Home owner MS170 Versus pro saw MS200 contest

[nimblebee]

Hello, I'm located in northeastern Kansas and new to Forestry Forum.  Lots of reading and researching, since going to work as a groundsman for a tree service company.
I realize there's a huge learning curve ahead of me, and so I'm not in any hurry moving up to climbing/bucket work (& NOT interested in supervising a work crew, either! lol :-).
My last job I worked as an outboard motor and boat repairman, so naturally I was inclined to learn all that I could find available about porting and modding work saws, making them useful as possible.
The business owner regularly works on and modifies his equipment, and I was encouraged to learn by purchasing a parts saw and all the necessary ingredients to build my first modded and ported chainsaw.
After trying out all the work saws available at the tree company, and comparing an MS200 to an MS170, I found myself fascinated by the concept that MS200 and MS170 had nearly the same displacement, yet clear power winner was MS200 pro saw.
This started my "curiosity bump" itching (IE: head-scratching lol) and I wanted to find out what the difference was?
Both saws had similar weight & power ratings (170=1.3 kw, 200=1.7 kw), 170 had more plastic than 200, with it's more durable metal shell, but internally, it appeared specs for working bits were about equal as far as wear and tear goes?  
This was a puzzlement to me, and I like for things to make sense and be understandable lol :-)
When I asked tree company business owner what the differences was, it was suggested that I might best learn by purchasing a MS170 parts saw to build, and learn porting and mods as a way of educating myself what differences are and why performance was so much notably better for a ported-modded saw.
BO told me that if my MS 170 didn't equal or beat his stock MS 200,  I would need to change the model designation of my saw to "B.S. 170+"  lol :-D
And that's where I am on my journey: I'm learning, reading everything I can and of course watching tutorial videos.  
I've purchased a parts saw, non-RPM limited coil, an aftermarket tunable carburetor, necessary burrs/stones to do porting work, timing wheel, and reading, reading, reading (!) forum posts by such distinguished performers as Randy "Mastermind" :-)

[mike_belben]

I dont think mastermind posts over here.  Hotrodding saws is a lot more popular on AS but there is a much different culture over here.  @HolmenTree is the resident cookie racer.  

Take care of that MS200.  Theyve skyrocketed in price.  Biggest chainsaw buying mistake i ever made was saving a few bucks on the 192T.. Only new saw i ever bought. 

[ladylake]

 A ms170 is the bottom of the line Stihl.  Steve

[sawguy21]

They are similar displacements but two entirely different saws. The 170 is the entry level homeowner saw and while suited for its intended purpose it is limited. The MS200 is a full on pro saw geared for the tree services and is the industry standard, nobody else came close for light weight, performance and reliability.

[nimblebee]

Take care of that MS200.  Theyve skyrocketed in price.

MS170 is the only homeowner saw on the tree service truck I crew, everything else is pro-grade.
MS170 wound up on bucket truck, after tree service business owner bought saw for his wife, and she rejected it, but not before pasting it with "flowery" stickers!  lol  :-)
Once trialing MS170, B.O.'s wife said she was "through with it" and refused further usage (suppose that's the case, once one's become accustomed to pro saws?).  
We keep her MS170 on our chipper for trimming down oddly-shaped limbs which invariably refuse feeding into chipper.  MS170 does a good job for that  :-)  lol

[nimblebee]

