MS400 Cylinder Thread

[drf256]

I wanted to start a thread on the new MS400 model’s cylinder in order to get some opinions on it and shed some light on its nuisances.

I have personally only wood’s ported one of the model. The design is quite impressive and similar to the 261/462 design as well as other newer Stihl strato port models.

What’s surprising is that the European cylinders appear to have a lower exhaust roof. That gives one more leeway to experiment with timing numbers.

I’d like anyone/everyone to add in their findings regarding the model’s cylinder.

The postings may seem haphazard, as they have been discussed with multiple different builders over the past year.

@Mastermind
@Canadian farm boy
@huskihl
@Stump Shot
@jurchybald

 

[drf256]

The US/CN exhaust roof comes in at .910/23.2mm from the stock squish band.

The EU jug was measured at .925/23.5mm which gives a stock roof of 103*.

Both myself and @Canadian farm boy got around 99* stock and 102 with .040 removed from the base.

@jurchybald is at 107* after .040 off base.

These numbers were measured with a ring and pick, so they are accurate. It’s the method I have personally found to be the most accurate when comparing between different builders.

I believe the degree’s to be more sensitive and accurate than the physical measures.

 

[drf256]

This is the jug I did. The chamber picture is after .035 was cut from the band. I have to check my notes, but 40-45 was removed from the base. With base gasket installed, I hit a 102* exhaust roof. Squish came in at .017.

 

[drf256]

This is the EU jug with a ring at the exhaust roof. @jurchybald does impressive work, so I do believe in the accuracy of his measures.

 

[drf256]

A few degrees can make a big difference in how a saw runs. @jurchybald prefers the 400 over the 462 for logging. I had a hard time getting the 400 to run as well as a woods ported 462, and that was a version 1 462.

I’m trying to figure out if there are different cylinders for the 400 or not.

At least for me, the 462 is around 5 ounces heavier than the 400 and not much bigger.

 

[jurchybald]

Yes here in eu stock exhaust port is at 103 and once I drop the cylinder it's at 106. If I leave it like that 400 becomes one bad mf**er

 

[farminkarman]

Doc, on the 400 I did (only have done one), I cut 0.045” from the band and the exhaust was in the 106-107 range. I raised it back up to 103 on my build because the guy was only going to run a 20” bar.

 

[David Young]

Doc I notice the date stamp on yours is from sept of 2020. and jurchybald has a date of 2.5yrs later. maybe a change in production? are the other numbers the same? Is the combustion chamber the same? A revision was done to the ms 201 where the piston and cylinder are different.
I have never run the 400 yet the 462 was impressive. think they are really on to something.

 

[huskihl]

The ones I have had end up at 105 after lathe work. My longer bar build is at 104 and my short bar build is at 100

 

[srcarr52]

The US/CN exhaust roof comes in at .910/23.2mm from the stock squish band.

The EU jug was measured at .925/23.5mm which gives a stock roof of 103*.

Both myself and @Canadian farm boy got around 99* stock and 102 with .040 removed from the base.

@jurchybald is at 107* after .040 off base.

These numbers were measured with a ring and pick, so they are accurate. It’s the method I have personally found to be the most accurate when comparing between different builders.

I believe the degree’s to be more sensitive and accurate than the physical measures.

I've seen more than 0.015" difference in transfer height side to side on a Stihl cylinder. I'd say 0.015" on the ex port height is probably on either end of their tolerance.

 

[srcarr52]

The US/CN exhaust roof comes in at .910/23.2mm from the stock squish band.

The EU jug was measured at .925/23.5mm which gives a stock roof of 103*.

Both myself and @Canadian farm boy got around 99* stock and 102 with .040 removed from the base.

@jurchybald is at 107* after .040 off base.

These numbers were measured with a ring and pick, so they are accurate. It’s the method I have personally found to be the most accurate when comparing between different builders.

I believe the degree’s to be more sensitive and accurate than the physical measures.

0.015" isn't 4° difference in ex port opening. I'd be suspect of the 103° number as it doesn't concur with your findings of 3° difference with a drop of 0.040".

 

[farminkarman]

The ones I have had end up at 105 after lathe work. My longer bar build is at 104 and my short bar build is at 100

After running the one I built at 103ex, I wondered what it would run like closer to 100.... I might have to try that if I ever get the chance to do another one.