Stihl 028 AV Super repair

[acarpenterdad]

No way around it. Take some Aleve for the arthritis. WD-40 and a couple grits of wet dry sand paper. I go 150, 220, 320 then finish off with red scotch brite. It's going to take several hours. This has been my experience. Supposedly you can use muriatic acid and those long qtips but I haven't tried it.

I'll take my naproxen straight! thanks!

 

[Mad Professor]

Is your cylinder a B size like your new piston?

 

[acarpenterdad]

Is your cylinder a B size like your new piston?

Yes!

 

[Mad Professor]

Yes!

That's good news. Check your clearance anyway. Takes ~ 5 minutes with feeler gauges . Should be ~ 0.002-0.003".

Let us know what you have for clearance.

I'm curious if Meteor stuff matches up to OEM Stihl? $tihl got rather proud on their pi$ton price$ again. I need a piston for a 064......

 

[acarpenterdad]

Wil d

That's good news. Check your clearance anyway. Takes ~ 5 minutes with feeler gauges . Should be ~ 0.002-0.003".

Let us know what you have for clearance.

I'm curious if Meteor stuff matches up to OEM Stihl? $tihl got rather proud on their pi$ton price$ again. I need a piston for a 064......

will do

 

[acarpenterdad]

Slip a feeler gauge between the intake piston skirt and the bottom of the cylinder while you slide it in.

You should be able to fit a .001-.002 between the piston and the cylinder. .003 is a bit loose, especially for a new slug. Anything more is no good.

The ring gap is easy. Insert the ring and push above the exhaust roof with the piston crown, just make sure you don’t push it to the top. Measure the gap with a feeler gauge. Usually .007 or better is ok for your bore. There’s a formula I forget that’s easily found online. It’s alway good to check, but meteor pistons come with caber rings (same company) and I have yet to find a single one that was off. It’s a quality product. I stopped checking with cabers altogether.

Ok. I can get the .0015 in between the piston and cylinder. Cant do the .002.i can get an .004 in the ring gap, but not an .005

 

[Mad Professor]

Ok. I can get the .0015 in between the piston and cylinder. Cant do the .002.i can get an .004 in the ring gap, but not an .005

I think you are right on the edge of tight on the P/C, there is 0.0005" between the two gauges. I think 0.002" would be great.

I measured with mics some NOS 038S and 038M P/C. They were 0.002" but also have a bigger bore (46 vs 50/52 mm). A NOS Italian tecomec 038M had 0.0025"

Long ago a member (Lakeside53) commented on ring end gap, refering to 044 (50mm bore). He measured 0.005-0.008" NOS OEM on a bunch of saws. I think you are O.K. there too.

I'd like to hear from pioneerguy600. He actually has measured more saws than myself. I have to borrow quality mics

IMHO looks like a good tight fit.

None of the stihl service manuals I've seen, on saws mentions these clearances. I gue$$ they just want to $ell new part$.

I'd be most skeptical of what comes out of China. Maybe some here could start checking clearances, if they have the tools, and posting what they find.

When I checked the 038 assys I checked P/C clearance, piston taper, assy mass, and wrist pin clearance. I lost the notes on assy mass when an old computer crashed (but I think I posted it here 2008). I didn't check ring gaps as the P/C assys were matched sets, and rings already installed

 

[acarpenterdad]

Good to know! Now i will work on cleaning the cylinder better, measure the squish, a get a set of snap rings for the "knuckle".

 

[drf255]

Just got the piston! It was in the mail box. Crap! No clips with it and I lost one taking it out...

Message your seller that it came without clips. See if they send. They should have been in there.

Meteor makes a great product, but the pins and clips aren’t always an oem match. Oem clips used thinner wire (in general) and the grooves are correspondingly deeper/wider than oem on the meteor slugs. The piston pins can also be longer of shorter. I use the meteor clips for meteor pistons, they are of good quality.

@pioneerguy600 , can you comment on clearances?

 

[acarpenterdad]

Message your seller that it came without clips. See if they send. They should have been in there.

Meteor makes a great product, but the pins and clips aren’t always an oem match. Oem clips used thinner wire (in general) and the grooves are correspondingly deeper/wider than oem on the meteor slugs. The piston pins can also be longer of shorter. I use the meteor clips for meteor pistons, they are of good quality.

@pioneerguy600 , can you comment on clearances?

I will do that! Thanks

 

[pioneerguy600]

Message your seller that it came without clips. See if they send. They should have been in there.

Meteor makes a great product, but the pins and clips aren’t always an oem match. Oem clips used thinner wire (in general) and the grooves are correspondingly deeper/wider than oem on the meteor slugs. The piston pins can also be longer of shorter. I use the meteor clips for meteor pistons, they are of good quality.

@pioneerguy600 , can you comment on clearances?

