Husqvarna 455 low compression

I put a new prime bulb in and while I was at it I replaced the drive sprocket and clutch put in new air filter and spark plug. Now really low compression. Won’t start. What did I do wrong

Did you tighten the engine bolts in a star pattern. Try doing that after a teaspoon of motor oil into the spark plug hole. To help lube all moving parts. Then check your compression. Compression has to be 120 and up ok

I would suspect a faulty compression release.
A primer bulb, even missing, won't affect compression-Nor will clutch replacement (or lack of a clutch).
 
If you can post the full  model # so we can look up your specific model:
https://www.jackssmallengines.com/jacks-parts-lookup/manufacturer/husqvarna/chain-saw 
 
Looking thru the exhaust port (muffler removed) for any scoring will indicate 
the general condition of the internals.. Any decent scoring will (up and down on piston/ cylinder)
WILL lower compression..
.
IE, A Stihl MS201 with a scored piston / cylinder