Mastermind
Work Saw Specialist
From strato to non-strato........that just sucks.
I do appreciate your thoughts on this saw Brad.
I do like the 562xp more everyday.
Modding The MS261
- Thread starter Mastermind
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From strato to non-strato........that just sucks.
I do appreciate your thoughts on this saw Brad.
I do like the 562xp more everyday.
Jwalker1911
Addicted to ArboristSite
These threads are so cool you guys put some great information out even for someone with no clue on porting it is amazing to see the skill you guys have
Slamm
Addicted to ArboristSite
The 261 with just advancing the timing and muffler modding is a small beast, I can't imagine that modest/correct porting and leaving the strato's intact couldn't make an improved version of itself, by allowing for good gains, while keeping the strato's fuel efficiency and cleaner burning design intact.
While I have no doubt port work like Brad's makes for a fine speed or cookie cutting saw, I can't see it as being efficient, as an overall production saw. While no doubt that design it filling the cylinder with maximum fuel mix, its also likely dumping a decent amount of mix out the muffler without being burned (= waste).
I have a question about porting the strato ports, what good is it to open the openings in the cylinder if you can't open the "tunnels" themselves, it would seem to lower the air/mix velocity? Just wondering.
My non-porting experienced opinion,
Sam
While I have no doubt port work like Brad's makes for a fine speed or cookie cutting saw, I can't see it as being efficient, as an overall production saw. While no doubt that design it filling the cylinder with maximum fuel mix, its also likely dumping a decent amount of mix out the muffler without being burned (= waste).
I have a question about porting the strato ports, what good is it to open the openings in the cylinder if you can't open the "tunnels" themselves, it would seem to lower the air/mix velocity? Just wondering.
My non-porting experienced opinion,
Sam
Terry Syd
Addicted to ArboristSite
I suspect that some of the problem that Brad ran into was because of the four-port design of the Stihl. The ports come up at a steep angle close to the cylinder and then turn sharply into the cylinder. I saw a picture of a piston crown with carbon and I didn't like the flow patterns at all. It is hard to figure out what is going on - short-circuiting, mixing and whatever.
It appears that by compromising the Stihl strato function that all four ports can then just try and bulk flow the cylinder to make up for the unusual flow patterns.
Chainsaws don't require the larger transfer time/area of high performance two-strokes. Two transfer ports is enough for them to flow. The Husky design is brilliant as it is simplistic, the two ports get that freight train of gases moving horizonal and towards the back of the cylinder before it even gets close to the transfer port.
I also don't like the split carb system. I'm a fan of the dual intake and strato system. By having the carb work separately, the idle and low-speed velocity through the carb is sufficiently high that a much larger carb can be used on the intake. When combined with the later opening strato butterfly, the dual system can carry a much larger area of intake to feed the larger area of the strato design.
I don't know Randy, perhaps you can study the piston crown to try and figure out if my impressions are correct - and if so, what sort of tweeks you can make to help the flow.
It appears that by compromising the Stihl strato function that all four ports can then just try and bulk flow the cylinder to make up for the unusual flow patterns.
Chainsaws don't require the larger transfer time/area of high performance two-strokes. Two transfer ports is enough for them to flow. The Husky design is brilliant as it is simplistic, the two ports get that freight train of gases moving horizonal and towards the back of the cylinder before it even gets close to the transfer port.
I also don't like the split carb system. I'm a fan of the dual intake and strato system. By having the carb work separately, the idle and low-speed velocity through the carb is sufficiently high that a much larger carb can be used on the intake. When combined with the later opening strato butterfly, the dual system can carry a much larger area of intake to feed the larger area of the strato design.
I don't know Randy, perhaps you can study the piston crown to try and figure out if my impressions are correct - and if so, what sort of tweeks you can make to help the flow.
Mastermind
Work Saw Specialist
This saw is for a customer, and my customer has one desire. His words to me were this....."whatever makes the most grunt". I do not like the idea of disabling the strato function in this saw but.........I'm building a saw for grunt.
