Mastermind Meets The MS661 C-M

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Who's gonna pull apart a 1000 dollar unit to snap pictures of something inside the engine and void the warranty? If you say you would show me a picture
 
I'm sure you would I probably would but I have no pictures and have never had an issue on a large 1000 dollar saw. What issues did you have on the 90cc saws?
 
I'm sure you would I probably would but I have no pictures and have never had an issue on a large 1000 dollar saw. What issues did you have on the 90cc saws?
He was prolly bothered by the lack of stock finger ports. I'd be surprised if you could get a 661 for $1000
 
Oh I know we all pull new saws apart and take a look I should have said a new saw that just scattered. .. The average joe sure isn't he doesn't even know how to sharpen a chain or what a spark plug is. I just put my t540xp back together. Guys who live one here may think it's normal to open up a new saw but in reality it's a very very small percentage of users who may actually do it.
 
I'm sure you would I probably would but I have no pictures and have never had an issue on a large 1000 dollar saw. What issues did you have on the 90cc saws?

Well I pulled apart a couple 660s and 390s cause they just sucked stock.

well one of you experts should make a youtube video showing how to do it. :)

Someone send me one I'll gladly pull it apart and take pictures.
 
In regards to examining a "new" saw, here's a bit of my story.

During the adventure I had with the Poulan pp5020, I came home with and checked the comp on the second saw.
BEFORE any gas and oil of mine touched it.
Strait out of the box, compression was somewhere in the 80's (psi).
I dropped the muffler and grabbed my tripod and a light.
The camera I used has limited manual settings, So you often have to set the focus
with a false target then swing the camera back onto subject...yada yada.
Stuff that I now lack the fine motor control to do freehand and envy the active saw builders/Porters for having that deft hand.

anyhow after finding the 2nd saw in the conditon shown in these pics
I put carried the few hand tools needed to drop the mufler
along with me to return the 2nd saw.
Back at the store I simply pointed out that it would save a lot of time for everyone IF I just looked the next one over before hauling it home
And then we all get to go through this same two hours of calling warranty
call centers and issuing instore credit cards and so on...

The guy nodded in agreement and I unboxed the saw in a corner of the service desk area.
After few mins to unbox, remove the sparkplug and drop the muffler
I shined a penlight into the plug hole and saw more lumpy plating
and some scars.
I reported what I saw to the store staff and said I'd preffer to try the
450 rancher instead.
On a general note, the 450 rancher is up to around 10 or so tanks of fuel now
and seems to be getting stronger (yay).
 

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Since my movie night with big Sis got shifted, I'm here to help derail.
So here's a couple of shots inside that 1st pp5020 You can see the lumps in the cylinder wall.
I figure it was just a sloppy wash job prior to the plating step.

No one even wanted the pp5020 back, so It's sitting here still.
If I find a day that I can throw a few bucks at it I might just do a revival on it.
I mean I did think it was worth buying in the first place, right??Copy of P1050707 crop 1.jpg P1050703 crop 1 marked 1.JPG
 
Port shapes play a huge roll in these engines as well Hu. For instance, on many engines I will not lower the intake by grinding. I like to maintain a high case compression in a work saw, so that transfer velocity is as high as possible. That means that the time between the intake port closing, and the transfer ports opening needs to be kept constant between many models, even though transfer heights vary. Lowering the intake, and raising the transfers can kill some models. The MS461 and the MS661 both appear to be this way. In these saws, I alter the shape of the intake, rather than the height to get the time/area I'm needing.
Thanks for that perspective. I guess the intake must be open just long enough enough to get the full volume of air into the case, but no longer, so that the intake closes sooner and allows the case to be pressurized. It's a balance between having a long enough duration to get the volume in vs. having enough pressure/velocity.

It would seem a reed valve would have a big advantage, as the intake event would not be symmetrical and the case could begin pressurizing as soon as it stopped drawing intake air. But then you'd still have the restriction and finite response time of the reed valve.
 
It's all about finding the sweet spot......I thought I was building some pretty stout saws two years ago, but looking back thru my notes from that time shows me how much better I understand the whole induction process now. The saws I'm doing today are in a whole different league, and when one isn't up the par (like the first attempt on this 661) I know it in the first couple of cuts.
 
It's all about finding the sweet spot......I thought I was building some pretty stout saws two years ago, but looking back thru my notes from that time shows me how much better I understand the whole induction process now. The saws I'm doing today are in a whole different league, and when one isn't up the par (like the first attempt on this 661) I know it in the first couple of cuts.
So are you using that case compression angle as a rule of thumb, or is it more based on experience with a given type of saw/porting design?

The other thing I'm still trying to understand is just why transfer velocity is so important - what the effect is and why it helps with power. It's clear that is where the manufacturers are going, with crank stuffers and reduced volume cases and transfers.
 
It varies with case volume.....at least from what I'm able to learn in my little operation. Also, the venturi size of the carb in relation to displacement can change timing numbers. The best thing I've found to use as a learning tool so far, is to always study the original design. I like to try to understand why the designer (who has far more R&D and computer models to draw from) did things the way they did. Almost always you will see that there is a relationship between case volume, carb size, and displacement playing a role in timing number selection.

Many times, just tweaking the design will net far more usable gains than attempting to reinvent it.
 
so are you actually measuring case volume before you start tweaking timing...the more I try to learn the more I figure out im just as cornfused. maybe I just need to get myself a degree wheel. I know id never be able to do what you do in a million years so id never really try but maybe having the wheel would help me better understand.
 
No, I yet to actually try to measure case volume. Some saws are obviously tighter than others. Some have long transfer tunnels that will make to think that they are smaller than they really are.......this 661 falls into that category.
 
:(
It's all about finding the sweet spot......I thought I was building some pretty stout saws two years ago, but looking back thru my notes from that time shows me how much better I understand the whole induction process now. The saws I'm doing today are in a whole different league, and when one isn't up the par (like the first attempt on this 661) I know it in the first couple of cuts.
Sheeez monkey l'm trying to buy two masterminded saws atm that are 2012 models from duromax. And now you tell us back then they are not as good. I wanna cry now! I thought buying some tidy used MMded saws was going to save me some $$$ and give me the fastest saws on the block. I'm shattered....:(:givebeer::cry::sucks::chainsaw:
 

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