Stihl 028 AV Super... is it worth fixing?

[SteveoSupremo]

Those horizontal striations you mentioned look suspiciously like the rings being "welded" to the piston.

Yea I think the rings are welded to the piston..... they horizontal striations are on the inside of the cylinder. looks almost like a tool mark from the machining of the cylinder.

Just a thought... could I be not getting a spark??? I should probably check that.

 

[Evanrude]

You've got a melted piston there. The intake side of the cylinder may be alright, your description is hard to follow. Regardless, you need to pull the cylinder and see what the exhaust side looks like. It's hard to tell from the pics if the cylinder is salvageable or not. Piston is definitely toast though.

 

[watsonr]

You've got a melted piston there. The intake side of the cylinder may be alright, your description is hard to follow. Regardless, you need to pull the cylinder and see what the exhaust side looks like. It's hard to tell from the pics if the cylinder is salvageable or not. Piston is definitely toast though.

Yep, time to take it apart, that thing is toast.

 

[Clarkbug]

I agree, time for teardown.

Clean any other dirt/dust/grease off of it and pull the cylinder off to see how bad the damage is on the inside. Post more pics here, and go from there.

 

[SteveoSupremo]

Mods?

so i'f I'm planning on doing this are there any mods that I should consider? mainly I would like to quiet it down, cool it down, prolong life and add power.

Basically I want it all.... ;-)

 

[Clarkbug]

My advice is to go one step at a time. Pull the jug, see how it looks and if you can clean it up. Get a new piston for it, and get that in, then try and figure out what killed it the first time. A muffler mod is probably the place to start, but that makes it louder, not quieter.

As far as more power, there are a number of guys here that you could send it to who would port it and make it a nice working saw.

 

[SteveoSupremo]

The Jug... aka Cylinder

so I was able to pull the cylinder today took about an hour start to finish. not half bad.

looking at it doesn't look like there are any groves mostly looks like there is aluminum transfer around the exhaust. looks like there could have been some aluminum transferred out the exhaust port as well. I do see some pitting near the intake.

here are the pictures. I'll get some extreme closeups tomorrow and post them up.
View attachment 226477
View attachment 226478

The piston is toast! the rings are welded to the piston. so I guess it's a new one. how do I pull the shot one out? i got the sholder rings out but the center did not push out like I was expecting.

Now for a new piston do I go cheep $26 piston? Chainsawr Stihl 028 Super chainsaw piston assembly 46mm ST0025 (Box Z)
or do I spring for the Meteor at $45?
Bailey's - Meteor Piston Assembly for Stihl 028
why should I get the expensive one? will it hold up to more heat? give me more power?

and while I'm at it should I re-build the carb? and new filters?

Thanks for all your help.

 

[watsonr]

Its a better quality piston.... it may last longer, have better heat tolerance and just in general better clearances... Don't cheap out for $20

Cylinder looks like it will clean up easy, watch this video of how http://www.arboristsite.com/chainsaw/130474.htm.

Find out why it burned up or it will do it again no matter what piston you put in it. Pressure testing here http://www.arboristsite.com/chainsaw/42768.htm

get a service manual, watch a couple video of how to rebuild a saw. Rebuild the carb, new fuel line and filter.

 

[SteveoSupremo]

I think the piston burnt up because I ran fuel that had a Oil to fuel ratio that wasn't good for this saw. The manual states that it requires a 50/1 if your using Stihl oil or a 25/1 if using another brand oil. I ran some other mix that was somewhere between 50/1 to 100/1 through it. that's my guess.

How do I pull the piston pin? I have already removed the snap rings but the piston pin isn't pushing out easily.

thanks
Steve

 

[Clarkbug]

Sorry to hear that you essentially straight gassed your saw.

Try the acid to see if the cylinder will clean up. Northwood saw (another site sponsor) also has the meteor pistons if you are looking around.

I used a small socket to push the wrist pin out. Just take your time with it, and it should come out on its own, perhaps with very minor persuasion.

 

[SteveoSupremo]

Sorry to hear that you essentially straight gassed your saw.

Try the acid to see if the cylinder will clean up. Northwood saw (another site sponsor) also has the meteor pistons if you are looking around.

I used a small socket to push the wrist pin out. Just take your time with it, and it should come out on its own, perhaps with very minor persuasion.

I'll give the socket idea a shot. I did just find Northwood saw I'm planning on purchasing everything from them after I make sure I can get the cylinder cleaned up! Northwood saw has the best prices I could find.

thanks

 

[RiverRat2]

The cylinder does look like it should clean up.. just direct the muratic acid to the transferd aluminum,,, as long as it keeps bubbling there is aluminum there,,, when it quits bubbling you have it clean, then move to the next spot... once a qtip gets loaded ditch it for a fresh one... and rinse the bore with warm water as you go

yes Northwoods has the best pricing,,, Meteor piston all the way,, Italian made,,, IMO way beter than the Chicom,, Cr@pola!!!

