Porting mistake on stihl 440

Mark513 · May 7, 2024

Hello OPE forum, and thanks for having me! I know the professional saw mechanics know the answer to this one. I have a nice 440 magnum, and after reading and seeing all the porting and performance threads on here decided to try it myself.. well all was goin well until I slid the cylinder back down to check my progress on the exhaust port and to my surprise I could just see the edge of the piston where the wrist pin goes through on the right side..I went too far... ugh! So my question is, is this cylinder trashed??

hacskaroly · May 7, 2024

Mark513 said:
well all was goin well until I slid the cylinder back down to check my progress on the exhaust port and to my surprise I could just see the edge of the piston where the wrist pin goes through on the right side..

Can you post pictures, that will help a lot!

Mark513 · May 7, 2024

No pictures yet, saws at work,but you can slightly see the edge going down on stroke and then it disappears ,then on the way back up the same.. On the straight edge where wrist pin is at. Will get pictures tomorrow.

Canadian farm boy · May 7, 2024

As long as you have a nice arch to the roof of the port and just a sliver of the port edge open you may be able to get away with just a different piston. Maybe a meteor piston or a piston from @Duke Thieroff will have enough skirt width?

Mark513 · May 8, 2024

Here’s a shot from the far left of the exhaust port, the left side seems ok

thompsoncustom · May 9, 2024

Gonna need a wider piston

drf256 · May 9, 2024

Find another jug. Unless you can guarantee that a meteor is wide enough to cover that gap (I do know that the 52mm 046 slugs are wider-not sure on the 50), it’s gonna cost you more in time and effort to make a piston from another saw model work.

You can go to CCC racing and check. Dave had some Wiseco slugs made, and the skirts may be wider than stock. The issue will be the price.

Many times you spend more time and effort trying to fix a mistake than by just starting over. I have a feeling that this is one of those times. We all have a “junk pile”. I am speaking from experience.

50mm oem 044 jugs are plentiful used. A lot of guys hybrid their saws to 52mm and keep the 50mm jugs. I have quite a few here if you are interested in a used oem one.

Mark513 · May 12, 2024

Thanks guys, as you can see the piston is in good shape, and I have new oem rings to put in,so I should probably get one of those used ones from drf256.

Porting mistake on stihl 440

Mark513

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hacskaroly

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Mark513

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Canadian farm boy

“Normal” people scare me.

Mark513

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thompsoncustom

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drf256

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