Thought I would post an update on progress with MS170 parts saw. While there're a lot of activities and other priorities I'm working on, with time off work for holidays, I've been able to accomplish some progress on the saw.
I've finished muffler modification, installed non-RPM limited coil, new spark plug, new oil line & fuel line/filter, brand new chain (original chain's soaking in bar oil), installed aftermarket, adjustable-tunable carburetor, new air filter, J-B Welded numerous defects/damage to plastic,  removed and cleaned a ton of dirt, debris, gum-oil-sawdust-mix and plain old "yuck" impacted into saw's every crease and crevice, and on the list goes!   :-)  lol
Without access to a lathe or mill, it's going to be a challenge utilizing out-of-the-box thinking, devising means for reducing squish to 20 to 25 thousanths & providing 40 thousandths worth of squish band in bottom of cylinder "a la Mastermind."
After reading everything I could on forums and watching tutorial videos, believe I'm starting to get a handle on porting transfers, adjusting timing, and various non-intuitive intricacies being put forward by top builders with their posts and supplementing videos.
How long is my first port job going to take to complete? idk. Had to purchase a few more tools needed, which should show up next week.   In the meantime, I'll have a working saw with a muffler mod and tuned carburetor to use.
For me, the fun is in doing something new and different, enjoying learning something interesting that's useful.

[Ianab]

No issues with you "hotting up" a cheap little homeowner saw, it's your saw and your time 

But I look at like Hotting Up a 1600cc Corolla back in the day. A bog standard 90s Corolla made about 110 hp. Sure you could rework it to get more (that's your MS170). But a JDM 4A-GE powered "Corolla" had closer to 170hp from the factory, from the same size non-turbo 1600cc engine (MS200). 

Difference was the internals (and externals for that matter were completely different. The 4A-GE red-lined at about 8,000 rpm (factory), and had ALL the go fast goodies already. There wasn't much more that could be done to hot up the engine, but it was still a completely reliable Toyota engine. 

The "normal" engine hotted up to make 170 hp had a pretty limited life as the internals just weren't up to the extra revs and power. 

But don't those observations put you off  ;D

[nimblebee]

No issues with you "hotting up" ... it's your saw and your time  
...engine hotted up ...limited life as the internals just weren't up to the extra revs and power. ;D

Here's something interesting:
Of the half a dozen or so top builders I'm aware of, I'm finding a lot of mentions in postings noting porting makes their builds run cooler, providing more power, without sacrificing longevity or decreasing reliability ...  
It's just when moving from work saws more into race saws territory, one sees posts where power is increased 40+% with consequent sacrifice of longevity ...  
I really don't maintain interest in race saws, but ported work saws? ...   More power, faster performance, more work accomplished in less time...  What's not to like?  :-)  Yes!  
Ported and modded work saws are reported to be practical for everyday use, which is where I find myself, since working for a tree service company.

[nimblebee]

Who wouldn't want a metal lathe and mill? Plenty of fun projects you could do with that! lol  :-)  Most certainly, modding and porting chainsaw customization's.
For those of us born without a silver spoon in our mouth (IE: born to follow a budget ... was born with nothing and still have most of it!  lol  ;-), if searching sufficiently, one'll encounter other's "poor boy" solutions.
Here's an interesting example by top builder "tree monkey", cutting a squish band by hand (a task which I believe lies in wait ahead, in porting/modding MS170 parts saw):
https://www.youtube.com/watch?v=IauT5TZskqU
At the conclusion of porting's learning curve and fun building, lies a competition between tree service business owner's wife's (try saying that three times fast ) totally stock MS170 and my built-from-parts-saw of a ported and modded MS170, with all the "tricks of the trade" and "bells and whistles" I could provide.
I shouldn't have too much trouble meeting that mark in surpassing stock, but comparing cheap entry-level MS170 homeowner saw with industry-standard commercial grade MS200? idk

I'm guessing from comments received in this thread, that I might as well change model designation of my ported and modded saw from MS170  to "B.S.170+" as suggested by tree service BO in my first post. lol  :-P

We'll have to wait and see! Guessing is good, but there's nothing like trial & proving in real world results  :-p   howsoever, ...not taking any bets! :-)  lol

[lxskllr]

Sounds like an interesting project, and a good saw to practice on. If you totally hosed the whole thing, you're not out much money for the saw, and you have a bunch of new toys tools to try again with your new experience.