For the piston clearance it is most critical at the crown as it expands more there due to the mass of material in that location so .0025 - .003 is enough there. The ring gap for an 028 using ductile iron rings should be .005 or more for heat expansion. A tighter gap can be run if a saw is never exposed to a extended heavy cut time but most saws are run too hard and hot so best to be on the safe side. I have not used a Meteor piston in an 028 so far but drf255 is correct in that the wrist pin and clips can be different from OEM in their pistons in general, I would try OEM clips in a Meteor but with careful examination of the fit and suitability. The groove where the clip is retained would need to be a good match and position the clip so that the wrist pin could not slide out over the clip as I have heard from others of this happening when using some AM pistons. For the most part Meteor pistons are fine for rebuilds and the components such as the rings, pin and clips are good enough to be used, they work in most applications but it is still up to the installer to make sure all bits fit properly.

 

[acarpenterdad]

For the piston clearance it is most critical at the crown as it expands more there due to the mass of material in that location so .0025 - .003 is enough there. The ring gap for an 028 using ductile iron rings should be .005 or more for heat expansion. A tighter gap can be run if a saw is never exposed to a extended heavy cut time but most saws are run too hard and hot so best to be on the safe side. I have not used a Meteor piston in an 028 so far but drf255 is correct in that the wrist pin and clips can be different from OEM in their pistons in general, I would try OEM clips in a Meteor but with careful examination of the fit and suitability. The groove where the clip is retained would need to be a good match and position the clip so that the wrist pin could not slide out over the clip as I have heard from others of this happening when using some AM pistons. For the most part Meteor pistons are fine for rebuilds and the components such as the rings, pin and clips are good enough to be used, they work in most applications but it is still up to the installer to make sure all bits fit properly.

So do I need to make the ring gap bigger?

 

[pioneerguy600]

So do I need to make the ring gap bigger?

Your call, I know of guys that have run them with less but they were never subjected to much heat, just occasional light duty around the yard. If you plan on cutting /bucking wood over 12" diameter then I would suggest the .005 ring end gap.

 

[Mad Professor]

Concerning piston clearance. The OEM 038 pistons I measured all had 0.005-0.006" of taper crown to skirt. A new piston with 0.002" clearance at the skirt had at least 0.007" clearance at the crown.

This taper is built in as @pioneerguy600 due to piston expansion. You still need proper clearance at the skirt.

@acarpenterdad what be your ~ piston clearance at the crown?

A couple minutes with a small file should get you ~0.001-0.002" more ring end gap. Don't leave any burrs.

P.S. @pioneerguy600 , what do you like to see for end gaps with larger saws? 70cc 90cc. I might be doing a 064 and have a line on some free 044s

 

[acarpenterdad]

I will get a top measurement and see. Can i get that through the exhaust port? I have a diamond microfile set, should be able to get a thousandth off easily enough for the rings.

 

[acarpenterdad]

Your call, I know of guys that have run them with less but they were never subjected to much heat, just occasional light duty around the yard. If you plan on cutting /bucking wood over 12" diameter then I would suggest the .005 ring end gap.

Most of the wood i get is over 12". Last year i got a 16' section of oak that went from 36" on one end to 52" on the other.

 

[Mad Professor]

I will get a top measurement and see. Can i get that through the exhaust port? I have a diamond microfile set, should be able to get a thousandth off easily enough for the rings.

The cylinder should not have any taper. Cylinders on old equipment w/cast iron liners would wear and have taper or get out of round. Those you could bore out and fit oversize piston.

You can measure crown clearance at the bottom of cylinder with piston upside down. Then compare that with skirt to get taper.

 

[pioneerguy600]

Concerning piston clearance. The OEM 038 pistons I measured all had 0.005-0.006" of taper crown to skirt. A new piston with 0.002" clearance at the skirt had at least 0.007" clearance at the crown.

This taper is built in as @pioneerguy600 due to piston expansion. You still need proper clearance at the skirt.

@acarpenterdad what be your ~ piston clearance at the crown?

A couple minutes with a small file should get you ~0.001-0.002" more ring end gap. Don't leave any burrs.

P.S. @pioneerguy600 , what do you like to see for end gaps with larger saws? 70cc 90cc. I might be doing a 064 and have a line on some free 044s

I like to see .006-.007 0n the 044`s and .007 - .008 on the 066 saws due to them being used hard and often heated in long endurance cuts.

 

[acarpenterdad]

The cylinder should not have any taper. Cylinders on old equipment w/cast iron liners would wear and have taper or get out of round. Those you could bore out and fit oversize piston.

You can measure crown clearance at the bottom of cylinder with piston upside down. Then compare that with skirt to get taper.

That's a fine way to do it! The thought never occured to me...

 

[acarpenterdad]

Update: vendor sent new snap rings, in holding pattern....