Rebuilding the Jred 590

Ok... AS is like crack. One taste and you just can't put it down (or so I've heard).

I am preparing to rebuild my dad's Jred 590. He didn't show any interest in the project and didn't want to spend the minimal cash to get the P&C/ring/gasket..... "it was a great saw, but we don't make our living using saws, so why spend the money"....

So the way I'm looking at, its no longer my dads saw.

My purpose is two fold.

1. I want a second saw for firewood (oak, ironwood, hard maple, ash etc.). I'm not into comp's, nor do I think I'm heading in that direction any time soon.
2. A.S. Has put all these performance ideas in my head that I "can't" try on the 270 my wife bought me for Christmas since it would void the warranty.

As I begin the process I'll be taking lots of pics and asking lots of questions (most will be stupid ones..... sorry in advance). I've got a 490 P&C/ring/gasket coming.

Here comes the first set:

1. Last night I was reading about "squish". --> I want the saw to be as powerful as I can get it without sacrificing longevity. "Squish" (thinner base gasket) is a new concept to me.... makes sense for boosting compression.... what are the pitfalls? Will it wear out the saw faster?

2. The 490 head is closed ported (ok not that I know what that means anyhow).... I've heard you can get major gains by porting... I've got a few machinist friends that would likely do it for me for free. Should I attempt to port the saw before I put it together? Is that likely to lead to a saw that will burn up quicker? If so, besides doing the muffler, what else can I do to perk up the saw?

3. If I did decide to port the saw, am I likely to need a different carb? Currently its stock.

4. Will a muffler mod make much of a difference on a 1982 vintage saw.... the Epa wasn't as strict back then?

5. The break dosen't work, there's a Jred guy down the road with "a barn full of 490/590's with blown top ends". Should I attempt to fix the break myself, or being an important safety feature, is that something better left to a professional?

6. While I have it all ripped apart, what other performance/maintenance ideas do you have for me that I could do on a limited budget? Better to find out now than after its put back together........

Thanks,

Sugestions anyone....

LOL I guess the J red 590 isn't that popular.......

I'd love to do a bigger saw, but this one was priced right..... free.

This post only has 22 views in 4 hrs.

If you find something on rebuilding Partner 5000, or Husky 50/51, they are more or less the same saw - but there was a lot of different engines around, even when they had the same bore.

The 590 is a good saw. It may be tough to find parts for, but when you have her in top shape, she'll run right with the fastest 3 cube on today's market.

[QUOTE=Rowan;89463

1. Pitfalls include: More stress on starter rope, (might snap it if it's old).
2. Open up the muffler outlet, replace base gasket with sealer and raise the exhaust port the thickness of the gasket.
3. Nope.
4. Yep.
5. Depends
6. Improve intake flow.

Danger Dan said:

1. Pitfalls include: More stress on starter rope, (might snap it if it's old).
2. Open up the muffler outlet, replace base gasket with sealer and raise the exhaust port the thickness of the gasket.
3. Nope.
4. Yep.
5. Depends
6. Improve intake flow.

Click to expand...

I'm not trying to be mean, but...

most of that is very bad information to a guy that doesn't know a thing about saws or modifications. That is the problem with this place, a bunch of people running around that don't know what they are talking about, yet giving out information left and right. I'm not singleling you out, just try to refrain from giving bad or lack of information in the future.




Now, Rowman, I'll answer a couple of the questions in no particular order.

The squish is the space between the top of the piston and the ridge around the top of the cylinder. You'll need to measure the squish before trying to tighten it. The Jonered 490 and parter 5000 are identical twins. The base gasket is very thin on these models (.005-.010- If I remember right). Removing the base gasket will bump up static compression a little. If you have the clearance you will need a good sealer to replace the gasket. You aren't going to see a huge jump in compression on this saw (490) like you would others that had a thick gasket.

now, if you do remove the base gasket for more compression, without a little work on the ports, you are essentially retarding the exhaust port timing and advancing the intake timing. Most guys will raise the exhaust at least the thicknes of the gasket to get back to the stock exhaust, but because the intake is now opening earlier, other mods are sometime required. Raising the exhaust basically raises the powerband. I say basically because there are a lot of variables.

To one that isn't comfortable with it, I don't reccomend doing it yourself. Some people have and have had great results, and many more have made the saw run worse that it did to begin with (stock). I know I have screwed up my fair share of them.

The best bang for the buck to the newbie is a muffler mod and widening the intake and exhaust port.

I would not recommend the machinest deal, unless you know exactly where the the ports need to be, unless of coarse your machinst is a 2 stroke guru. The machinest would be good for machining the cylinder base down (for more compression, less squish). Ideal squish for a worksaw is about .020. All the rest of the port work is done with grinders, dremels, etc.

A closed port saw typically makes more power than a comparable open ported one in stock applications. Open or closed refers to the transfer ports.

I will try to get a pic of each to help show you the difference.

Removing the base gasket won't jeapordize the longevity on this saw (imo). Widening the ports too wide will. You go too crazy and make the port wider than the piston skirt, it is free ported and won't run worth a crap. There is also the chance of catching a ring on a super wide port.

A muffler mod will make the saw louder, but will make more power. The EPa might not have had a hand in it back in the 80's, but they still tried to keep them somewhat quiet.