[ladylake]

  

   You cant cut squish on a clamshell engine.  Steve

[mike_belben]

On split case saws, jugs with a lip you put the jug on a dowel in a lathe. On a clam the bottom of the jug is the top of a bearing. Cant do it.


I used to use wood dowels with electrical tape to shim for cutting squish with a skirt extension in the way.  Then put a screw through the port into the dowel to cut the base with a right hand insert holder in the lathe.   I also had made a squish cutter for jugs that had that silly lip in the top corner of the head.. 041 comes to mind.  It was a piece of barstock with a slit and pinchbolt that id clamp a carbide insert into and turn it out by hand.




The temps will go down from a muffler mod and fatter tune because there is more mass of fuel and air being moved through the pump per unit time.  That mass absorbs more BTU from the hot metal in the process of getting the mix up to temp for combustion.  Higher rpm means higher CFM through the fanwheel also so there is greater mechanical cooling to the exterior jug fins and muffler body.  



If you cant bump the compression by cutting the base of a jug, just weld a dome on the piston.  I set mine in a tuna can of water and gave a lot of time between layers to keep from getting the skirts out of round. Then shape on a sander and hand file/sand to finish.     You can also epoxy the base cavity to increase the base compression ratio.  Done this on 041, 353 and 61s.   Just beware that a really high compression saw will need a decompressor or itll break the homeowner starter.  Think theyre metric 10x1.0 threads on the decompressors.  Ive put them vertical right next to the plug on jugs with no pad cast in.



When you get that 170 to make a bunch of power the clutch will slip.

[nimblebee]

Posted by lxskllr: Sounds like an interesting project, and a good saw to practice on. If you totally hosed the whole thing, you're not out much money for the saw, and you have a bunch of new toys tools to try again with your new experience.
Answer:

I bought the parts saw for $20 off of fleabay ...  What killed me was shipping     ...   Reminds me of a "Hagar the Horrible" cartoon: Salted Herring Free! ... water to go with that, $5 a drink  >8'@
Posted by Ladylake: You cant cut squish on a clamshell engine.  Steve
Posted by mike_belben: ... On a clam the bottom of the jug is the top of a bearing. Cant do it. ...

Answer:
I'm contemplating "work-arounds" on that one! ...  If you've ever cast a bronze bearing into a windmill gearbox, you'll recognize my thought process: using parts which run against bearing surfaces (or forming a waterglass/sand core), and casting a form-fitting bronze insert ...  Might have to do some home chrome plating for longevity? idk, cross that bridge when I come to it, I suppose?

Posted by mike_belben: "weld a dome on the piston"

Answer:

I really like the notion of forming a dome on top of the piston... That sounds like something that's pretty doable to me, without having to mess with bearing surfaces.     :-)

[nimblebee]

If you cant bump the compression by cutting the base of a jug, just weld a dome on the piston. ... You can also epoxy the base cavity to increase the base compression ratio. ... will need a decompressor ... Ive put them vertical right next to the plug on jugs with no pad cast in. ... When you get that 170 to make a bunch of power the clutch will slip.

Great information there, Mike! Thanks for reply and sharing your knowledge and experience.
Doming piston and epoxy the base cavity sounds like some really good workarounds worth considering  :-)
Good to know best location for installing decompressor.
I'd say Mike, when the 170 puts out enough power that it's clutch start slipping, I've gone as far as I can take it, and it's time to stop!    >8'P

[mike_belben]

You probably wont find much extra space residing inside a clamshell compared to the split crankcase castings.  But youve got two compression ratios in a saw, thats why youll feel two lumps in the rope.  It only counts if you get the mix above the piston. 

[nimblebee]

It only counts if you get the mix above the piston.

There doesn't seem to be many forums discussing improvements to be obtained from clamshell designs ... posts read thus far indicate it's worth while modifying clamshell for increased performance via widening ports in getting more mix "above the piston," as you've noted.
Here's one example of a forum discussion on porting clamshells ... https://opeforum.com/threads/clam-shell-porting.6133/

[donbj]

You probably wont find much extra space residing inside a clamshell compared to the split crankcase castings.  But youve got two compression ratios in a saw, thats why youll feel two lumps in the rope.  It only counts if you get the mix above the piston.

