Between Partner 500/5000, Jred 490/590, Poulan 325 I have over 20 of these saws. (my favorite smaller saw)
The Partner 5000 closed port is the identical to the Jred 490. The 590 is better in my opinion... same compression (my running 590 has almost 200lbs) same port timing, the 590 is 45mm and the 5000+ is 44mm. Many people
think a Husky 55 45mm closed port is the same as a 590. It is not, they use the same mold, but the Husky's have different timing numbers and a larger combustion chamber. They are still good, just not as hot as a true 590 top.
In my opinion the 325 Poulan/Partner 5500 is king of these style saws. At 46mm and basically the same timing numbers, they rock.
ModifiedMark is the only person I know with a 5500 Partner. :drool: