Please Help Identify Old Jonsered

Swine · September 29, 2021, 10:50:33 PM

Hi all, bit of a lurker and newbie here. A have an older Jonsered that was passed down to me from my grandfather. I grew up logging and splitting wood with him, and after he died the saw sat around for a number of years until my grandmother passed away. It has a lot of sentimental value: about 7 years ago my stepfather passed it on to me after having it "tuned up." I've always had issues keeping chain tension and I'm wondering if the person who worked on it may have done something wrong or installed the wrong bar (thickness or proprietary design or something?). It's become exponentially worse this fall and I can't really use the saw for more than a few cuts before the chain tension makes it completely unusable.

In trying to track down parts I can't even seem to find what model number it is. Can anyone help? I have attached a few photos of the saw and the bar (Oregon). The serial number appears to be 1983 – 22733 (it might be hard to see, I can't seem to get Google to give me any matches with it...)

Any help would be appreciated. I am mechanical (I do 90% of the maintenance on our trucks, tractor, and motorcycle), but haven't really worked on saws much – so I'm just looking for some guidance as to whether I can rectify the situation or I just need to go buy something new at this point.

Thanks!

SnoJetter · September 30, 2021, 08:32:09 AM

Looks like a 520SP.

Likely not many will agree with me, but personally, I love that family of saw. I've got one 520 and a few more of the 455 & 535. I've used them on a regular basis for over 20 years and they've never failed to fill the truck with firewood. Like you, my grandfather was a significant influence exposing me to logging at an early age.

Most parts are no longer available, but there is an increasing number of used parts on ebay. Not sure how I feel about that as it appears there are many sellers dismantling saws to sell as parts - but that's their prerogative. I've collected a dozen or more parts saws myself that will either be donors or projects as time permits.

There's nothing magical about the bar or chain design or tensioner for that matter. Are you holding the bar tip up when you tension the chain and tighten the bar nuts? If not, when you are cutting, the bar will "slip" into that "up" position (due to the clearance in the bar slot with the studs) and you'll lose tension right away.

Otherwise, leave the chain cover off and take a look at how much slot is left in the bar once you've got the chain close to tensioned. Perhaps the chain is a link too long and has stretched over time. Your bar is stamped with a 66, so your chain should have 66 drive links - count 'em. Might be as simple as getting a new chain and maybe a new bar to go with it. I suppose the tensioner threads could be stripped. Maybe there's enough bite to tension the chain, but not enough to hold tension while in use.

Swine · September 30, 2021, 10:41:14 AM

Thanks so much SnoJetter.

So the chain does have 66 teeth; however, I must confess, I haven't been vigilant about lifting the bar tip when adjusting tension. I hope that it's just been my silly user error.

I do have a couple other questions if you have the time. My understanding is that when a bar is worn there is lateral play in the chain, and if there is so much that I can hold a straightedge on the side of the bar and the chain is pushed all the way over, then the bar is worn out. Is this correct?

Finally, there is a lot of movement on the driveshaft (my word) of the chain sprocket behind the clutch. Probably between 1/8" and 1/4" inch. Is this normal?

Apologies, I just have no reference for this. My granddad was many things – a scholar and a skilled carpenter, but mechanical knowledge (in retrospect) was never where his aptitude lay so I'm just learning as I get back into everything. I am relying on the wood burning stove more and more every year and it dipped to 26 degrees last night so I have some work to do ;D

sawguy21 · September 30, 2021, 11:33:22 AM

I think it is a little newer than a 520SP, possibly a 525 but whatever. The chain will lose tension as it heats up and stretches when used but should return to normal when cooled off. Is it getting adequate oil? Check by bringing the saw up to 1/3-1/2 throttle while over a clean light colored surface, you should see a dark streak coming off the bar tip. The play in the crankshaft bearing is not good, that is often caused by overtightening the chain. If the seal doesn't hold the idle will be erratic, at worst the piston will overheat and destroy itself.

SnoJetter · September 30, 2021, 01:29:58 PM

I don't think you are referring to end play of the crankshaft itself. If I'm reading it correctly, my guess is you are talking about the ability to move the chain sprocket laterally on the clutch drum. This saw has an outboard clutch and likely a rim drive. Yes, it is very normal for the rim sprocket to have that 1/8" or so of movement on the splines. It isn't uncommon to miss the sprocket when installing the chain and lay it alongside the sprocket due to that freeplay. I've done it a few times myself!

