MS390 / 039 pop up piston

[Terry Syd]

Well, you can always purchase an OEM piston from Stihl that will bump the flow up to the .88mm a stroke. Either way, if you are going to run a long bar or use an 8-pin, the extra oiling makes a difference. Mine pumps out heaps of oil and makes a mess, but I like it that way.

 

[MustangMike]

The oiler on my Chinese 660 works just fine.

 

[hseII]

Have a number of them in the field. Rebuilt, some with meteor pistons and cleaned up cylinders, some with the older Chinese kits.
Plenty of hours on them with happy people running them. I'd buy a nice looking carcass and build one in a heart beat.

Baby Uncle has 2, & would rather run either of them than his MS650.

I just recently sold my Stihl 029. I ran it hard for over 20 years. Much harder than it was intended for. Piston and cylinder looked brand new. It was a clean saw that served me well. I always intended to make it into an 039, but I now have all pro saws.

I gave my FIL my 1st saw, a Muff Modded 029 Supa that has been a great saw.

I thought about putting a Caspian winch on it whenever it comes back to me,( not that I want it like that, but his health is getting to where he’s too seasoned to fool with a saw), but this seems to be another option.

Thank You.

 

[71dart]

Well, I ran a tank through my saw with the pop up yesterday and it felt strong (for what it is) and snappy.
The stock compression was 140psi and now it's 148 psi so not a huge jump but I'll be interested to see if that climbs as the rings break in.
I bet for the average fire wood cutting guy, if this was his only saw, he'd be thrilled to run it.

 

[Terry Syd]

A 5% increase in compression on your saw. If you have a decomp on the saw, you can remove the washer under it to reduce the head volume some more. I do it to both the decomp and the spark plug. The tighter the combustion chamber, the more effect the pop-up piston will have.

I've never checked the compression on my saw, anybody know what the stock compression is on one of these 039/390 jugs?

 

[Fruecrue]

A 5% increase in compression on your saw. If you have a decomp on the saw, you can remove the washer under it to reduce the head volume some more. I do it to both the decomp and the spark plug. The tighter the combustion chamber, the more effect the pop-up piston will have.

I've never checked the compression on my saw, anybody know what the stock compression is on one of these 039/390 jugs?

I’ve seen large variations in compression on these.

 

[71dart]

No decomp on my saw.
My saw has an OEM 039 cylinder and had an OEM piston before I put the pop up in it. That was the 140 psi I noted above.
Fruecrue's was at 168psi before the swap and it looks like an OEM cylinder in one of his pics. So they may vary a lot.
I guess compression testers can vary a lot too although I use a snap on tester as does Fruecrue.

 

[Fruecrue]

No decomp on my saw.
My saw has an OEM 039 cylinder and had an OEM piston before I put the pop up in it. That was the 140 psi I noted above.
Fruecrue's was at 168psi before the swap and it looks like an OEM cylinder in one of his pics. So they may vary a lot.
I guess compression testers can vary a lot too although I use a snap on tester as does Fruecrue.

Squish only varied .007” between our saws.
Have you put a degree wheel on yours?

 

[71dart]

No, I haven't.
I don't have a degree wheel but it seems like this would be a good opportunity to rig one up!

 

[Fruecrue]

Dropped and bucked a 16”x 60’ tall ash tree today with the 039, 16” .325 semi- chisel.
Never stuttered or bogged.
Clam slam or professional saw, doesn’t matter, got the job done with authority.
Glad I took it before the ants or the emerald ash boarer.

 

[hseII]

Dropped and bucked a 16”x 60’ tall ash tree today with the 039, 16” .325 semi- chisel.
Never stuttered or bogged.
Clam slam or professional saw, doesn’t matter, got the job done with authority.
Glad I took it before the ants or the emerald ash boarer.
View attachment 99429

Why you running a 16” .325” on a 64cc saw?

 

[blsnelling]

No decomp on my saw.
My saw has an OEM 039 cylinder and had an OEM piston before I put the pop up in it. That was the 140 psi I noted above.
Fruecrue's was at 168psi before the swap and it looks like an OEM cylinder in one of his pics. So they may vary a lot.
I guess compression testers can vary a lot too although I use a snap on tester as does Fruecrue.

What's your elevation there?

 

[Fruecrue]

Why you running a 16” .325” on a 64cc saw?

Because it’s fast.
I have bigger saws with bigger bars. They don’t fit into this thread. I could have dropped it with my ported 026...

I picked the right saw and “blade” ( forgive me @Jon1212 ) for the task at hand.

 

[hseII]

Because it’s fast.
I have bigger saws with bigger bars. They don’t fit into this thread. I could have dropped it with my ported 026...

I picked the right saw and “blade” ( forgive me @Jon1212 ) for the task at hand.

I was just thinking about hanging a 32” Skip on one & see how it compares to my 461.

Long Bars sure are nice when you get older, or in my case, busted up.

Don’t have to bend over as much.

 

[Fruecrue]

I was just thinking about hanging a 32” Skip on one & see how it compares to my 461.

Long Bars sure are nice when you get older, or in my case, busted up.

Don’t have to bend over as much.

She’ll pull it.

 

[Jon1212]

Because it’s fast.
I have bigger saws with bigger bars. They don’t fit into this thread. I could have dropped it with my ported 026...

I picked the right saw and “blade” ( forgive me @Jon1212 ) for the task at hand.

No worries here, bruh! After selling OPE for the last year and some change, I'm pretty well desensitized to the "blade" reference. Unless of course it's the customer wanting a new "blade" for his (model) 20" Stihl......

I was just thinking about hanging a 32” Skip on one & see how it compares to my 461.

Long Bars sure are nice when you get older, or in my case, busted up.

Don’t have to bend over as much.

I'll run a 28" and full comp on mine this week, and report back. That's the same set up I run on my 461.

Long bars are even better when you're older, and very busted up.

 

[Jon1212]

She’ll pull it.

How did it oil?

 

[hseII]

No worries here, bruh! After selling OPE for the last year and some change, I'm pretty well desensitized to the "blade" reference. Unless of course it's the customer wanting a new "blade" for his (model) 20" Stihl......



I'll run a 28" and full comp on mine this week, and report back. That's the same set up I run on my 461.

Long bars are even better when you're older, and very busted up.

461 is where it’s at, isn’t it Cousin.

 

[Fruecrue]

How did it oil?

Meh.
I wouldn’t call it good to go, but I wouldn’t say it’s a no go either.

 

[Jon1212]

461 is where it’s at, isn’t it Cousin.

I'm really liking it. I probably have 12-15 tanks through it, so far.