I have a Husqvarna 55 chainsaw that has a crack in crank case

Tom, Check the attached links,instruction and guides on Husqvarna chainsaw, Good luck
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Husqvarna rancher 55 chain bolt replacement

http://www.husqvarna.com/ddoc/HUSO/HUSO2002_USen/HUSO2002_USen__1140106-95.pdf

How to Change Chain on Husqvarna Chainsaw Model 445

How to Adjust the Oiler on Husqvarna 55 Rancher

Is it possible that the crank shaft seized first and caused the pull rope to break?

not much point in doing so, engine is shot

I assume you're refering to cleaning the inside of the crankshaft and 'big end' to only way to access tis without splitting the crank case is to remove the cylinder head, to give you access to the crank shaft where you can flush it out with fuel.

The mixture is 40:1 that is 40 parts petrol to 1 part 2 stroke oil. Use good quality 2 stroke oil, e.g. Husqvarna or Stihl, rather than the cheap stuff you get at car service stations. This will prolong the life of your chainsaw.

55 IPLs start at page 4 but I doubt it has the level of detail you need.
HusqvarnaUSA.com
http://www.husqvarna.com/us/homeowner/support/download-manuals/
Enter the 3 digit model number (no XPs, Es, just the numbers)
Serial number decode – useful when downloading IPLs and Manuals
06 1500198
06 = year produced – 2006 (single digit before 2000)
15 = week produced - March
00198 = 198th unit Husky produced that week

I suggest you go here and join.
ArboristSite Chainsaw thread (free to join)
http://www.arboristsite.com/forumdisplay.php?f=9
The following thread is about your saw. Someone of will probably be willing to provide the photo you need. There are other threads where your saw is discussed.
http://www.arboristsite.com/showthread.php?t=122545&highlight=55+rancher
I must warn you. Many that frequent here develop an obsession with chainsaws. When I joined I had 1 and had only owned 2. I now own 7 and am always on the look out for a new one.
Good luck with your project. HTH
Lou

THE IMPULSE LINE FROM THE CARB TO THE CRANKCASE HAS POSS FAILED, CHECK THE FUEL LINES FOR CRACKS AND PINHOLES, MAKE SURE THE INLET SCREEN INSIDE THE CARB IS NOT BLOCKED, WORSE CASE CENARIO THE ENGINE HAS A BLOWN CRANK SEAL CAUSING THE ENGINE TO RUN VERY LEAN WHICH WILL IN TIME "COOK" THE SAWS RECIPROCATIONG PARTS. AS FOR THE SWITCH ISSUE THE SWITCH ITSELF IS PROB BAD OR THE WIRING HAS COME UNPLUGGED OR IS DAMAGED......GOOD LUCK!

there is a special tool to seperate the carnk case halfs.looks like a "c" clamp.they are very expensive to buy.there is no other way to seperate the case halfs with out distroying them......

It has a crack in the fuel line between the body and the tank. The crack lets air in the line. Replace the line.

Here's a link to the Husqvarna site that should be what you need:
http://weborder.husqvarna.com/order_static/doc/HOUS/HOUS2001/HOUS2001_1019194-95.pdf