Big old Jonsereds...

[weimedog]

Update. The "slightly modded" 920 is now a mature functional saw. Its also a very strong saw. I've got several hours on it and it starts reasonably easily for what it is, runs cool, doesn't vibrate out of your hands,  nice brown plug,  doesn't leak gas or much bar oil, oils nice, chain brake NOW is on and works....etc. SO it's now in farm service.

The 80/90 isn't as happy a story. I tore it down and found a few tough problems to solve...any ideas appreciated.

1) Inside the tank the paint is disintegrating. (Had this on a 70E) as well) So it has been sucked into the fuel filter, fuel line, and ultimately clogged the screen filter in the carb..the saw apparently went lean and had a partial seize hence it came to me for repairs! THAT wasn't bad. I pulled the cylinder and scuffed up the piston & cylinder and put things back together. (Rings were fine) the compression went way up and things were looking even better becasue it had a nice hot blue spark! Could work around the paint in tank thing for a show saw.

2) In the process of putting things together, I discovered a little play in the ignition side crank bearing or so it appears. About a full .010 in. BUT when I started looking and my stock of parts, it looks like almost all the spare 80 / 90 cranks I have are corroded at the bearing contact point. That's three I have the same way. SO maybe that's what happens when they sit. Or maybe that's a weakness in the material selection on those saws. So I'm beginning to wonder if the play I feel isn't a bearing but actually the crank.

So...do we split the cases and see? Or just get it to run and don't run it often! (Pics will follow..I have a ton but it takes time)

[weimedog]

The Finished 920 with some plastic & cosmetic upgrades:

[weimedog]

The 90 project snap shots...

First..looks clean! The...carb screen clog, the hurt piston, piston cleanup and then cylinder clean up! (Can't show bad bearing or crank issue yet)

[weimedog]

One thing that strikes me as interesting is LOOK at those transfers! That cylinder is where we eventually got to with the 920 after bringing it to 930 specs plus or minus a little! Bet those Jonsered 90's were very strong saws! Wonder what the bore & stroke are vs. the 920. The intake is also cleaner than a 920 and more rugged in that it doesn't have that anti vib system inspired rubber boot that the 920 has. I think this saw or one like it might be fun to bring back to life...and maybe even mod a bit. Turns out in the spare parts bin I have a 80 bottom end, a 80 and a 90 piston....and maybe cylinders. The covers will have to trickle in over time I guess...

90 Cylinder Stock:


Modded 920 Cylinder:

[simplicityguy92]

do those 920s cut good im looking at buying a couple

[weimedog]

If you are going to build a business or start your career, I wouldn't choose them for a variety of reasons. Big heavy old saws. the standard 920's cut "OK" about like a 385 only a lot heavier. More torque than top end power.  Parts are hard to find. Bar mount is an odd size..(10mm). Weight. OK power for that weight..in their day, but not in today's world.

Having said that, For a guy like me they are perfect. With the 930 cylinder they cut very well, more like the 89cc class saw they are even in today's world. Still heavy for commercial use. If one of those saws is a "backup" with things like the ignition and intake boot, pull start, and chain brake in good condition, you could use them to earn a modern pro saw to put food on the table.

As a Jonsered collector of sorts, I love mine because I was able to mod them to modern levels of power and tweak and tune them to be a real functional big saw for my farm. That's my recreation, but I have a pile of saws as backup should I need work done in the mean time. I've got lots of parts saws to keep them going with as well. (Not going to part with any of it though) The attraction for me is they are a bit of an anomaly, easy to work on, they are Jonsereds, and mine are in fact fully capable of cutting with any modern pro saw of that size (90cc class saws)...maybe not weight yet but they are still evolving.

So it depends on what your plans for them are. But my first impression based on your stated age and presentation is no. Find a current "in production" saw like a 385XP or MS660.

[weimedog]

BTW I guess I never really did say much about how the 920 project saw came out other than it was functional. I did get the chance to run in public after a few hours of work/tweaking/tuning, brought it down to Spike's a few weeks ago, first blocking some oak, and then quartering (noodling) those blocks ...where it did a fine job. In fact its an animal power wise! I was very surprised at how much was gained by the mild porting (effectively grinding the stock 920 cylinder to a 930 configuration) vs. the stock 920..night and day! THEN yet again at another mini GTG where a modded 385XP decided to pick a fight with my 920....figured it would be close..but it wasn't. The 920 had both the power to allow me to lean its SEMI CHISEL chain and chain speed to run thru the test log faster head to head than that modded 385XP..(Actually that's not really fair, the 385 ran like a crazy thing but so does the modded 920..with a few more cc's) Either way it's an impressive for an old saw in its current form.

Photo Sumary of mods:
Cylinder with transfers ground to 930 configuration more or less (windowed to match the case windows):


Muffler Mod actually inherited from the 820 I started with and my typical mod, muffler was split, all internal baffles removed, a 3/4 tube inserted at the corner by the chain brake, and all brazed back together again. A pic of it "in process" roughed out.


SO My suggestion is instead of replicating this "cosmetically challenged" (ugly) transformation..find a 930s! Then you will have all the good stuff this one does plus it would be pretty as well!

Now back to the 90 ....more to come as we decide its fate ro to switch over to the 80 mystery saw...

[Saw Dr.]

Hey Walt, I have a 920 apart now (has been forever.)  Would you suggest I drop the transfers into the case on mine as well?  Did you do any other port work?  Was yours an NOS or Episan piston?  I have two pistons, but they're both pretty loose in the cylinder I have.

[simplicityguy92]

with alot of tork they seem like they would be a not bad rippings saw for log breakdown

[weimedog]

Hey Walt, I have a 920 apart now (has been forever.)  Would you suggest I drop the transfers into the case on mine as well?  Did you do any other port work?  Was yours an NOS or Episan piston?  I have two pistons, but they're both pretty loose in the cylinder I have.

Check your PM inbox...I would measure the pistons & inside of the cylinder to see which is worn. Hope its the pistons! Cutting the transfers to effectively copy what Jonsered in fact did with the 930 did help BTW. Episan's  are nice looking Pistons. I would have no problem using one..with OEM wrist pin clips.

[weimedog]

with alot of tork they seem like they would be a not bad rippings saw for log breakdown

Very true. I used my 820 for exactly that. (Then built it to a 920) The one thing that was a bit of an issue in my first built of the 820 was I used that soft yellow fuel line for the pulse line. That was a mistake! It melted & shut off the saw. SO back to that older style hard black line and it never melted again.

[HolmenTree]

Those older 'sered's came in different sized piston cylinder matchs "A" "B" "C"

Willard.

[Saw Dr.]

Along those lines, does anyone know if the Episan pistons are sized for the A, B, or C cylinders?  Pretty sure I have an A here.  (too lazy to go look right now...)