Thinking about modding a MS 361

[Ax-man]

Hello, I normally don't come to this section of the forum except to read and learn . This is my first post in this section of the forum and wondering if I am in the right spot for newbie type questions to do some mods on a MS 361 to get a little more grunt out of the saw .

I got a wild hair up my arse to bring back a MS 361 that had been sitting under my bench . I got some parts saws and got that saw running . Now I am sure I can get a second 361 saw running which is the one I want to hop up a little just to see if there would be a big difference between a stock 361 and one that has had some work done to the cylinder and muffler.

I am not new to this porting and have done a little in the past along with muffler mods. I do have some of the basic tools but it has been a long time since I played with these tools and now that I am retired have some time to do it and may need to post up some pics and questions on what I think I might be doing to this cylinder and probably do a muffler mod also.

Am I in the right place or should I move up to the other forum ??? That one seems to be more for the racing crowd which is beyond my skills.

Thanks

 

[Yotaismygame]

Right place. Not many people view this section though.

 

[Ax-man]

I'll give it a try when the time comes. Seems to be a different crowd here than the regular chainsaw forum.

 

[Yotaismygame]

It is, just not many of us. If you need any help or advice i'll try my best. If you want some machine work done to bump compression send it my way. I don't charge much at all for just machine work.

 

[Ketchup]

Both places will get you the most info. The other forum isn’t just race stuff. Dr Al (MOFO) has some fantastic write-ups about 360/361.

 

[cuinrearview]

I'm working on a 361 right now and I see a lot of easy potential in them. I believe just opening up the muffler would make a huge difference. That thing is sad. If you can open it up and get rid of all of the baffling and add an extra outlet I bet you'll think you have a ported saw. Just a second outlet would help though. The exhaust flange match to the gasket and/or muffler is really poor. To me the intake and exhaust ports look small for a 60cc saw, but if you go grinding be aware of the unconventional bottom ring pin location. I'm not sure on squish yet but optimizing that is always free hp. I'm not sure how these like a timing advance but a quick skim through the aforementioned Doc Al threads should yield that info. Good luck and have fun!

 

[Ax-man]

I'm also putting the putting the finishing touches on a 361 I just got running and for a used stock saw and used parts to make run it came out good with the few test cuts I did today. I hear what your saying about the muffler . I am a long way from getting 361 # 2 that I plan to mod running but I am also thinking the same way you are about making a second outlet and muffler exhaust mods.

I never measured a squish band till I ran into this #1 361 . I only did it because it was so hard to pull over and wondered what the heck was going on inside that cylinder. Before I took the engine apart and decarbonized it I came up .027 to .030 on the stock squish with base gasket. Like I said this was the first time I have done this and their is a trick to it and where to read the caliper. I didn't check it after I got the saw running but that through cleaning and reworking the cylinder made a world of difference in pulling that engine over and ended up with 150 lbs. compression which doesn't mean much to me because that is average.

Now that I have been into this engine it seems to have a short stroke . The 361 is kind of a high revving saw . My Stihl sheets put a 361 at 14 thou. at WOT. I don't really know if playing around with the timing on the exhaust /intake port timing is the right thing to do . I am kind of leaning toward widening the ports on the side a little if there is room and doing something in the area of the lower transfers . That 361 cylinder is kind of like the pics I see of Husky cylinders . If my nomenclature is right it is a quad closed port cylinder which I am not all that familiar with. These are the questions I am going to be asking along with some pics.

Before I get into this saw I have to make a derail and think up something better to hook up the degree wheel I have . Another quickie project I have in mind is one of those chainsaw work stands I have seen on the net . I don't need it but I have the stuff around here and with a trip to the hardware store I can then play like the big boys do .

 

[Ketchup]

How’s about some cylinder and muffler pics?

Closed quad ports are good. EPA mufflers are a PITA.

You definitely want a wheel on it and some stock numbers as a baseline.

Do you have access to a lathe and right angle grinder? A small TIG or oxy welder is also handy.

 

[Yotaismygame]

You can get away with a dremel with pencil attachment, some double cut burrs off amazon, split mandrel off amazon, and sandpaper. Could simply widen, polish, and advance the timing for starters. From there some machine work would be in order. If you just wanted to go the pop up route I could cut the base and piston for a few bucks.

 

[Ax-man]

Appreciate the offer to do some machine work but I just don't want to get that involved mainly because the saw isn't worth it. Thanks for asking to help me out.

I haven't given up on this little project. I just haven't had time to work on saws these last few days .

 

[Ax-man]

I did find a little time today to start playing with this 361. I have to refine my degree wheel method because I had numbers all over the place that I knew were wrong . Mostly either the wheel itself or the way I have it attached to the saw was moving.

Squish seems or close to .030 with base gasket. TDC to when the piston moves down to open exhaust port seems to be about 100 degrees . Transfers open at about 120. If those numbers are correct this saw has a blowdown of 20 degrees correct ?? I have read that is a good number. I don't have the intake number because the cylinder is still on the saw with the intake boot . When I get that apart I'll know more and should have my degree wheel set-up better to get better accuracy.

The transfers are very hard to see when they actually open . That 120 number I came up puts the top of the piston almost exactly about half way down in the exhaust port before it goes to bottom dead center . Did I do this correctly ?? To me this makes sense when the transfers should open even though you can't really see what is goin on inside the cylinder . If I am doing this right is it safe to assume that this is the same for most saws or is it just this 361.

I also peeked inside muffler of my other 361 I have to see what mods I could do to this saw . I was surprised to see a cone shaped baffle inside the muffler instead of the usual rectangle type baffle found on most Stihl saws . I don't know if there is an advantage to this design or not but it seems like Stihl made some type of tuned muffler for this saw but kept it contained inside the muffler itself. The only way to either get rid of it or enlarge the holes in the baffles is to cut the darn thing open which is something I would rather avoid . It is hard to tell how big the stock outlet is but a second outlet seems to be the way to go but be on the conservative side for the second outlet.