Mike, what do you mean by two compression ratios in reference to the two lumps in the rope? When you said that I realized the rope thing but can't picture what's going on "in there". Never really thought about that.

[nimblebee]

My research on various forums shows clamshell engines sometimes are "somewhat" ported (squishing/porting clamshells being problematic); more often modifications for performance enhancement utilize muffler mods, advancing ignition timing, & aftermarket carburetor re-tuning.
How much performance increase is managed?  YouBoob videos show about a 25% increase using above three simplest methods. 
Utilizing "log cut time test," going from unmodified 12 seconds cut time down to about nine seconds with modified saw, or in other words (if my math is correct lol) about 25% increase.
How much increase could you get with the full porting work? idk.  Have yet to locate YouBoob video showing fully ported clamshell saws tested.
Stock results, 12 seconds: https://youtu.be/lIjOaEMy0WE?t=45Modified results 9 seconds: https://youtu.be/jSCzPxHOfRI?t=20

[mike_belben]

A 2 stroke sucks through the carb and into the block while the piston is rising.  The high vacuum of the pistons syringe like movement will get the motion started and then the high inertia of the fuel/air mass at WOT will continue to ram mixture into the block even as the piston descends which should spit fuel out but does not.  The port floor and skirt length dictate at what crank degree the "intake valve" closes and ends the suction event.  
Once the intake closes... the piston continues to descend, simultaneously compressing the crankcase gasses [the first lump] and then revealing the top of the piston by unblocking the top of the transfer port.  Now the piston becomes a trash compactor of sorts.  It shoves the junk from one chamber to the other.  Anything you can do to get more junk from the block to the jug will make for more cylinder pressure and torque when the plug fires.  
This is why we play with the size, shape, layback angle and timing of transfer ports.  If your block has lots of casting cavities it can fit more mixture, true.  But when the piston is trying to shove mix into the transfer leaving spots to hide reduces the quantity forced up. 
I have milled skirt windows in pistons to get the gas trapped under the pin to move over into the transfer port, with good results.  Remember syringes have flat bottoms. Hydraulic cylinders have flat faces. 4 stroke pistons have flat tops.  So a 2 stroke on the downstroke has a bunch of junk in the way of flow to the transfers
Filling in open corners and pockets with epoxy lowers the volume in the block which increases the compression ratio between block and combustion space.  Remember that combustion pressure is still high in the chamber and waiting to be exhausted.  when the transfer port opens higher pressure from the block helps the charge penetrate into the combustion space faster and more thoroughly.    Torque goes up. 

[mike_belben]

Man i put like 20 spaces into that story.  I dont know why it loses them.

[nimblebee]

Once the intake closes... the piston continues to descend, simultaneously compressing the crankcase gasses ... Anything you can do to get more ... from the block to the jug will make for more cylinder pressure and torque when the plug fires.  

Good information to know Mike! I've never considered modifying crankcase volume for increased power  :-)

This is why we play with the size, shape, layback angle and timing ...when the piston is trying to shove mix into the transfer leaving spots to hide reduces the quantity forced up.  

Satisfying to have your explanation of "why" behind increased power... I will need to look further into layback angle, as at this juncture, can't comprehend it's involvement ...

"leaving spots to hide" sounds familiar to the explanation of crowned pistons, where "leaving places to hide" results in unburned fuel...makes sense from that perspective.
Quote from: mike_belben on Wed Dec 30 2020 08:44:45 GMT-0600 (Central Standard Time)
"I have milled skirt windows in pistons to get the gas trapped under the pin to move over into the transfer port, with good results."

Mike, I have read of this concept before, and still have more learning to go to completely comprehend how and where best to apply this process on MS170 I'm learning on.

