028 AV Super project

[Maintenance supervisor]

The super is the only one with the domed piston.

 

[Mad Professor]

Good to see the Cyl cleaned up they are NLA.

Stihl matched P + C sizes and stamped them on both. The replacement pistons were stamped A/B and sort of a compromise that fit both.

I can't remember if A, B, or C was the larger/smaller? Maybe some old time stihl guys remember?

I know Meteor pistons are sized too. You want about 0.002-0.0025" clearance.

$tihl i$ very proud of their pi$ton$. 2019 price was $97!!!

 

[flatsfisher]

Good to see the Cyl cleaned up they are NLA.

Stihl matched P + C sizes and stamped them on both. The replacement pistons were stamped A/B and sort of a compromise that fit both.

I can't remember if A, B, or C was the larger/smaller? Maybe some old time stihl guys remember?

I know Meteor pistons are sized too. You want about 0.002-0.0025" clearance.

$tihl i$ very proud of their pi$ton$. 2019 price was $97!!!

are you saying 0.002-0.0025" piston diameter smaller than bore or 0.002-0.0025" each side of cylinder?

I have a cylinder diameter of .46mm (1.811") and the meteor "A" piston is 45.96mm (1.809") which is .002" smaller than my cylinder bore.

 

[flatsfisher]

finally, back to this saw. been a busy week. should this drive sprocket be replaced or does it have good use left in it?

 

[flatsfisher]

this muffler looks really restrictive. is anyone taking the guts out of either of these 2 pieces and then adding a 2nd outlet? what is the best way to mod this? thanks.

 

[flatsfisher]

the exhaust gets from the exhaust port to the outer half through these holes. there are also holes on the other side of the snorkel or whatever it is.

 

[flatsfisher]

this is the only outlet for the exhaust. seems pretty meager.

 

[flatsfisher]

ok, last thing for now. since this saw had the rings stuck in the piston, I'm going to kit the carb and replace the impulse line. this saw has what I think of as the "beaded" style of line. when I did my 036, I got a 2 pack of NOS OEM impulse line and it is just regular thick line. any issues if I use the smooth type line?

 

[scottr]

finally, back to this saw. been a busy week. should this drive sprocket be replaced or does it have good use left in it?
View attachment 1005511

My 044 owners manual says to replace the sprocket when the wear is 0.020" .

 

[scottr]

the exhaust gets from the exhaust port to the outer half throughView attachment 1005515 these holes. there are also holes on the other side of the snorkel or whatever it is.

That is called a diffuser .
What diameter are the 20 holes in that diffuser ?

 

[flatsfisher]

thanks for responding Scott. the 20 holes are each 6mm dia. the exhaust inlet in the muffler is 15x25mm. the exhaust port in the cylinder is 15x26mm. the 2 little half-moon exhaust outlets in the muffler outer half are approx. 3mmx12mm, if that.

 

[scottr]

this is the only outlet for the exhaust. seems pretty meager.
View attachment 1005516

The area of the two louvers total about 0.115 square inch .
A 5/8" inside diameter pipe (0.306 square inch area) would be better for your 3.1 cubic inch engine .
Maybe a 5/8" copper elbow brazed .

 

[cookies]

That piston damage is from running lean, straight gassed pistons are scored all over not just the exhaust side. Betting someone played with the carb setting it too lean or a fuel delivery issue since the case passed the vac/pressure test. I for sure would tear it all the way down and install new gaskets and crank seals, you might find the crank bearings need attention and the case needed internal cleaning. I would not hesitate to add a few holes to the front of the Swiss cheese muffler baffle and open up the entire section covered by the exhaust outlet plate as long as the screen still blocks the flames exit.

 

[flatsfisher]

I did clean out the crankcase and oiled crank and rod bearings. leaning towards leaving the crank seals as they are not leaking. will think about it though.

 

[HarleyT]

finally, back to this saw. been a busy week. should this drive sprocket be replaced or does it have good use left in it?
View attachment 1005511

I would wait until you put a new chain on it.

 

[Maintenance supervisor]

Tie straps of the chain are hitting the spurs of the sprocket, time to change it out. Oregon sells a rim sprocket drum that comes with the bearing and oil pump drivr gear its a great set up and I have swapped all mine over to it.
I drill two 1/2" holes in the front of the internal baffle of the muffler and have used a gill slit on the back half of the muffler body to help it breath.
Crank seals should be replaced if orginal, I've never seen or heard of an 028 with bad lower end bearings? But it could happen I suppose.

 

[flatsfisher]

I did clean out the crankcase and oiled crank and rod bearings. leaning towards leaving the crank seals as they are not leaking. will think about it though.

chain and bar look new, and the guy said he bought them right before the saw seized.

 

[flatsfisher]

Tie straps of the chain are hitting the spurs of the sprocket, time to change it out. Oregon sells a rim sprocket drum that comes with the bearing and oil pump drivr gear its a great set up and I have swapped all mine over to it.
I drill two 1/2" holes in the front of the internal baffle of the muffler and have used a gill slit on the back half of the muffler body to help it breath.
Crank seals should be replaced if orginal, I've never seen or heard of an 028 with bad lower end bearings? But it could happen I suppose.

thanks. the crank makes a very slight noise when spun, may be friction from the seals. doesn't sound metallic.

 

[ballisticdoughnut]

Good to see the Cyl cleaned up they are NLA.

Stihl matched P + C sizes and stamped them on both. The replacement pistons were stamped A/B and sort of a compromise that fit both.

I can't remember if A, B, or C was the larger/smaller? Maybe some old time stihl guys remember?

I know Meteor pistons are sized too. You want about 0.002-0.0025" clearance.

$tihl i$ very proud of their pi$ton$. 2019 price was $97!!!

“A” would be the smallest bore cylinder, as well as smallest diameter piston. The piston and cylinder must match to get the proper clearance as I’m sure you know. So A piston with A cylinder, B piston with B cylinder and so forth.

 

[flatsfisher]

That piston damage is from running lean, straight gassed pistons are scored all over not just the exhaust side. Betting someone played with the carb setting it too lean or a fuel delivery issue since the case passed the vac/pressure test. I for sure would tear it all the way down and install new gaskets and crank seals, you might find the crank bearings need attention and the case needed internal cleaning. I would not hesitate to add a few holes to the front of the Swiss cheese muffler baffle and open up the entire section covered by the exhaust outlet plate as long as the screen still blocks the flames exit.

went ahead and ordered NOS OEM crank seals from ebay last night. had to do some searching to find some priced right. when I took the clutch hub off the crank last night to see the right-side crank seal, most of the small amount of noise I heard before when turning the crank went away. the crank and big end rod bearings are smooth and quiet.