As far as the procedure on checking wear of the bar, I can't comment on that. Rather than wear the bar channel out, I've had worn rails, heavy burring, and nose sprocket failures that have resulted in replacement. It's difficult to read the chain width dimension on your bar, but it looks like it's .050, though it could be .058. I bet a guy could run an .050 chain on an .058 bar without trouble, though if the channel was severely worn, a narrow chain might cause trouble. You'll need a chain expert to answer that one definitively, though.

Swine · September 30, 2021, 03:18:24 PM

Thanks all!

Yes, SnoJetter, you are correct. The crankshaft itself has no movement, I can pull the clutch up about 1/8" (no wiggle or slop on the crankshaft) and then the chain sprocket and washer behind does have the ability for movement and what I would call "slop" perpendicular to the crankshaft (photo below – you can see that I have pulled up on the left side and the chain sprocket/washer are canted).

Sounds like this is normal though. The bar is an .050 and I don't have any burring and the nose sprocket spins nice and smooth so it seems like as long as the chain sprocket movement is normal I should chalk this up to user error on my end when adjusting chain tension. However, I do need to take a closer look at the chain tensioner threads, my coffee hadn't kicked in yet and I forgot to give that a good look.

edit to add: As I was typing this I thought to myself, there is so much side to side movement of that chain, I should measure the drive lug. It's less than 1mm! On the .050 bar it should be 1.3 mm. I think whoever tuned it up put the wrong gauge chain on it; could that be causing it in some way to have too much movement and work itself loose? I hope something didn't get ruined with the few cords of wood I've gone through in the last couple years with that chain. But as you said, if someone can run a .050 chain on a .058 I guess I don't know why that would be an issue...

I think step one must be to get a new chain ASAP.

I really appreciate the insight and help. I'll update as I trouble shoot!

Tacotodd · September 30, 2021, 03:40:35 PM

You do need a new drive sprocket because that one is worn beyond the wear limiter marks. Just look at Oregon drive sprockets and you'll see what I mean. Anytime that you can no longer clearly and easily see the lines on them, that's your clue for replacement time.

Swine · September 30, 2021, 07:10:13 PM

Well, yet another thing I wasn't aware of. Thanks Tacotodd! Totally makes sense now after looking at pics of new sprockets. Looks like I'll be tracking some items down in hopes of getting work done this weekend.

sablatnic · September 30, 2021, 09:50:21 PM

All the above is correct, it should be a 520 SP, the 525 was next years model.
Don't worry about your present chain, it can't be too narrow, the .050 bar is the narrowest for that pitch. .050" is 1.27 mm so your measurement is correct.
Good luck with it, it is an interesting saw. That large washer behind the clutch can make some funny sounds, so don't worry if you hear weird yells and screams.

firefighter ontheside · September 30, 2021, 10:08:53 PM

To make sure the bar is tipped up while tightening the nuts, hold the saw with your left hand on the back handle, rest the bar nose on a piece of wood(that will keep the tip up) and tighten nuts with right hand.

Swine · October 01, 2021, 04:37:02 PM

Well, I have good news and bad news to report. The good, I believe I finally figured out why it wouldn't hold tension: the tension bolt was bent and as a result over time as the chain loosened when I turned the bolt it would move the retaining pin (or whatever it is called) AWAY from the slot in the bar, and because the pin was already worn down there was literally nothing holding the bar in place. Photo below –

The bad news. I removed the drive sprocket to take to the store to try and find a match. I read about the old remove the spark plug and put a nylon rope in the cylinder trick. You can probably guess what happened next: I reassembled everything and the rope was stuck, I tried to work the crankshaft back and forth and thought I had it and then, the rope broke off.

So... I guess my next question is, how hard is this case to split? Is it even worth it at this point? If so, anything peculiar about taking this thing apart that I should be aware of?

I guess my disappointment is tempered by the fact that I've been lusting for a new saw, but it still is disappointing nonetheless.

