Chainsaws

Nate,

You did not say what model year is your Model 455, or If its fairly new?

Next, sometimes looking at a fuel filter its difficult to determine its condition, they sometimes get varnished over and may just be a little yellow or brownish, and Not the pristine white color when new, the best check is just replace the fuel filter, that is usually the number one problem.

Next check that all the fuel lines are good, no cracks or not fitting properly fuel lines, a loose fitting fuel line will suck half air and half fuel, and the engine will not run properly at full throttle. Also check for any fuel leakage or puddling in the carb. compartment this usually means something is not tight on a fuel line.

Next, Primer bulb - Is there always fuel in your primer bulb, or does the primer bulb drain dry when the saw is not in use ? or drain immediately after pumping it up ? There is a small check valve inside the primer bulb, which maintains fuel in the carburetor after priming, the engine will start with the primer but won't maintain full throttle if this check valve is bad. How easily is the primer bulb pumping  up the fuel ? If in doubt replace the primer bulb.

Finally, since you didn't say how old the chainsaw was, and the only thing left is the carburetor, you could have a metering and/or fuel pump diaphram problem inside the carburetor. You will need a carburetor re-build kit, and take the carburetor apart and replace the diaphrams and gaskets. Oh also when taking the carburetor apart thoroughly clean all the jets both low side and high side, verify that the real fine fuel inlet screen inside the carburetor is clean too, this will give the same symptoms as a dirty fuel filter if you have a partially plugged fuel inlet screen.

I hope this helps - A can of spray carburetor cleaner works real well to clean out the inside of the carburetor.

PS. - I am Not a Husqvarna Representative or a Authorized Repair, just a experimental chainsaw person.