Big old Jonsereds...

Cut4fun · January 07, 2011, 08:29:37 PM

The 630 thin rings can still be found too. ;)

I'll put my ole stock 65cc Poulan against a stock Jonsered 630.

weimedog · January 08, 2011, 09:50:48 AM

So the 920 project begins...have the two test mule saws, a Jonsered 820 and Jonsered 920 both stock to start with. I'm going to up grade the 820 with a cylinder cut to match the case window's...and intake widened slightly and lowered a small amount along with the transfers & exhaust cleaned out. Only change to stock timing is lowering the intake a bit...then we can run them back to back to see if those mods helped or hurt! (Actually a better plan is to run it with Spikes really clean 930...where those cylinders came windowed from the factory I believe. AND his is a very nice and clean sample of that model that also has other improvements such as the intake filter & filter horn)

Stock

roughed out...

weimedog · January 08, 2011, 04:30:58 PM

To thin or thick ring sould I go?

Have an Episan thick ring after market piston and two thin ring OEM used but good Jonsered pistons....I'm leaning towards the Episan...anyone have good things to say about those thin ring pistons?

Al_Smith · January 08, 2011, 04:35:54 PM

Less ring drag .FWIW about all newer model auto engine use skinny rings .Also why some people only run one ring in a cookie cutter .

weimedog · January 08, 2011, 07:53:51 PM

Sort of wish I had a better camera so you all could see the quality of the episan vs. stock...I have to say the aftermarket slug is pretty well made!

HolmenTree · January 08, 2011, 08:57:20 PM

My older brother raced his Jonsered 80 back in the 1970s with sucess against much larger saws,along with pulling the base gasket he also pulled the bottom ring and ran just the top ring. She was a real screamer.

Willard.

SawTroll · January 10, 2011, 08:08:14 AM

Quote from: weimedog on January 08, 2011, 04:30:58 PM
To thin or thick ring sould I go?

Have an Episan thick ring after market piston and two thin ring OEM used but good Jonsered pistons....I'm leaning towards the Episan...anyone have good things to say about those thin ring pistons?

.....

Just a thought - why not use the thin ring ones as long as they last?

weimedog · January 10, 2011, 09:09:46 AM

Quote from: SawTroll on January 10, 2011, 08:08:14 AM
Quote from: weimedog on January 08, 2011, 04:30:58 PM
To thin or thick ring sould I go?

Have an Episan thick ring after market piston and two thin ring OEM used but good Jonsered pistons....I'm leaning towards the Episan...anyone have good things to say about those thin ring pistons?

.....

Just a thought - why not use the thin ring ones as long as they last?

Nothing like common sense....actually might as well! Other wise those perfectly good pistons will just sit on a shelf as I continue to rationalize my way into after market stuff!

HolmenTree · January 10, 2011, 12:19:18 PM

Weimedog when you remove material from the cylinder's base spigot you are increasing crankcase volume which hurts performance gains.
You will have to stuff your crankcase with enough material to compensate what you took off the spigot.

Willard.

weimedog · January 11, 2011, 12:15:22 PM

Thanks for the heads up! :P...There is a bit of history here as well. The 930 J-reds came with a cut outs at the cylinder base and everything else being about the same (except intake horn & filter) had a significant power gain. So two things that will be tested here is:

1) replicating the change the 930's had on the 930 cylinders..does that add power? (Actually I basically matched the windows on the cases where the 930's were just milled straight (they stuck an end mill in and made a short linear cut..that's it)..I'll post the pics again)
2) Three other mods are in play. Increase intake duration, slight increased in compression, and increased x-sectional area of the exhaust, and slight mods to the intake track.

Then I will test side by side...if I went backwards...oh well...

(I will degree it at some point...just starting this one.)

So pic repeat & compare:

The cylinder on the left is the one I hacked at, the one on the right is the stock 930 cylinder.

