Here is a write up I did some time ago - a little obsolete now as it does not include strato saws:
This is what I've learned about the older plastic Poulan saws – by older I mean pre-strato engines. There are similar Craftsman versions of many of these, which sometimes have slightly different mix of features.
Poulan Wild Thing
Models include the 1950, 2050, 2055, 2150, 2175, 2375, PP210, PP262 in displacements from 33cc to 42cc. There is no anti-vibe and they can be identified by the primer bulb and the distinctive vertical duct bulge that runs from the top of the recoil cover into the top cover. They're not that light and fairly wide, but not too bad either.
The engine is a basic clamshell type with a slug piston and open single transfers. The connecting rod is a flat cross section (stamped?), but is fairly thick and I've not heard of this being a weakness. Flywheels have deep fins and they appear to move a lot of air.
Some have chain brakes, some don't. Clutches are outboard type with simple spur drive sprockets. All use 3/8 LoPro chain. Most use Walbro WT carbs and foam air filter that works OK if it's oiled. The plastic clutch cover/chain brake tend to warp a bit over time, especially with heat from the clutch area, as they are supported only at the bar studs. Bar studs are toggle head bolts and go though the plastic case (as opposed to being threaded into the plastic like an MS250).
Poulan 2250
Models include the 2250, 2550, 2555, PP220, PP230, PP260, in displacements from 36cc to 42cc. These are the same basic design as the Wild Thing family, but have A/V. The A/V uses a spring-type suspension for isolation, which tends to be rather soft and allows a fair amount of movement, but it is smooth. There are considerable differences in the choke and throttle linkages, on/off switch, the carb, the top cover and the air filter mount. The top cover on these has two internal ridges that help keep the air filter seated, which the Wild Thing ones do not have. The choke is located on a terrible position and is really hard to access with gloves.
Chain brakes were optional. All use 3/8 LoPro chain.
Poulan 2500 (P600)
Models include the 2500, 2600, 2700, 2750, 2775, 3050, PP255, PP295, PP4620, PP310, PP315, as well as the Jonsered 2036 and 2040. Displacements run from 36cc to 49cc. There is no primer bulb, and the Jonsered versions have a different shaped recoil and top cover just for decoration. The engines in this family are different from those in the Wild Thing family saws. For one, the crank is about 1/2” narrower, and the flywheel has shallower fins, allowing the whole saw to be lighter and much narrower as well. They are about 10lbs.
The connecting rod has an I-beam cross section. They use a chromed bore. The exhaust port shape is very similar to the Wild Thing, but the intake is a bit different. These saws respond very well to opening up the muffler and make a surprising amount of power for their displacement. They use Walbro WT carbs and a flocked air filter.
There is an external handle frame with a spring-type suspension for isolation, which tends to be rather soft.
Some of these are labeled “Turbo” and some are “Super Clean” - the Turbo versions use the small scoop by the flywheel fan to keep debris out of the airbox, while the Super Clean ones just have a pickup in the air stream between the cylinder and the carb. Only the Super Clean type parts are available any more, but they mostly interchange – there are some differences between early and later saws regarding the intake boot and impulse line.
Chain brakes are on most later saws. Most of these use 0.325” chain.
I have found three design weaknesses on these saws. First, the muffler heat shield on earlier Type I saws fatigue fails in the area around the muffler outlet. If you have a chain brake it can melt when the deflector falls off, and heat damage around the muffler is common. Second, the engine mount screws often back out. There is no locking hardware and they sit in a floating shoulder bushing that can spin so it would not work well anyway. Locktite will not work well with the thread type on the original screws. Many saws have been damaged by lost or broken screws. Last, the A/V mounts are easily damaged if the saw gets pinched and a gorilla tries to yank it out.
Husqvarna 36 (P600)
Models include the 36, 136, 141, 142 in displacements from 36cc to 40cc. These use the same engine family as the Poulan 2500 series, but have a different “saddle” type case that fits over the handle/tank and has rubber A/V mounts. The A/V system allows less movement than the spring types used on the Poulans. The size and weight is about the same as the Poulan 2500 family. The air filter looks similar to the 2500 but is slightly different, and all use the Turbo filter scoop. Some of these are 0.325” and some are 3/8 LoPro chain, and the 142s came with 0.043” Microlite. Clutches, drive sprockets and bars interchange on all these saws.
The 142e saws come with catalyst mufflers that are very restrictive. With a little bit of work the muffler and heat shield can be replaced with the parts from the 141, which really helps power.
