Scored cylinder how bad before replacement?

[JJay03]

I found this in the 020avs im working on would you get a new cylinder or let it ride?
Its a pretty good mark my nails catches on the piston and cylinder mark. Im guessing it was from carbon cause it was pretty heavy.

 

[fatjoe]

Let it ride

Let it ride.Muriatic acid.

 

[JDNicol]

The cylinder looks to have only aluminium transfer on it. You can remove it with muriatic acid (or oven cleaner) and 200-->400 grit sandpaper. Apply the acid to the AL transfer with the a Q-tip and ensure it doesn't get into any of the ports.
As for the piston as long as the intake or exhaust skirts aren't worn i would sand off any of the high spots on the scored area and be good to go. Do you know what the compression was before you took the top end off? You might want to re-ring it while you got it torn down.

 

[nmurph]

new piston and clean the cylinder.

 

[JJay03]

The cylinder looks to have only aluminium transfer on it. You can remove it with muriatic acid (or oven cleaner) and 200-->400 grit sandpaper. Apply the acid to the AL transfer with the a Q-tip and ensure it doesn't get into any of the ports.
As for the piston as long as the intake or exhaust skirts aren't worn i would sand off any of the high spots on the scored area and be good to go. Do you know what the compression was before you took the top end off? You might want to re-ring it while you got it torn down.

Compression felt real good but im still waiting on my gauge to come in. I think you might be right about the cylinder it might clean up. WOuld like a new piston if its not too much tho.

 

[JJay03]

new piston and clean the cylinder.

Thanks where is a good place to buy a new oem piston? Does a new piston usually come with rings also?

 

[nmurph]

stihl dealer.

 

[wigglesworth]

Thanks where is a good place to buy a new oem piston? Does a new piston usually come with rings also?

stihl dealer.

 

[Streblerm]

If that is a 40mm piston you have lots of choices for replacement including oem. If it is the 38mm piston then good luck. I haven't found an aftermarket replacement and the oem is NLA according to my dealer. I sure would like to find one.

 

[Streblerm]

The piston I'm running in my AVP was much worse than that. I polished with a little 500 grit sandpaper on a flat surface.

 

[fidiro]

I just replaced a ring on a piston much, much worse than that. It starts everytime just fine and pulls great.

I placed a piece of sandpaper on my glass stove top and lightly sanded away some of the high spots. Cleaned up the cylinder and threw on a Caber ring.

Good luck with yours.

 

[blsnelling]

Clean the cylinder, polish the piston, and run it.

 

[JJay03]

Dealer said if anything maybe new rings but thought it was ok also. Trying to decide how to clean up the cylinder where would I get that acid or should I just sand it with some fine grit.

 

[nmurph]

Lowes/HD or a pool supply store.

 

[roncoinc]

In one minit is how to clean with acid..

<iframe title="YouTube video player" width="480" height="390" src="http://www.youtube.com/embed/Fr_Odf9yO4g" frameborder="0" allowfullscreen></iframe>

 

[JJay03]

Picked up some muriatic acid going to try that later.

 

[Eccentric]

Picked up some muriatic acid going to try that later.

Be careful! Wear gloves, long sleeves, and eye/face protection. The acid fumes can be rough. I like to pour a SMALL amount into a little plastic cup and dip the q-tips in that. Keep the jug closed. Don't splash it. It's not gonna kill you, but it can hurt...

 

[JJay03]

Ok thanks for the word of caution. Maybe ill wear my respirator if the fumes can be that bad.

 

[Battenkiller]

Ok thanks for the word of caution. Maybe ill wear my respirator if the fumes can be that bad.

You need an acid-type cartridge for that. Best bet is to minimize the fumes by transferring a tiny amount into a clean plastic milk cap and closing the bottle again as recommended above.

 

[nmurph]

be careful with the fumes; they will rust anything ferrous in a hurry.