After the hacking:

What isn't shown is the widened & enlarged exhaust & widened & lowered intake. If it doesn't gain..I toss the cylinder and do something else! Have two more...the experimental one has a chuck out of the top fin and its the guinea pig..if things work..I have a nice cylinder I will replicate the mods to...If I gain nothing..I'll build it back to stock and be happy!

weimedog · January 13, 2011, 08:24:55 AM

Two pics..First is the 820 right after tear down. I had stuck it together this time last year with a "Golf" brand piston...just for kicks more than anything else. Never heard great things but never heard any bad things either about those after market pistons..so I bought one and put it in. It ran for the summer as my big saw. Ripped a lot of pine lengths for barn timber and blocked the larger timber for firewood. More use than a "Home owner" would give a saw, less that if I had used it as a primary saw (that honor moved from 455, 351, to 365 Hybrid this year) ; much less use than a pro. But two things are quite clear. First is how clean the Bel-Ray H1R burns (Almost no ash) and the entire inside had this "blue" film of oil..REALLY nice to see! This is typical for my stuff. Has been for 25-30 years since I learned how to deal with synthetics. The second is that golf brand aftermarket is perfectly happy in there. I had posted about this at another place, I had to file a "chamfer" on the inside of the skirts so it would clear the crank halves! The casting is much thicker than stock in the piston skirts. Also what isn't seen is on the top ring, at the gap, it was pretty dark on the top ring. No marks on the cylinder but wonder if that end gap was a bit big...didn't measure as the focus is on building the 920....

Golf Piston after a year of farm service:

Typical job for the 820 this last year:

The next is the difference between the 920 cylinder going on, and the 820 comming off!
920 on the left:

weimedog · January 13, 2011, 08:50:54 AM

Also going to first try one of those "thin" ring OEM pistons before running the episan. AND I found out you HAVE to run a base gasket with the stock piston as there is a slight interference in the combustion chamber. Looks like when they final bored this cylinder during manufacturing, they didn't get all the way to the top on the intake side and there is this .010 - .015 step right before the combustion chamber that interferes with the top of the piston. Tempted to take the other "OEM" thin ring piston I have and cut a .015 x .020 clearance chamfer around the top edge & take out the base gasket. Might be a candidate for a "pop up" as well.

weimedog · January 13, 2011, 10:14:31 AM

Reassembled the modded 920 cylinder on the 820....ready to test:

NEXT Big Jred Project: Have to fix cover or get different one & helicoil bolt holes for the cover. Also need an on/off switch...details details. This one is a late model 80 (serieal No. 491015) with a 90 top end....but this will be AFTER a little Husqvarna project..

Spike60 · January 14, 2011, 07:31:19 AM

What color top came with that saw? Silver or black? Rather than an 80, I think it might be an 801. 80's had the cylindrical style air filter that was used on the 621. I probably have an extra black top cover. The silver covers I have a for 621's, which are a bit narrower and don't fit. But since you've got the 801/90 air filter set up, you have to go the black route. But, as you know, I have a few cans of silver paint.............

weimedog · January 14, 2011, 08:50:05 AM

Definitely the black top version with the ignition related stuff attached to the cover.

BTW fired up the "820 to 920 project saw" last night..and it runs well....need to put it in some wood to see if the initial impressions are carried into something real. It has much better throttle response and revs higher no load vs. the stock one I put together a couple of weeks ago...side by side.

weimedog · March 28, 2011, 11:45:09 AM

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 · March 28, 2011, 12:25:40 PM

The Finished 920 with some plastic & cosmetic upgrades:

weimedog · March 28, 2011, 12:29:23 PM

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 · March 28, 2011, 12:34:34 PM

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 · March 30, 2011, 01:40:25 AM

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

weimedog · March 30, 2011, 07:45:55 AM

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 · March 30, 2011, 08:13:05 AM

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. · March 30, 2011, 12:53:51 PM

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 · March 30, 2011, 12:57:35 PM

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

weimedog · March 30, 2011, 01:46:00 PM

Quote from: Saw Dr. on March 30, 2011, 12:53:51 PM
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.