Olympyk 980 Woods Port

My $250 980 needs some TLC, and as long as it is in the shop, it might as well get a woods port, too. Right ?

The gas tank developed a crack by the handle. This is a highly stressed spot and it could be a problem to make a lasting repair.


I've never repaired a plastic gas tank before, but I've had excellent luck repairing a variety of plastic with 3M 2216. I sanded the area and cleaned with acetone before applying the epoxy, and reinforced it with a piece of fiberglass window screen (it was handy).


Degree wheel glued on with a few dabs of contact cement.
Exhaust duration = 156 degrees
Intake duration = 148 degrees
Blowdown = 17.5 degrees
Squish = 0.038"

Very mild port timing, eh ? Which is a good thing, because it gives the modder more options.


The saw had been sucking a little sawdust recently because this boot connecting the air filter to the carb wasn't sealing well. It's supposed to be soft, springy rubber, but over the years it became stiff and uncooperative. This new boot came from Baileys (thanks, Grande Dog).


The cylinder gasket appears to be made of paper -- and no, the bolts were not particularly tight, but they had been loctited.

Looking at the intake port. All of the Oly ports are nearly rectangular (sorry, Brad, but they do seem to work OK). Some light rubbing around the intake due to the leaky filter boot. Good thing I caught it in time.


Transfer ports are bigger and deeper than on a Stihl 066 ! ! ! Upper transfer is already swept back toward the intake side. Unless I decide to tweak the blowdown time, I don't plan to touch the transfers, because they are perfect.

Exhaust side. A fair amount of carbon gunk on the exhaust port, typical when the saw sucks sawdust. A couple of trivial scratches below the port. Bore measured 2.0468" - 2.0491" with a telescoping gage and a mic. Nominal diameter is 52mm (2.047"). Variations could be wear/warping or it could be my measuring technique. Anyway, I call it good.


Looking at the exhaust side of piston. One trivial scratch. Skirt has "wings" at bottom. Marked "Vertex 1116", I'm guessing it is OEM ? BTW, circlips were dual wing style with surprisingly little tension.


Intake side. Scuffing on skirt, carbon on top land. Typical signature of sawdust poisoning.


Carbon on top of piston and also on combustion chamber, again typical when sucking sawdust.


Port map. Nearly rectangular ports.


Piston skirt mic'd 2.0432" - 0.20445", despite the intake side scuffing. I'm inclined to reuse the piston since the clearance is reasonable.

12mm piston pin. Center-of-pin to top-of-piston is 23mm. Piston 42.5mm tall. Top land 3.6mm thick. I heard a rumor that it interchanges with a Stihl 064 piston, but not sure about that.

Ring gaps were 0.018" and 0.023". Definitely need new rings.

Compression was 145 psi last year, but today it was 135 psi, probably due to sawdust-related scuffing.

I should have leak tested before tearing it down, but I didn't have anything to seal the intake. There have been no leak symptoms. I'll leak test it somewhere along the way, just to be sure.

The tentative plan is for new rings, a mild woods port, and a mild pop-up. I'll try to find a carb kit even though the carb has not been a problem.

I like most of the Efco design, compared to say, my Stihl 066. More compression, even after 11 years. Sane port timing. Easier to raise compression due to generous 0.038" squish. Too bad Efco doesn't make a milling saw.

Things I don't like are the air filter boot and the handle attaching to the gas tank rather than the crankcase. And I wish it had a full wrap handle.

I was talking to the Canadian Efco distributer this week about the 199. Its still available but it was selling in too few of numbers for them to continue bringing it or parts in. Was thinking of one for my mill. I am going to try the 181. I am only milling 10 inch softwood.

Stihl Crazy said:

I was talking to the Canadian Efco distributer this week about the 199. Its still available but it was selling in too few of numbers for them to continue bringing it or parts in. Was thinking of one for my mill. I am going to try the 181. I am only milling 10 inch softwood.

Click to expand...

Bolt an 090 onto it and don`t look back. LOL
Had my 090`s out on the weekend and I can easily see why they make excellent milling saws. When the 090AV turns over from fourstroke to two stroke in the cut it becomes quite a ride. LOL
Pioneerguy600

I got one of those 980's new I modded it and it rocks, but I need to put it in wood again. I ran it at Woodjunkies GTG in 06? The filter arrangement leaves something to be desired, but otherwise, it's a good 80cc saw and built like a brick chit outhouse. If you want it, lets make a deal!
John

pioneerguy600 said:

Bolt an 090 onto it and don`t look back. LOL
Had my 090`s out on the weekend and I can easily see why they make excellent milling saws. When the 090AV turns over from fourstroke to two stroke in the cut it becomes quite a ride. LOL
Pioneerguy600

Click to expand...

I have a new 880 for big cuts. Just seems to be overkill to make 2x4's with.

Yukonsawman said:

I got one of those 980's new I modded it and it rocks, but I need to put it in wood again. I ran it at Woodjunkies GTG in 06? The filter arrangement leaves something to be desired, but otherwise, it's a good 80cc saw and built like a brick chit outhouse. If you want it, lets make a deal!
John

Click to expand...

What you got in mind?

Stihl Crazy said:

I have a new 880 for big cuts. Just seems to be overkill to make 2x4's with.

Click to expand...

