It's 2:00 AM and I just went out to the garage and checked the compression on my 362. lol
Anyway it's 150 dead.
Anyway it's 150 dead.
Inside the MS362
- Thread starter blsnelling
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tdi-rick
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Do you mean the ring pins on the piston ??
Most/all two strokes have to have them, otherwise the the rings would rotate and the ends would snag in a port.
tdi-rick
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Naa,the second throttle is to introduce the straight air (no mix) that is introduced in front of the charge in the transfers to help purge the exhaust and stop fresh charge flowing clean out.
BlueRidgeMark
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rms61moparman
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Is it just me or is there an excessive amount of carbon buildup on top of the piston for a practically new saw???
I would think this saw, running at those settings over a long period of time would have been a candidate for serious carbon scoring.
and
Do you reckon those port castings were left that rough on purpose attempting to improve atomization???
Mike
I would think this saw, running at those settings over a long period of time would have been a candidate for serious carbon scoring.
and
Do you reckon those port castings were left that rough on purpose attempting to improve atomization???
Mike
Terry Syd
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Stratos
Brad, I've tried three times to load your pictures, but my useless computer system won't let me look at all the pictures. I note that someone mentioned a cutaway in the top of the piston. On my 450 Husky that cutaway also has a hole through the piston. I kept wondering about it and I think I know what that cutaway and hole is for on the 450.
The temperature gradients over the piston skirt are likely fairly radical with the strato function blowing across the sides of the skirt. The piston doesn't have to conduct the heat from the skirt through the cylinder and to the cooling air outside the cylinder - it's being cooled directly.
The cutaway on mine is open to the strato port for a short period and allows fresh air to flow to the front of the piston and inside to the hot area at the front and top of the piston. I believe this was done to give the piston a more uniform expansion (it also allows a cooler running piston).
You may want to compute the strato duration. On the 450 the strato port is open before the intake port. The intake has a duration of 144 and the strato port is something like 150. (I forget what it was, but it is longer). That is an interesting twist to my strato in that at idle the intake timing is reduced, but as you open the throttle and the revs build, you get to a point where the throttle starts opening the strato butterfly and the total intake port timing gains duration. It's kind of like a variable timing camshaft (there is also the further analogy to the secondaries on a carburetor with the strato butterfly opening).
Something else to consider, since you dropped the jug, you have also extended the strato timing, something you may want to factor in if you are thinking about extending the intake timing.
If you could post some further pictures of the piston and the transfer ports I'd appreciate it. I'm definitely looking forward to what you come up with on this strato mod.
Edit: the pictures finally loaded. It looks like the Stihl design is very different to the design of the Husky 450. Conceptually it is the same, but entirely different approaches to implement it.
Brad, I've tried three times to load your pictures, but my useless computer system won't let me look at all the pictures. I note that someone mentioned a cutaway in the top of the piston. On my 450 Husky that cutaway also has a hole through the piston. I kept wondering about it and I think I know what that cutaway and hole is for on the 450.
The temperature gradients over the piston skirt are likely fairly radical with the strato function blowing across the sides of the skirt. The piston doesn't have to conduct the heat from the skirt through the cylinder and to the cooling air outside the cylinder - it's being cooled directly.
The cutaway on mine is open to the strato port for a short period and allows fresh air to flow to the front of the piston and inside to the hot area at the front and top of the piston. I believe this was done to give the piston a more uniform expansion (it also allows a cooler running piston).
You may want to compute the strato duration. On the 450 the strato port is open before the intake port. The intake has a duration of 144 and the strato port is something like 150. (I forget what it was, but it is longer). That is an interesting twist to my strato in that at idle the intake timing is reduced, but as you open the throttle and the revs build, you get to a point where the throttle starts opening the strato butterfly and the total intake port timing gains duration. It's kind of like a variable timing camshaft (there is also the further analogy to the secondaries on a carburetor with the strato butterfly opening).
Something else to consider, since you dropped the jug, you have also extended the strato timing, something you may want to factor in if you are thinking about extending the intake timing.
If you could post some further pictures of the piston and the transfer ports I'd appreciate it. I'm definitely looking forward to what you come up with on this strato mod.
Edit: the pictures finally loaded. It looks like the Stihl design is very different to the design of the Husky 450. Conceptually it is the same, but entirely different approaches to implement it.
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demographic
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I don't know saws but every two stroke engine I have seen apart had ring stops to stop them from rotating and snagging like you said.
Four strokes don't have lots of holes in the bore so that's not an issue.
Great thread, its interesting to see the way those stratos are ported.
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alderman
Addicted to ArboristSite
Brad:
Nice tutorial.
I'm impressed and I don't even know what I'm looking at or what the he** you're talking about most of the time.
Did you get to run that saw before you started the teardown?
Nice tutorial.
I'm impressed and I don't even know what I'm looking at or what the he** you're talking about most of the time.
Did you get to run that saw before you started the teardown?
gink595
Addicted to ArboristSite
No. It's part of the strato design. It makes the saw cleaner burning and more efficient.
Most all saws have them.
I think the Schrader valve was loose in my hose. Compression was down about 25 PSI on my 681 too, and there's nothing wrong with it.It's 2:00 AM and I just went out to the garage and checked the compression on my 362. lol
I think it's very excessive. I'm assuming the saw was running WAY rich. I have no idea what oil was used. It was green though. I'm assuming it was Stihl oil.
Yes, it's the impulse passage. No hose to go bad on this model.What is the little hole at the bottom of the cylinder for...Impulse line
parrisw
Tree Freak
opcorn:
Erick
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So Brad, what's the approach gonna be to this build??? Gotta plan yet?
mtngun
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Thank you much for the pics, Brad.
I sat staring at this thing until after 1AM this morning, lol.
Terry Syd
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Zen
"I sat staring at this thing until after 1AM this morning, lol."
I know what you're talking about, I went through a number of permutations of how my strato worked. Each time I picked up the jug I found another "now why did they do this?"
If we could get some SAE papers on the designs it might save a lot of Zen time.
"I sat staring at this thing until after 1AM this morning, lol."
I know what you're talking about, I went through a number of permutations of how my strato worked. Each time I picked up the jug I found another "now why did they do this?"
If we could get some SAE papers on the designs it might save a lot of Zen time.
stihlboy
Guess who's back
this will be the first 362 ported as far as we all know!!! don't screw it up! lol just kidding brad you do good work...........on a side note wanna port a 5105?
gink595
Addicted to ArboristSite
So when you start a port job is there a precedure you normally do... Measurements, timing numbers... What is the process you have when you start a woods port? What makes this one that much differnt? I do understand it is a different design than what you have done but is the idea the same?
huskystihl
Addicted to ArboristSite
Brad, regarding low compression numbers........is it possible that the decompression valve is leaky? I had that same trouble on my 361 and bought the stihl plug for it and the compression came way up.
Waylan
Waylan
parrisw
Tree Freak
Ya just start grinding until it looks good, then call it done!!