Quote from: mike_belben on Wed Dec 30 2020 08:44:45 GMT-0600 (Central Standard Time
Remember that combustion pressure is still high in the chamber and waiting to be exhausted.  when the transfer port opens higher pressure from the block helps the charge penetrate into the combustion space faster and more thoroughly.    Torque goes up.

I have certainly learned a lot through your posts Mike.  Thank you. That's one of the best things about being human: No one has to know everything. We can all learn from each other.  That works great!

Long as one can sort out the liars! lol ;-P ...  One of my favorite sayings: "Those who can, do.  Those who can't do, teach.  Those who can't teach, teach gym classes (Woody Allen).  Those who can't teach, preach. and Those who can't preach, are politicians"    :-D

[donbj]

A 2 stroke sucks through the carb and into the block while the piston is rising.  The high vacuum of the pistons syringe like movement will get the motion started and then the high inertia of the fuel/air mass at WOT will continue to ram mixture into the block even as the piston descends which should spit fuel out but does not.  The port floor and skirt length dictate at what crank degree the "intake valve" closes and ends the suction event.  
Once the intake closes... the piston continues to descend, simultaneously compressing the crankcase gasses [the first lump] and then revealing the top of the piston by unblocking the top of the transfer port.  Now the piston becomes a trash compactor of sorts.  It shoves the junk from one chamber to the other.  Anything you can do to get more junk from the block to the jug will make for more cylinder pressure and torque when the plug fires.  
This is why we play with the size, shape, layback angle and timing of transfer ports.  If your block has lots of casting cavities it can fit more mixture, true.  But when the piston is trying to shove mix into the transfer leaving spots to hide reduces the quantity forced up.
I have milled skirt windows in pistons to get the gas trapped under the pin to move over into the transfer port, with good results.  Remember syringes have flat bottoms. Hydraulic cylinders have flat faces. 4 stroke pistons have flat tops.  So a 2 stroke on the downstroke has a bunch of junk in the way of flow to the transfers
Filling in open corners and pockets with epoxy lowers the volume in the block which increases the compression ratio between block and combustion space.  Remember that combustion pressure is still high in the chamber and waiting to be exhausted.  when the transfer port opens higher pressure from the block helps the charge penetrate into the combustion space faster and more thoroughly.    Torque goes up.

Thanks for that Mike. I appreciate the time you took for that detail! Going to read that a couple more times to get more of it. I guess I should take an old cylinder and piston and note the ports as it travels up and down.
I never really did much wrenching on two stroke, just ran em. Picking up two pickup loads of chain saws I better get with the program! Thanks again.

[mike_belben]

Well, im a pretty good preacher too. 


Make the top of the transfers point the charge at the carb so it:

A. Pushes as much spent gas out the exhaust as possible

B. Doesnt blow fresh fuel right out the exhaust port during overlap. 

[mike_belben]

Youre welcome don.  Take one of the junk saws and cut the jug in half.  Also pull one side of the case and youll have your model.  



Whenever i do a saw i am porting the case and transfers together as one unit for flow quality, no ledges or lips left behind.  I will trade compression for laminar flow any day. 




  If theres anything turbulent and im feeling frisky enough to do all the work, it gets epoxied.  Devcon A2 with full paint removal, dimpling for tooth and usually drilling and pinning in tig filler rods for the epoxy to bond to if its a big chunk.  None has ever come off.  I did it in automotive intake ports and oil pumps for years.  And no i didnt learn it on youtube, i taught myself.  

[nimblebee]

I have milled skirt windows in pistons to get the gas trapped under the pin to move over into the transfer port, with good results.  

Mike, in a video series explaining porting by Scott Kunz, I've located an easy-to-comprehend (for me) explanation concerning removing some piston skirt, so as to create a "window" ... porting video series part 3, squish part 2 - YouTube ...  

This adds to my understanding of your post, about modifying piston and allowing gases passage from underneath piston ...