MS390 / 039 pop up piston

[Terry Syd]

I've got a Huztl jug. I'll put some clay on the piston and check the clearance, but I expect it will be alright (hopefully it will be TOO tight and I have to trim a bit). The Huztl jug has a central combustion chamber.

 

[CR888]

Besides the compression bump I wonder how the new pop up's affect combustion and transfer flow into the cylinder. Kinda want to find a cheap non running 290 & build a nice 390. I like the ignition module swap Terry did, clever.

 

[Terry Syd]

The lightweight NK bar was the nicest addition. It changed the whole balance of the saw to where it was 'tail heavy'. With both hands supporting the powerhead, the saw feels a lot lighter than it is. Plus it is more nimble, great for limbing. The extra 15% in cutting speed was a secondary benefit.

Putting a Husky bar on the saw was a lot of work, however I remember seeing a NK bar that would fit on a Stihl. If someone needs to get a new bar for their saw, they might want to look into getting a NK bar.

In Oz, even these old crappy saws can be expensive. I was lucky and picked this one up for $50. I probably will have close to $300 in the saw by the time the piston goes in.

 

[MustangMike]

How long, how light, and what do they cost? The Stihl 20" E bar is almost as light as a Sugi and cost about 1/2. I love em. I'm also very happy with the 18" on the 261.

 

[Terry Syd]

I had the 20" Husky bar and chains, after eye balling it, I figured it was do-able, but a lot of work. When I first bolted the NK bar on to see how it might fit, I immediately noticed the difference in handling. That was it, I had to swap the bar. I got rid of the 20" solid steel 3/8" bar and went to the laminated NK bar. It just made it a great handling saw.

I think it was on Bailey's that I saw the Stihl bar.

That Chinese coil with the 4 degree retard for starting was less than A$20 delivered.

 

[MustangMike]

So, you are talking about the Woodland Pro Narrow Kerf in 325 ??? On my 261 I am running 3/8 square file, and it eats wood!

 

[beaglebriar]

I had the 20" Husky bar and chains, after eye balling it, I figured it was do-able, but a lot of work. When I first bolted the NK bar on to see how it might fit, I immediately noticed the difference in handling. That was it, I had to swap the bar. I got rid of the 20" solid steel 3/8" bar and went to the laminated NK bar. It just made it a great handling saw.

I think it was on Bailey's that I saw the Stihl bar.

That Chinese coil with the 4 degree retard for starting was less than A$20 delivered.

They are very nice on a small saw. I've been using one on my 353 and have been real happy. I plan to get one for the 346 as well. Never thought I'd go back to .325 but there's just something about the NK.

 

[Terry Syd]

but there's just something about the NK.

Yeah, it just needs to be set up right. The stock cutting angle (raker depth) is probably less than 4 degrees. The chain really needs around 6 degrees to show its true value. I think the small stock cutting angle is because the chain was designed to be used on small saws.

Just a note, the NK chain is just as strong as a regular .325 chain. The chain will fail (more than 800 lbs of weight) at the rivet hole in the driver links. The driver links are the same for both NK and regular .325. One of the top racers in Oz uses the NK chassis to race in the 77cc class (piped saws). He just takes the full chisel cutters off a regular .325 chain and puts them on the NK chassis. It is lighter and he doesn't have to do any extra work like 'dog boning' the links or grinding the rivets.

I'm running an 8-pin on the saw, which is a 14% overdrive over a 7-pin. Since the NK cuts 15% faster, the saw doesn't even notice the bigger sprocket. I had a 9-pin on it for a while, but I kept using the lightweight saw for everything, including bucking big Ozzie hardwood, so I dropped back to the 8-pin.

I couldn't find the 20" NK bar for Stihls on Bailey's website. I remember something being available, but I don't know where it was.

 

[Terry Syd]

I am running 3/8 square file, and it eats wood!

Mate, I cut mostly Ozzie hardwood that is rarely clean. I only have one full chisel chain for my Chinese 365 (77cc) that I use for racing or showing off, everything else is semi-chisel. I'd love to run square file, I just need someone to keep sharpening it for me...

 

[CR888]

I have maybe 10 full chisel chains & about 10 loops of CL square 3/8 the other 3 rolls and 150ish loops are all semi chisel. It's just the way it has to be.

 

[beaglebriar]

I got one of these pistons today. Don't have a saw to put it in, nor do I own a Stihl. Just wanted to check it out.

 

[CR888]

I got one of these pistons today. Don't have a saw to put it in, nor do I own a Stihl. Just wanted to check it out.

CAD confirmation right there.

 

[beaglebriar]

CAD confirmation right there.

Don't judge me...

 

[RI Chevy]

Well....... Time to go buy a Stihl 390 used, tare it down and put that pistola in and see what she does. Compare stock and any changes with vids for us.
All in the name of saw science for the good of the order. Lol

 

[CR888]

I don't own any Stihl farm/ranch saws & I want one too! My eyes are peeled looking for a cheap 291. There is a cheap Husky 450 rancher on AS just posted for $75 bucks. Runs but needs oiler fixed. Someone grab it!

 

[Adirondackstihl]

I don't own any Stihl farm/ranch saws & I want one too! My eyes are peeled looking for a cheap 291. There is a cheap Husky 450 rancher on AS just posted for $75 bucks. Runs but needs oiler fixed. Someone grab it!

Not sure what your 291 intentions are, but if it’s to put a 390 pop up in, you’re gonna be disappointed. I believe the 291 is a strato saw with a different chassis.
Someone correct me if my wrong

 

[71dart]

Mine started out as a clean 029 super that a guy I was working for gave me. It had a fried top end but I bought an excellent condition OEM 039 top end from a guy in the trading post here ( or maybe it was on AS).
I've opened up the muffler and i'm running an ms 460 carb on it.
I just got the pop up in it and I'm waiting for the sealant to cure overnight. The OEM compression was 140psi. We'll see what it blows tomorrow....

 

[Terry Syd]

Something to remember if anyone mods an early 029 is that the oiler only has a .4mm stroke. You can pick up a Chinese 390 oiler off of Ebay that has a .88mm stroke.

 

[Adirondackstihl]

Something to remember if anyone mods an early 029 is that the oiler only has a .4mm stroke. You can pick up a Chinese 390 oiler off of Ebay that has a .88mm stroke.

I’ve yet to personally hold a Chinese oiler in my hand that was worth 2 cents. Machining tolerances are absolutely atrocious.
Not saying there aren’t good ones out there.....but I’ve yet to see one that I’d use.

 

[Fruecrue]

I’ve yet to personally hold a Chinese oiler in my hand that was worth 2 cents. Machining tolerances are absolutely atrocious.
Not saying there aren’t good ones out there.....but I’ve yet to see one that I’d use.

There’s one in my Chinese 066, oils just fine.
That’s the extent of my experience with AM oil pumps, however.