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What's going on with this piston? Husqvarna 272xp

RedFir Down

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I want to get some thoughts on this piston.

I'm assuming someone put these "dimples" on the bottom exhaust side of the piston to help carry more oil to the cylinder?

Is that dark patch crusty blow by?

Would you replace the piston?

The saw blows 150psi and the cylinder looks fine, just a few small dark streaks that will come off with some Scotch Bright.

Thanks.
 

Stevetheboatguy

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Sometimes that was done to help eliminate piston slap. A loose motor is a good motor but too loose is too loose. Was halfway common in the late 60's through 70's in ice oval snowmobile racing. Running a slightly undersized piston in a loose bore had less chance of locking up in a heat race, buttttttttt if it was too loose it would crack the skirt off and explode. The dimples allowed most of the piston to be undersized but provide enough support to keep it square in the bore.


Way before my time but have seen it plenty of times.



Steven
 

kneedeepinsaws

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Sometimes that was done to help eliminate piston slap. A loose motor is a good motor but too loose is too loose. Was halfway common in the late 60's through 70's in ice oval snowmobile racing. Running a slightly undersized piston in a loose bore had less chance of locking up in a heat race, buttttttttt if it was too loose it would crack the skirt off and explode. The dimples allowed most of the piston to be undersized but provide enough support to keep it square in the bore.


Way before my time but have seen it plenty of times.



Steven
So how do the dimples allow support for the skirt?
 

kneedeepinsaws

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That piston is done
Measure the skirt but it looks shot
Meteor makes a fine piston.
Yes they do! Love their products. I have also been impressed with lil red barn as well
If they used a center punch, the point of the punch displaces metal and creates a high spot. Same thing happens with piston knurling. Was more common in the past with 4 stroke engines.

thx for clarification!
 

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Thanks for the info and clarification guys, I apprecaite it!
I will replace the piston. (My local deal game me a few boxes of "old" parts that they no longer inventory and I think I remember seeing a new OEM 272 piston kit in there, I'll look tonight)

For those of you that have opened up these mufflers how did you do it?
This muffler has a baffle in the middle with a small tube going to the outlet.
 

Lightning Performance

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Thanks for the info and clarification guys, I apprecaite it!
I will replace the piston. (My local deal game me a few boxes of "old" parts that they no longer inventory and I think I remember seeing a new OEM 272 piston kit in there, I'll look tonight)

For those of you that have opened up these mufflers how did you do it?
This muffler has a baffle in the middle with a small tube going to the outlet.
Open it behind the baffle or open the can and gut it.

That piston looked drilled to carry extra oil in the lower skirt area. Good trick with crappy oil used. Intake injested fines and ruined that skirt.
Piston kit and replace the bearing if it is covered in carbon or crunchies
 

Czed

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Thanks for the info and clarification guys, I apprecaite it!
I will replace the piston. (My local deal game me a few boxes of "old" parts that they no longer inventory and I think I remember seeing a new OEM 272 piston kit in there, I'll look tonight)

For those of you that have opened up these mufflers how did you do it?
This muffler has a baffle in the middle with a small tube going to the outlet.
Red97 deflector on the clutch side of the muffler.
 

RedFir Down

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Post a pic of the one you have.
Here's a aftermarket one I did
The oem I put one deflector in front of the other
Not much louder at all and they breath great.View attachment 278966
You can see the small tube feeding the outlet. This is an OEM muffler.

20210122_115835.jpg20210122_115901.jpg

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