Hoping someone with a lot more experience than myself might be able to help me out. Make: YZ450F 2012 model EFI Symptoms: idles for a minute or two and then stalls when hot and I back off the throttle it stalls after stalling when hot, takes lots of kicks to start again, when i remove the plug and dry and clean it the bike will start more easily What I had done to it before it started this: bike seized due to chain tensioner wore out and travelled up into the cam chain and head. replaced piston and cylinder (aftermarket Athena installed) assembled head with new valves and springs new cam chain set valve clearance replaced clutch (basket as well) After less than 10 hours, the stalling was happening too frequently to ride without losing my calm so I took it to the shop again. They spent seven hours trying to diagnose the fault with no results. reset cam timing and checked flywheel key found small amount of water in oil cleaned injector and air mixture screw checked crankshaft position sensor checked coil and cap replaced spark plugi inspected TPS, APS, atmospheric pressure sensor and kill switch It was getting too expensive to leave at the shop any longer so I am trying to have a crack at it myself. Does anyone have any ideas? I'm going to try to do a compression test or leak down test this week. Also, has anyone made up the test harnesses for this engine?... I'm not keen to buy a gytr tuner to test the sensors again if I can avoid it. Any help would be greatly appreciated.