I applaud Brad for wading in and cutting the hell outta a brand new saw to find out what would work the best to add that grunt. I've studied his work and think I may have a few things to add that will help. We will see.
I agree with Terry and Sam here.
Terry's assessment of Husqvarna's strato design mirrors my own. Simple yet very effective.
Feeding the stratos and the intake through the carb is a bad idea for Stihl IMHO.
Sam's statement about keeping the strato's fuel efficient design is the same way I feel about this. Though I don't think this saw is a good example of what can be done with the strato saw. I also feel that just opening the ports at the bore is a waste of time and could even cause the build to go backward.
Actually, the 261 Brad modded in that thread was still quite efficient after he modded it. He traded it to me and I was able to run several tanks through it.
I was getting right an hour or just a hair shy of an hour cut time on one tank. Unfortunately I had to have emergency surgery about three weeks after I
got it and had to sell it. I wish I still had it. It ran great and had a fine power band. True, it wasn't a strato anymore but it ran clean.
I was getting right an hour or just a hair shy of an hour cut time on one tank. Unfortunately I had to have emergency surgery about three weeks after I
got it and had to sell it. I wish I still had it. It ran great and had a fine power band. True, it wasn't a strato anymore but it ran clean.
Mastermind
Work Saw Specialist
Mastermind
Work Saw Specialist
I dropped the jug .025 to add timing to the intake without changing the relationship or height of the ports in the jug. This method works well for me on many saws. It normally adds 7-8 degrees of duration to the strato and intake ports.
I had to cut about .010 out of the squish band to get the squish at .018. Also notice the notches in the cylinder walls I made to unshroud to front lower transfers. The shape of the piston skirt is higher on the exhaust side so I could open that area up some without the piston going below the wall.
I raised the exhaust a few degrees and widened the port at the bore and the flange. Yeah that will get polished.
This pile is the amount of aluminum that I removed from the intake/strato divider.
I had to cut about .010 out of the squish band to get the squish at .018. Also notice the notches in the cylinder walls I made to unshroud to front lower transfers. The shape of the piston skirt is higher on the exhaust side so I could open that area up some without the piston going below the wall.
I raised the exhaust a few degrees and widened the port at the bore and the flange. Yeah that will get polished.
This pile is the amount of aluminum that I removed from the intake/strato divider.
Mastermind
Work Saw Specialist
Here's one thing I don't like about the MS261. It has that damn cheesy little mini spline and tiny clutch drum bearing.
A shot of the exhaust as I as tearing it down.
I told you that would get polished.....
A shot of the exhaust as I as tearing it down.
I told you that would get polished.....
Mastermind
Work Saw Specialist
I never started the saw before I dug into it Mike. I've ran several others stock and muffler modded so I thought.......why get it dirty?????
The only problem I've had so far is with the choke. After removing the divider it has no stop at fully open.
I'll figure something out though.
Mastermind
Work Saw Specialist
I don't blame you on the getting it dirty. They seem to make good power from what I've seen and other peoples reviews. I might have to come visit when I get home.
Anytime my friend. Give me a heads up and I'll drop us a few trees to buck up.
Bowtie
Gearhead
Subscribed on this thread! :msp_thumbup:
I never started the saw before I dug into it Mike. I've ran several others stock and muffler modded so I thought.......why get it dirty?????
The only problem I've had so far is with the choke. After removing the divider it has no stop at fully open.
I'll figure something out though.
Ahh, the choke deal. I forgot about that. I simply run a tiny screw the plastic to stop the linkage from over traveling. Sorry I don't have a pic.
Bowtie
Gearhead
I was thinking the same thing. Any concern of the screw coming loose or is it snug as a bug in a rug?
I use a tiny wood screw and do not use a drill bit. It holds tight and works great.
Randy, the 261 that I owned and traded to JJ had a Zama C3M carb for a 044 on it
Iron Head
ArboristSite Operative
I have this saw and can't wait to see the progress of your mod.
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