance to do some real cutting with my modded or should say partially modded 361. I am happy with it except for a few little bugs that don't have anything to do with it's running . I ran this saw against my stock saw and to me it is faster . It by far is the easiest 361 to get started with that muffler mod.

I have been toying with the idea of making a video and posting it upstairs for comments to see if I did actually make a saw faster or just a louder noise maker. Would any of you guys be interested in seeing this if I can get the job done . I don't know if we need another saw or not because after awhile they all look pretty much the same .

I posted a pic awhile back of those two 361 cylinders . One has a hole or port in the intake and the other didn't. I asked what it was for . I think I found out what it is for . It is kind of a safeguard against fuel puddling behind the intake boot if my information is correct.