Some do not have cats, but are strato saws. I can give you advice for the strato variant below
Pulling one of the bolt sleeves out of the muffler on these is in essence a great muffler mod. Exhaust gas will flow pretty much straight out if you remove one or both. Removing just the one where the deflector is will make it appear stock in which the screen can still be used I believe.
The carbs usually need work. I’ve worked on two so far and both were very sluggish to respond and always seemed to allow fuel to pool in crank case. Pop off pressure if adjusted to around 14psi by removing coils in the spring, cured this issue.
Brand new out of the box I have found an air leak on the intake. I would suggest a full pressure/vac test on the unit to determine if you need to rip it apart and re-seal it.
Carb uses the standard ‘splined’ adjustment driver and do not have limiters. I’d recommend getting one much easier to tune with than modifying the splines to slotted and then using a flat head. Carbs are about 20$ on Amazon and very available.
Oiler works great and will support an 18” bar, non adjustable
They have an ok anti vibe setup. Same as regular huskys but for some reason vibration dampening is not nearly as good. Saw is as advertised in this respect, good for the firewood gathering and not any long term use if you value the feeling in your hands.
Extremely modular and easy to disassemble
Tough plastics make them long lasting machines, this along with the extremely non aggressive porting/sloppy tolerances makes them take a **** ton more abuse (lean conditions) than most.
Air filter is some what restricted. I drilled two half in holes straight through the starting instruction sticker on the back to help it breathe.
Uses husky small bar mount
These units use 3/8 lo pro spur gears, do not use regular 3/8 chain and bar. It will work for a bit but you will destroy your chain in time, the depth of the drivers are totally different between the two.
If you find a regular 3/8 spur gear clutch drum, let me know. As far as I can tell you are stuck with lo pro on these saws.
Poulan makes a 3/8 low pro 18” bar+chain for there other models it will fit.
Porting is limited, severely. You can open up the exhaust a little and trim the piston skirt to match the intake port at TDC but that’s it. I got one to run fairly well and was quite snappy, never did get to put an 18” on it though...
Thy are great learning saws, if you have the older non strato ones I would take the best parts from all and make one good saw.
Have fun, I sure did working on mine