Chainsaw Repair

Poulan 3450 3750 IPL  http://www.barrettsmallengine.com/partslist/poulan3450-3750chainsaw.pdf

Where are you leaking gas on old tank?  The tank vents are known for falling out. Inside top left between crankcase tank.

Straight forward replacement.  Just be careful pulling your carb not to tear old gasket between carb and flange. Slide off and reuse.

Inspect your impulse line, fuel line and intake boot for cracks etc.

First off...............your original leaking tank is probably just leaking at the vent.  The vent assembly on those consists of a sintered bronze 'filter plug' that fits into the side of the tank near the top, and a 'duckbill' check valve that's underneath that plug.  Best way to get the old plug out (if it hasn't fallen out on its own) is to drill a small hole in the center of it and pull it out with a self-tapping screw.  A replacement 530038264 plug is less than a dollar, and the 530026119 duckbill is around $3.  Both available through/from any Poulan/Husqvarna parts outlet..............including your local Husky dealer.

If the tank is actually leaking from somewhere other than the vent assembly or the fuel line and you DO have to replace it, then the only gasket you need is the carb mounting gasket 530069891.  Goes between the carburetor and the metal plate that seats against the flange end of the intake boot.  They're 'sandwiched together by two long studs. 

It's a bit tricky threading the two kill switch wires and the impulse hose (get a new hose while you're in there.............best thing to use is a length of BLACK Echo/Stihl/etc fuel line of the correct ID.......don't use Tygon) through the hole under the intake boot.  Be sure to take your time getting everything lined up right without punching/tearing a hole in the intake boot.

Don't tear the rubber AV buffers between the fuel tank and the crankcase either.  They have plastic expansion plugs that insert into them (with screws that thread into those to expand them).  You remove the screws, pry/pull out the plastic expansion plugs, and then reach into the rubber buffers with a hex wrench and unscrew the screws that attach them to the fuel tank.  If you're not careful the metal washers that are bonded to the rubber buffers will tear away......................and you'll need new buffers.  Mine were both shot when I got my PP330, so I ordered and installed new ones.

Edit:

Looks like Cut4Fun posted two more efficient, less wordy posts while I was typing.

Looks like Cut4Fun posted two more efficient, less wordy posts while I was typing.

But your post contains so much great info.   I'm just brief to get them on the right track.

Try seal all on a seam cracks  too.  http://eclecticproducts.com/sealall.htm

I have used it many times even on oil tank crack on plastic. Still holding.

I have found the best way to separate the tank and handle from the rest of the saw is to first.
Remove all covers including the starter assembly.
Remove the black plugs covering the antivibe.   Then remove all the screws in the antivibe holding the handle and tank to the main part of the saw where the cylinder sits.
Make sure to loosen the clamp that holds the rubber boot from carb onto the cylinder.
Take the handle bar off.
Take the wires loose for the stop switch so that they can be fished through when you separate the handle from the cylinder.
Take the Impulse line loose at the cylinder.
Install in reverse order.