It would be overkill big time for milling small softwood.
Pioneerguy600

Made a dozen 8 foot 4x4's Sat using an old Jon 625. Worked great. I also have a 2095 that needs a piston so I do have other options.

olympyk

Anyone know where I can get a piston and ring for a 980 and possibly a cylinder.
jason

mtngun,

When I saw your thread title, I couldn't get here fast enough. After some other saw projects are done, I'm thinking that my 970 will be next for some mild porting...if the other projects work out and I feel confident enough. I'll be following this thread with interest and it will be bookmarked.

Kevin

jsk said:

Anyone know where I can get a piston and ring for a 980 and possibly a cylinder.
jason

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I ordered Caber rings from the guy in Greece. The OEM rings were 1.5mm thick, but some of the aftermarket 52mm pistons use 1.2mm rings, so be sure to verify.

Wouldn't swear to it, but the 980 piston appears to have the same specs as an 064 piston, so if I needed a piston, I'd try a Meteor for the Stihl 064. I've listed my OEM piston specs, if you need me to measure anything else while it's apart, just holler.

I haven't seen an aftermarket cylinder for the Efco saws. Baileys can get you Efco parts if you ask, and possibly AS member Olyman. Unless the jug is bargain priced, an old 980 may not be cost effective to rebuild.

KMB, it looks like it is going to be real easy to get more power out of this saw, since it is tuned so mildly and had decent compression even with 0.038" squish.

I found a carb kit on ebay and it's on the way, a K15-WJ. Our sponsor CM Small Engines also stocks the kits.

I've been making a list of things I can do while waiting for the rings:

-- cc the chamber

-- leak test (like I should have done earlier )

-- mod the muffler ?

-- pop-up, shave base, make gasket

-- mild port job

mtngun said:

My $250 980 needs some TLC, and as long as it is in the shop, it might as well get a woods port, too. Right ?

The gas tank developed a crack by the handle. This is a highly stressed spot and it could be a problem to make a lasting repair.

Click to expand...

If there is sufficient room to carve, you can probably inlay a "butterfly key" (like they do in woodworking) made out of the same material if you have an extra tank laying around. Along with epoxy, it should stop the crack from splitting more.

980

Thanks I didnt know that a 064 piston is the same sixe. Ill have to try. Im gonna try to clean up the cylinder and just put new piston and rings in it and see what happens. I hope a 064 piston fits that would make it easy.
jason

CC'd the combustion chamber.

First, I cleaned the carbon off the piston and off the combustion chamber.

Then pushed the piston (with rings) to the top of the cylinder until it came to rest against the squish band.

Filled a 10cc syringe with water up to the 10cc mark. Made sure there were no air bubbles in the syringe.

With the jug held so that the spark plug hole was pointing straight up, I dribbled water into the plug hole until the bottom thread was flooded. Record CC of water used, dump water and blow out jug, repeat at least three times, take an average. The amount of water required is what I call the "zero squish chamber volume."


Zero squish chamber volume = 6.7 CC

Each 0.010" squish is 0.54 CC.

It originally had 0.038" squish. 3.8 times 0.54 CC = 2.05 CC.

Total OEM chamber volume = 6.7 CC + 2.05 CC = 8.75 CC.

OEM uncorrected compression ratio (UCCR) = 80.7 CC divided by 8.75 CC = 9.2:1

Compare that to 8.0:1 - 8.2:1 on current Stihl 066/660's. Chiiiit, no wonder it is so hard to get good compression on my 066.

Let's figure out the chamber volume with 0.025" squish. 2.5 * 0.54CC = 1.35CC

Chamber volume @ 0.025" squish = 1.35 CC + 6.7 CC = 8.05 CC

UCCR = 80.7 CC divided by 8.05 CC = 10:1 I like.

Estimate PSI at 0.025" squish, compared to 140 psi at 0.038" squish.

PSI/140 = 10/9.2

Estimated PSI at 0.025" squish = 152 psi

I'd like to have 160 - 170 psi, so it looks like a pop-up will still be required.

Estimate UCCR to achieve 165 psi, compared to 140 psi at 9.2 UCCR.

UCCR/9.2 = 165/140

UCCR = 10.8

Chamber volume required for 10.8:1 UCCR is 7.4 CC.

I'll try a 0.025" pop-up and re-measure the chamber volume. I'm guessing 0.025" will be plenty.

In other news ...... both the piston and jug are stamped with the letter "C." I believe that refers to a diameter tolerance ? ? ?


The piston skirt has 0.21" clearance on either side of the exhaust port.


0.28" clearance on either side of the intake port.


That's as far as I got tonight.

Stihl Crazy said:

What you got in mind?

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I'll have to get it out of the trailer and see what I actually did to it. Tomorrow I'll drag it out. The kitchen table is covered with the 254 parts and empty beer cans as we speak. lol
Gypo

Couldn't resist posting a pic of the 980's big bro, the infamous 999.
Gypo

Tell me about the 999. Is it built on the same bottom end as the 980, or is it bigger and beefier ? How do you like the 999 ?

mtngun said:

Tell me about the 999. Is it built on the same bottom end as the 980, or is it bigger and beefier ? How do you like the 999 ?

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MT, the 999 is a virtual tank and is basicly a cutoff saw powerhead. It's 100.1 cc. I sold it to 4paws, but wished I still had it.
Gypo

Here's the jug, piston and carb off of it.
Gypo