MS180 air filter mod

mad_mat222

mad_mat222

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Jun 25, 2018
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Cairns
Went to service the saw and the filter has leaked again. Round peg into an oval hole never works and over time the filter stops sealing around the intake tube. The more revs = more suction on the filter which pulls it off the intake tube = more dirt bypass ‍‍
14AA82B4-53C8-437F-AAF6-4F7A6D00E5FD.jpegE2300441-85FD-4B3E-8E48-CA160E09FCA9.jpeg

The design is really poor. You can see the dirt bypassing near the flat part of the tube(for the carb impulse). Dirt can be seen on the clean side of the top cover as well
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So this is my fix.

The intake tube OD in the air box is 26mm. Got a bit of pvc tube close enough and a socket that had an OD of 26mm. Heated up the pvc with a butane torch and used the socket as a mandrel and stretch to size. Allow to cool on the socket but keep moving on the socket to keep uniform sizing. I sprayed a little silicon in the socket to help removal.

Placed on intake and mark angle of filter. Start cut on pvc above intake tube. I just used the bench grinder to shape. Deburr. Refit and re check. Find a fairly long split pin. I chose a 3.2mm x 40mm stainless pin. Make sure pvc is pressing filter down firmly but not crushing it (There are several plastic locating tubs underneath filter). I happened to have a 3.3mm drill and drilled a hole through. I located the hole touching the filter so the pin would also help hold it down. insert pin on the short side. This prevents the pin being able to fall out and enter the engine. Using a pin this way, makes it a quick change.

Green pen shows contact area with pvc. A seal is created between pvc and intake tube and filter. Also draws the air away from the leak prone area of the intake tube.
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The only concern I have is that the pin may wear it’s way through the plastic.

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Forgot to take a pic but just need to adjust the front of the mod to give clearance for the sealing lip on the top cover. I heated mine up a bit and made the front of the mod more vertical.
 

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Jasonrkba

Jasonrkba

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I never understood what Stihl seen in this design. There is a lot they could have done differently with these saws that would have made them much better and wouldn't have costed more.
 

J D

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I never understood what Stihl seen in this design. There is a lot they could have done differently with these saws that would have made them much better and wouldn't have costed more.
For homeowner grade equipment the goal for most manufacturers these days is to produce a product that lasts the warranty period & that's about it... Case in point
 
HarleyT

HarleyT

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The dirt seems to be entering here. Is that an aftermarket filter, they fit poorly. And yes, I know dealers that sell the aftermarket ones as oem.dirt.PNG
 
mad_mat222

mad_mat222

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100% genuine. They fit ok when brand spankers when All the edges are square, but over time the edges compress around that intake tube and pass dirt because there is no sealing edge. The filter is literally just resting against that tube. Whoever came up with the idea of sticking a dirty great hole in the middle of an air filter needs to be keel hauled.
 
SawTrash

SawTrash

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Jul 3, 2013
Messages
46
Location
Southern Highlands NSW Australia
The air filtration on the MS180 appears to be the same as on the MS170 and yes, it does work very well but only UNTIL the cover is taken off or the filter is removed.

Once the filter is disturbed it cannot be reused satisfactorily and a new one is required.

Whether the design is good or not depends on which side you are on. From the owner's point of view it's bad, from Stihl's or the dealer's it's good.

My fix is easy, cheap and works well.

Using the original filter as a template cut a slightly larger piece from a vacuum filter bag. Punch a 7/8 inch hole as shown in the pic. Vacuum all the dust and grit off the old filter and replace. Put the newly cut piece
over and work it tightly around the intake spigot. Replace cover carefully. Saw wood.

I have not noticed any diminution in performance - and there's no way to adjust the 170 carb anyway.IMG_20210618_112409.jpgIMG_20210618_113237.jpg
 

J D

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Apr 19, 2020
Messages
728
Location
NZ
I have not noticed any diminution in performance - and there's no way to adjust the 170 carb anyway.
Sounds like a good fix. I have a couple of older saws I use the trimmed vacuum filters on & it has worked well so far.
For the 170/180's I usually either replace the fixed jet in the carb with one of the earlier, slightly bigger ones... Or drill it out by 0.05mm to get them running right
 

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