I would start off with a fresh carb rebuilt before doing anything to the saw. Chances are it had old fuel varnish in it and was part of the reason it got burned up in the first place.



The brake assy is all located in the clutch/bar cover. You could swap all the parts over from a good one, or just get another cover if the guys indeed has the barn full of 490's.

Good luck, hope this helps you a little to get started. There is a lot of information out there, it just need to be found on the site. A lot of guys don't like to take the time to answer a bunch of questions.

Thank you for the responses

Great info.... THANK YOU!

Ok, so I don't think I'll port it.... my machinist friends are making automotive and medical equipment.... they're not into into boosting power in 2-strokes... Unless someone can give me some specs to go by... (Too bad Cut4fun cant post right now, I'm sure he's been through this)

Its got a new rope in it.... New carb kit, fuel line/filter....

I'm going to talk with the local guy again and see if I can get a couple parts donors from "the barn", anyone have any requests while I'm there.... from what he said earlier, I think he puts all the blown / "un-fixables" in the barn.... the farm part of the property was sold off decades ago.

Will definitely mod the muffler....

Hey Dan what did you mean by Improve intake flow????


Thanks again for your advice.

Rowan, Improving intake flow would include:
Widening intake port, as mentioned above.
Perhaps using a nylon mesh air filter instead of a flocked type.
Basically keep everything in balance. If you increase exhaust flow you should also increase intake flow.
Stang,
No offense taken. The intent of my post was to show interest in the thread. You did a better job of answering all the questions at one time. I would prefer to answer one at a time.
BTW, I'm currently putting a 490 P&C on a 50 Rancher.

Danger Dan said:

BTW, I'm currently putting a 490 P&C on a 50 Rancher.

Click to expand...

Cool, me too! It is not stock, and runs respectable. lol.

Got a 490 the other day that looks mint, need to play with that one too.


Really wasn't trying to be an azz, just like to see new guys get helpful answers instead of yeah, do this kind of thing.

Widen... semi rectangular, following the contours our the transfers but not approaching the width of the bore??

I'm thinking I'll get it running first, mod the muffler.. See how it performs and think about the ports afterward....

Once I've had it apart and back together once it shouldn't be a big deal to play after should I feel inclined.

Thanks again for all the advice... I think I'll start tearing it down tomorrow night. I'll post pics if I run into anything interesting.

Thanks again.

How do I remove this part?

So I've got the saw almost striped down, I'm cleaning as I go....

Prior to pulling off the old top end I want (need) to get the plastic piece that the carb mounts to the cylinder on taken off so I can clean up. I don't know the proper name, so Ive refered to it as the skirt. I've removed the bottom two bolts, I don't see any others, yet it still feels firmly attached??? The posts for the carb move (with the plastic skirt) independantly from the clyinder. The skirt appears to have cut outs for the fuel lines to pass.....


Am I missing something obvious? Shouldn't this just come off now?

PS I saw that crumb in the intake from pic 2 and have since removed it.

got it.

it was so dirty I couldn't see that it slid off in the direction of the intake transfer.

lol.... had to have a beer to figure it out.

a little more clean up and done for the night.

I got the old cylinder off. Looks grayish (lean on oil?) there are some petty good groves on the exhaust side, and the ring is welded into the piston. There's some pitting, bumps around the exhaust port.

Glad I have the other top end coming.

cheers

Side to side play in the conecting rod normal?

Another silly question...

Tonight I noticed there was some side to side play in the connecting rod.... I mean that it slides sideways on the bering attached to the crank.

Is this normal or a problem?

Rowan said:

Another silly question...

Tonight I noticed there was some side to side play in the connecting rod.... I mean that it slides sideways on the bering attached to the crank.

Is this normal or a problem?

Click to expand...

There will be some sliding laterally on the bearing. There needs to be some space there. However, if the rod leans left and right while the rod base does not move, you have some big end bearing wear. I had a 490 that I caught right before it failed. There were burrs on the bottom of the rod where the bearing was wearing into the rod.

Rowan said:

I got the old cylinder off. Looks grayish (lean on oil?) there are some petty good groves on the exhaust side, and the ring is welded into the piston. There's some pitting, bumps around the exhaust port.

Glad I have the other top end coming.

cheers

Click to expand...

Nice photos! So thats what a 590 looks like from the inside. That piston is scored up pretty good. The 490 has a windowed piston also, but it's a full circle design.

I wasn't really sure what you meantD Dan, so I snapped some more shots of everything.

For the muffler mod, should I try to push the bold posts through and discard the baffel, or just cut some holes?


One other thing....

I see one of the fuel tubes has a crimp in it, (you can see it in the other pics) is that going to be a problem?

Personally, I replace all my fuel lines when I rebuild a saw. Some may not need it, but I like to start totally fresh. Eliminates a source of trouble for a while, at least.

Bama

I had planned on doing all the plastic lines. But I'm talking about the brass (assumed, not sure if its brass) tube. In the post 02-04-2008 02:39 AM

the last pic, the tube on the left...

If I'm going to replace these, how do I go about it?

Forgot to mention, I talked to the local Jred guy today..... He said he has front handle, back handle, Break assembly, carbs, and various other items.... He said he know for sure he's got one complete parts saw in the barn and possilbly multiples.. I;m going to check it out tomorrow. I;ll check for the items that people asked me about in the PM's