Tacotodd · October 01, 2021, 05:20:00 PM

Pull the cylinder instead. You'd have to do it anyway to split the case. THEN the rope is going to be easy to remove. You might try other tricks but I can't think of what they might be.

sawguy21 · October 01, 2021, 06:33:02 PM

That is a clamshell design, the crankcase splits horizontally and crankshaft and piston come out the bottom as a unit. It means tearing the saw down which you may not want to take on by yourself.

lxskllr · October 01, 2021, 06:51:17 PM

Maybe try taking the muffler off, and see if you can get the rope through the exhaust port.

Swine · October 01, 2021, 08:18:29 PM

Well, I tried to pull the cylinder but looks like someone got to it first, one of the hex bolt heads was totally stripped. So that's a no go. I'll take a look through the exhaust port in the morning, I got a bit more rope out but it's still catching something bad at the top of the stroke. I can't see anything, no idea what the catch is.

Quote from: sawguy21 on October 01, 2021, 06:33:02 PM
That is a clamshell design, the crankcase splits horizontally and crankshaft and piston come out the bottom as a unit. It means tearing the saw down which you may not want to take on by yourself.

I'm not super savvy on small engines – haven't had one apart since high school which was more than half a lifetime ago, this means I could leave the head on when I split, yeah?

At this point who knows what other stripped bolts or other things are wrong so I'm inclined to just tear it all apart if not for nothing else but to learn. Definitely leaning hard towards picking up a new Husky in the morning though too ;D I'm not excited to spend the coin but I probably wouldn't regret it long term.

beenthere · October 01, 2021, 08:36:59 PM

For recovering the rope, try a fish hook on a fish line leader and poke around to see if you can get a catch.

sablatnic · October 01, 2021, 09:56:06 PM

You should be able to drill the head off the bolt with a 5mm / 7/32 drill, and pull the cylinder. When the cylinder is off you should be able unscrewing the headless bolt with a channel lock. I am afraid though that the piston is damaged by cutting the string, but it is worth a try.

Real1shepherd · October 01, 2021, 10:46:40 PM

This is why I use a small, cut V-belt for a piston stop. In over 40+ yrs, never had a problem and it always stops the piston without damage. I was never onboard with stuffing a floppy piece of rope in there.

I think I usually cut a stretched out TroyBilt tiller belt....I recycle most things.

Sorry, can't advise you on clamshell designs....never had one.

Kevin

lxskllr · October 01, 2021, 11:03:38 PM

That Vbelt's a good idea. I don't quite trust rope, and I've read of broken cylinders using a piston stop. As luck would have it, I just dug up an old belt I don't have another use for, so now I do.

Swine · October 03, 2021, 01:18:08 AM

Vbelt is a great idea. I also thought about one of those black rubber bungee cords without the hooks. Sadly, that was my first rodeo and apparently something went wrong. Part of the rope must have worked itself past the piston... Maybe.

Anyway, I'm going to turn it into a weekend project, breaking the whole saw apart to figure out what happened. It's actually a great learning experience.

I went out and bought a 545 Mark II this morning. I can't complain, it's amazing how much I got done today. Saws have made some pretty significant gains in the last 38 years😁

I really appreciate all the help. I'll keep updating as I tear this thing apart. Hopefully others find my journey helpful.

Real1shepherd · October 03, 2021, 11:44:15 AM

I'm guessing the rope slipped into a transfer port and got hung up....you'll see it with everything apart.:D

Kevin

SnoJetter · October 04, 2021, 11:25:53 AM

Tearing these saws apart is a snap. They are a little quirky in design as compared to the newer stuff, but disassembly and reassembly are not difficult. Just take your time and maybe take a few pictures as you move along in the process. I've had these saws stripped down to give them a good cleaning and total time for the whole process is less than an hour.

I've had a few "stripped" cylinder bolt heads, and drilling out the head until it separates from the screw body is very effective. If you have access to a drill press, that makes the job much easier with a true vertical drill angle.

This saw will have a thin base gasket (is a much thicker, harder base "gasket" on the 455/535) that can tear. If that happens, there is NOS on ebay for $10. I've used Yamabond with no gasket on occasion and it works fine.

Don't rule out the possibility of getting the cord unstuck by just removing the muffler. Work the flywheel back and forth if there's any play and you might get things loosened up enough where you don't have to tear the whole thing down.

Enjoy!