What's the best piston to swap into a Jonsered 490 closed port cylinder?

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Stratostreak

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I've done some reading on this subject...Lots of real good info on this site, but am unsure of what piston to buy. I cannot find a OEM Jonsered 490 piston and am considering buying a Stihl 028 piston and re-cutting the dome to lower the compression if needed. Has anyone found a good interchangeable replacement piston for the Closed port 44mm Jonsered 490 cylinder? If modifications were needed, please share. Thanks in advance.
 
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I've done some reading on this subject...Lots of real good info on this site, but am unsure of what piston to buy. I cannot find a OEM Jonsered 490 piston and am considering buying a Stihl 028 piston and re-cutting the dome to lower the compression if needed. Has anyone found a good interchangeable replacement piston for the Closed port 46mm Jonsered 490 cylinder? If modifications were needed, please share. Thanks in advance.

Unless something has been changed earlier, a 490 should have the 44mm top end of the P5000, and not a 46mm one. The 46mm closed port one was used on the P5500 and PP325, no Jonsered model. :confused:
 
I am about to invest considerable time into answering this very question but, as of right now, Ebay is your best bet. Just a few minutes ago I bought a 490 carcass off Ebay for $60 shipped that includes a good top end. I just had a NOS 45mm closed port top end delivered today, another Ebay find, and I hope to be able to find replacement piston options for it as well.

How about the piston from a Husqvarna 350? I have measured them up and they seem to be a direct fit to the 44 mm Partners.
The 44mm Husqvarna 350/351 piston should fit but the 490 piston is windowed and the 350 is not. I am not 100% sure just how that will effect the running but I am sure Jonsered had the windows for some reason.
 
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I am about to invest considerable time into answering this very question but, as of right now, Ebay is your best bet. Just a few minutes ago I bought a 490 carcass off Ebay for $60 shipped that includes a good top end. I just had a NOS 45mm closed port top end delivered today, another Ebay find, and I hope to be able to find replacement piston options for it as well.

I pondered that carcass too... and too long, now it's headed your way Roanoker494...now I'm leaning toward a new Meteor Stihl 028 piston...then turning a new dome if needed, to lower the compression (I'd like this to be a long running & strong little work saw, but not too hot).

Any thoughts on this question: Would a non-windowed piston like the Husqvarna 350 piston compromise the potential of the cylinder porting, especially in the cut?

I guess that's one of the reasons I'm leaning toward the Stihl 028 piston...it looks like they're windowed.....I was just hoping that someone else had already ruled out all of the inferior options by trying them already.
 
I pondered that carcass too... and too long, now it's headed your way Roanoker494...now I'm leaning toward a new Meteor Stihl 028 piston...then turning a new dome if needed, to lower the compression (I'd like this to be a long running & strong little work saw, but not too hot).

Any thoughts on this question: Would a non-windowed piston like the Husqvarna 350 piston compromise the potential of the cylinder porting, especially in the cut?

I guess that's one of the reasons I'm leaning toward the Stihl 028 piston...it looks like they're windowed.....I was just hoping that someone else had already ruled out all of the inferior options by trying them already.

I am currently running a 028 piston in one of my 5000 saws, it works fine but it did have a bit too much compression without a gasket but after reinstalling the base gasket it has only 200 lb comp now and runs every bit as good as the original piston did. To install one you will need to remove metal from between the pin bosses to allow the wider Partner rod to fit in between the bosses, the Stihl rod is narrower. Its easy to remove just enough metal from each side to get the partner rod to fit in.
 
The 028 could be a possibility, there are many variables that need to be addressed. First off is the piston pin diameter, your OEM 490 piston will have a 10mm pin. Length of the piston skirts, the piston is useless if the skirt comes above the bottom of the exhaust port. Pin to crown height, too much and it will hit the top of the cylinder and too little it will hit the crank or you will end up with weak compression. Most all of these issue could be overcome but machine work don't come cheap.

Don't drag your feet on a 490 top end for less than $100 while I am around, I snatch em all up........ I bought one 490 just to use the top end on a Husqvarna 50 Special build and then parted the rest out. In the end I made my entire investment back, still have a few parts laying around and got a "free" top end out of the deal.
 
I am currently running a 028 piston in one of my 5000 saws, it works fine but it did have a bit too much compression without a gasket but after reinstalling the base gasket it has only 200 lb comp now and runs every bit as good as the original piston did. To install one you will need to remove metal from between the pin bosses to allow the wider Partner rod to fit in between the bosses, the Stihl rod is narrower. Its easy to remove just enough metal from each side to get the partner rod to fit in.

Thanks for that info, guess I need to stock up on a couple 028 pistons

BTW
Looks like we must have been typing at the same time.
 
:dizzy::laugh: PP325 46mm pistons can still be bought new :msp_rolleyes: 5000 windowed 44mm pistons can not be bought new. So which is really harder to find. :msp_wink:

Art had good luck with the 246 piston in 5000. Again open the bosses.
 
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I have been pondering this also and am not sure of the best way to go yet.

I have a 028 piston here and really don't like the looks of it that well as the skirts are very narrow and it appears they barely cover the ports. That dome don't come close to matching the combustion chamber either so flame travel would have to suffer.

I picked up a AM 350 Husky piston with the thought of cutting Windows in it but I'm not sure if this particular brand is best for that either. Really haven't had time to do all the research needed to say for sure yet.
 
:dizzy::laugh: PP325 46mm pistons can still be bought new :msp_rolleyes: 5000 windowed 44mm pistons can not be bought new. So which is really harder to find. :msp_wink:

Art had good luck with the 246 piston in 5000. Again open the bosses.
Hi all,

Well I’ve got also a 490 closed port cylinder but piston needs replacement..

Unfortunately i can find only chin 490 piston in Greece / Europe..

But I’m thinking of purchasing a 246xp windowed Meteor piston..

Any feedback on this combo??

Many thanks
 
Hi all,

Well I’ve got also a 490 closed port cylinder but piston needs replacement..

Unfortunately i can find only chin 490 piston in Greece / Europe..

But I’m thinking of purchasing a 246xp windowed Meteor piston..

Any feedback on this combo??

Many thanks
This thread 10 years old. :oops:

Here is info of a 490 5000 built using 246 piston. Info on Page 6 with pics and video. http://chainsawrepair.createaforum.com/partner/partner-5000-plus/
 
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