 

[SteveoSupremo]

Acid Done!

ok so I did the q-tip acid wash here is what I came up with.
View attachment 226839
I think I still need to hit it with sandpaper 600 grit wet dry?

There is some pitting where the streaks started will that be ok? what can be tolerated?

thanks
steve

 

[RiverRat2]

The streaks are common with a piston crash,,, I dont see anything to worry about, yeah you can try the sand paper but IMO 400 would be better than 600 with some marvel mystery oil for lube,, take some more photos when you think you have it clean,, I would keep hitting the high spots with fresh acid,,, on clean q-tips,,, if it is still bubbling it still has aluminum transfer you have to get it clean,,

 

[SkippyKtm]

ok so I did the q-tip acid wash here is what I came up with.
View attachment 226839
I think I still need to hit it with sandpaper 600 grit wet dry?

There is some pitting where the streaks started will that be ok? what can be tolerated?

thanks
steve

Your photos indicate that you have a ways to go. Hit it with another round of Muriatic acid then sand it with some 600 grit silicon carbide wet/dry. When you're done it should feel smooth.

 

[SteveoSupremo]

Cylinder all done?

Well here is a picture after I have sanded and and ran a couple more acid baths. I can't feel any scratches with my finger or my nail.

View attachment 227193

the brown is a reflection from something.

I got the wrist pin pulled it was in kind-of tough but I got it. now to figure out the carb, get new parts, and put it together.

so I think the gas I put in was 50/1 of non stihl oil is this what I would have expected? or is there a leak in the manifold or carb?

 

[Clarkbug]

That looks a lot better than the first shot you had, so definite progress.

As far as your mix, how fresh was it? Any idea what oil? I would say that you should dump whatever it was, go buy some quality 93 octane stuff (if you can get non-ethanol, thats a plus), and get a high quality synthetic mix. For starters it wouldnt hurt to drop my your local dealer, grab some Stihl Ultra in a size that matches what your gas can is, and use that for a bit. Your exhaust port looks like there is a fair amount of carbon in it, it wouldnt hurt to gently scrape some of that out while you have the jug off of the saw.

You may have a leak somewhere in it, but we cant tell you that you do from here. When you said it was running lean, you turned up the gas mix to compensate, so there is probably a leak somewhere. Look closely at the rubber boot that connects the carb to the jug, and also your impulse line. Its a good idea to replace the impulse line and fuel line while you have it torn this far down anyway. Good excuse to go see your local dealer and pick up that oil. Then once its all back together you can pressure vac/test things to see if you have any bigger problems.

Good work so far, the folks here will help bring you the rest of the way in. (Im also following this closely, since I still have a 28 super thats in a box, needing me to finish it)

 

[powerking]

....While your at it, ditch that base gasket and make one out of an aluminum can and bring that squish down to .020, and watch that compression go right up.....

 

[SteveoSupremo]

That looks a lot better than the first shot you had, so definite progress.
Good work so far, the folks here will help bring you the rest of the way in. (Im also following this closely, since I still have a 28 super thats in a box, needing me to finish it)

Good luck I have all the IPL, manual, owners guide if you need them.

Thanks the oil was some cheap stuff my buddy probably picked up at Walmart or somewhere. That fuel was fresh earler in the day the fuel we used was definitely old maybe 3 - 4 months possibly longer and the same thing with the oil cheapest chainsaw oil from a hardware store.

I have most all of the parts I need on order. the only thing I can't find is a manifold (the rubber boot) OEM from a stihl dealer is $35 which is as much as an after market meteor piston. which by the way Northwood Saw has the best prices!!! currently about $75 for new piston, carb kits (both I'll remove the one I don't need), impulse, fuel line, and fuel filter.

after I was cutting for about 15 min, when I would pull the trigger the saw seemed to loose power and stall. turning up (1/16 of a turn) the high end carb adjustment and i was cutting away. Looking back I should have noticed that at idle the chain was spinning pretty good. my guess is the carb is way out of adjustment.

putting a soda can gasket sounds interesting I don't think I'm going to try it right away maybe if I pick up another project. what is the muffler mod? just leaving the spark arrester out?

 

[SteveoSupremo]

Another question.

How do I know if the hoses, elbows etc are bad? they are soft and pliable and I don't see any cracks.

my reason is the elbow/manifold is going to run me as much as the piston!

any thoughts?

thanks
Steve