I have a husqvarna 575xp which i bought used.It was running great for 3 weeks when the motor started to race, the stop switch didn't seem to work in this state so i had to use the choke to shut it down. I thought it might had been the air filter so i blew it out and started it with the same problem. Could someone point me in the right direction.

seems as the PSI based switch maybe having issues inside the pump most likely

Check the fuel line. The ethanol gas may have dried out the fuel line enough to have it crack. Many times the gas line brakes at the very end where it connects to the in-tank filter

Check your muffler spark arrestor.

Not turning off sounds like an ignition switch problem. Not starting - then I think you should check the Low Tension side of the solenoid again to make sure there is current from the switch. If the solenoid's OK, the battery's fully charged with all the connections clean and tight, then it has to be the starter motor or engine. Check you can turn the engine by hand, if so then I would guess, it's probably the starter motor.
Good Luck

husqvarna lth 130 with kohler 13 hp": have fuze any on it

Hi
Yeah,your switch has gone bad,and using the choke isn't how you want to kill it for too long.Fouled Plugs.Here's a link to the service manual pdf if you want to do it yourself. Shouldn't be too hard.
Please rate my post?
Bob
http://www.airtimeproducts.com.au/assets/docs/Husqvarna%20service%20Manual.pdf

The H jet needle controls full speed operation and L controls idle operation. Turn both screws CW to stops (lightly), then back out each CCW 1-1/2 turns. This should allow the engine to start and run. Make sure the fuel filter, air cleaner, and muffler are not plugged. Check the fuel lines for decay or damage. Make sure the carburetor fasteners are tight including the hardware that holds the carburetor to the cylinder. Start the engine and allow to warm up, then pull the throttle full on. Turn H needle CW until the engine starts to speed up--proper setting is when the engine 4-strokes unloaded, but immediately 2-strokes when cutting. Allow the engine to idle and adjust L CW so that the engine runs fairly well, but allows the engine to 'follow the throttle'. Adjust idle speed screw so that the chain stops turning, but the engine continues to run. Hope this helps!

check timing and valve adjustmen.

you are wanting a wiring harness

your best bet aside from ordering one is to buy a service manual from www.ferracci.com or local husqvarna dealer and use the wiring schematic to build your own race harness........don't forget the kill switch.

IPL for a 2009-04 pn 537 25 41-02 575XP (complete) here:
HusqvarnaUSA.com
http://www.husqvarna.com/us/homeowner/support/download-manuals/

Bailey's P&C only $351.28 + shipping
http://www.baileysonline.com/itemdetail.asp?item=537+25+41+02&catID=383
HTH
Lou