 

[Yotaismygame]

Blow down will vary with each saw. No clue if 20 suites that saw. Some saws 20 is good and some it’s not. Sounds like you measured correctly. A flashlight and the right angle will show the transfers. Sometimes looking through the decomp hole helps if available.

 

[Jed1124]

https://www.arboristsite.com/community/threads/lakeside53s-361-muffler-mod-w-photos.33528/

A classic old school AS thread.

 

[Jed1124]

https://www.arboristsite.com/community/threads/lakeside53s-361-muffler-mod-w-photos.33528/

A classic old school AS thread.

Unfortunately all the pics are gone but still a lot of good info.

 

[Ketchup]

100 exhaust, 120 Transfer, 80 intake is the right ballpark. Slight variation makes a big difference though. Every model of saw is different, and often there are differences in cylinders on the same model. You will want to be reasonably confident in your port numbers before you start grinding, so it’s worth repeating the process several times to be certain.

Truth be told, almost no saw is going to see a resale value improvement that will justify how much work you put into a full port job. The value gained is mostly in personal enjoyment of the saw. The process can be satisfying in its own right. It won’t turn a $325 ms361 into a $900 saw, but it’s still worth doing a good job and trying to get the machine closer to its full potential. I personally get even more enjoyment out of improving inexpensive saws. Low investment, high reward.

I understand not wanting to dive straight into the deep end. It can be expensive. I started with saws that were very low financial investment, but I poured hours into them.

Try the “Farmer Jones” approach. It is very affordable and can make a surprisingly strong saw. It saves you a lot of guessing at timing numbers. It also doesn’t preclude later porting improvements.

Just open up the muffler (80% of exhaust port outlet is a safe guideline), set a tight squish (.018-.022”) and port for good flow. Widen (65% of bore is a general max width, if piston skirts allow) but don’t raise or lower ports, smooth all rough and uneven edges, match ports to intake and muffler and encourage smooth flow into the transfer lowers. A slight ignition advance may also help. No machining, expensive tools, or major risk involved. Just hours with a Dremel.

 

[Yotaismygame]

Agreed. I would lower the intake port a touch though.

 

[Ax-man]

Thanks for the replies. I haven't given up on this and have some more questions. I have been doing more reading and vid watching than I have been working on the saw.

The first one is timing . I have never advanced timing on a saw on purpose to make it fire quicker . I have worked on saws that jumped timing for one reason or another and too much advanced timing makes them hard to pull over which is why I never tried to advance timing on saw. I am going to get a little brave on this one and play with key in the flywheel.

Since I had the wheel set-up and decided to see if I could determine where this 361 fires . The best I can tell is this 361 fires at about 20 degrees before TDC. Right or wrong ??? Doesn't seem quite right to me . It should be closer to TDC but this is also a first for me to see what the timing is on a saw with the degree wheel.

I have played with the degree wheel enough to tell that I myself can't really get anymore out of the engine by altering the port numbers. The only thing I haven't checked is how much the ports can be widened out in relationship to the piston. If I do anything really major it will be more in the area of the exhaust and muffler.

What is going on with these two intake ports ??? The jugs are from two different 361's and they are both OEM Stihl. What is that small hole in the righthand jug for?? Is it some kind of boost port of sorts to aid in the air flow. I seen this in the other 361 I got running but I honestly have never seen that small hole in other Stihl cylinders or at least that I remember anyway.

Last question for now. Is there any gains to be made in the area of the lower transfers other than maybe cleaning up the imperfections inside the transfer to help airflow or lowering it a little bit or should this area be left alone as it might effect the new charge making it " lazy" so to speak . This is just a term I picked up on. Don't really know how else to say it. I took a pic of the lower transfers to show the area I am talking about.

 

[Ax-man]

Here are the pics for previous post . Every time I post pics they end up in the wrong place . So I am going to do it this way.

 

[Ax-man]

I finally did it after doing some reading and watching some vids on U tube. This saw is a trial run at doing some actual porting to see what works best for me and what tools I have to do it with. I am not using my better saw parts for this one. My basic goal is to see if the saw will run . If it works I'll give it another try and refine what I have already done with the better parts I am saving.

How does this look other than polishing that exhaust port ??? Go easy on me this is my first actual attempt at actually widening an exhaust port at the cylinder wall. I even got brave and widened the intake as much as I felt comfortable . I didn't do anything to the transfers because I just don't have the tools and I really don't know what needs to be done.

I have to round up a muffler so I can match it to that exhaust port for a muffler mod. I am going to see how things work out with the stock muffler I have .

I could go on and on about this project but the one thing that became apparent to me was that you need really good light to do this type of work on a cylinder . Also I only had a Dremel tool with a flex shaft and it only had two settings, high and low, that wasn't going to work to good either . I bought a used variable speed Dremel from another saw guy and that made a big difference for control and I was able to do all the work with it. Another good thing that is coming out of this project is the homemade saw vice I made . Wasn't sure I really needed to go that extreme but glad I did . It frees up bench space and makes things easier to do especially when it comes time to put the saw back together. I'd post a pic but I am sure most of you guys have one.

Here is a pic , feel free to comment god or bad . I am just a newbie at this but doing this is definitely more challenging than the usual run of the mill saw repairs. I have never paid so much detail to a saw engine along with all the measuring that goes into doing this.

 

[Ketchup]

Cool! Looks just fine from here. With your first port job don’t be surprised if you end up assembling and disassembling many times to change things and tweak details. Put it together with a good squish and see how she cuts!