I am going from memory here, but when I bought my 2007 WR450F, the prev owner had replaced the factory levers with ASR unbreakable levers and removed the clutch safety switch (part 5TJ-82917-02-00) and unplugged in from the harness (e.g. it was missing altogether). I did a bit more reading and searching and found that if you bought the part 5TJ-82917-02-00 and hooked it back into the harness but didnt bother hooking up to aftermarket clutch perch (or even the OEM perch), it would let the bike start in gear. In other words, when you hook it up to the original clutch perch and push it into place then only when you pull in the clutch lever it will allow you to start in gear....but, if you never push switch into the OEM perch (i.e. you have aftermarket perch), it will think you have the clutch lever pulled in all the time and you will be able to start in any gear including when you accidentally forget to pull in clutch while deciding to start in gear. I would much rather have that than looking for neutral when i killed the bike on the middle of a steep hill or the middle of a river.
I installed the missing switch into the wiring harness and then zip tied it under the headlight so it isn't flapping around.. I checked the parts schematic and the 2012 WR450F is using the exact same clutch perch switch as the '07-'11 models.
here you go:
Item 7 under the "Handle Switch Lever" schematic for the 2012 WR450F
Or, if you are comfortable, you can short out the wires as Krannie suggested above - the effect will be the same. I opted to take the approach that I did, so I could return to stock simply by getting oem perch and inserting switch.
Also, as someone pointed out above, sometimes there is enough drag on the clutch that sometimes starting the WR450F in gear can be problematic to get it to fire (apparently slows the starter just enough). I have definitely seen this phenomenon on my '07 and my buddies '09 WR450F. The "solution" when it doesnt spin starter fast enough in gear to fire is upgrade to a lithium battery with more cranking amps, or put it in neutral and use elec start, or just kickstart it.
Edited by SilvFx, July 19, 2016 - 01:45 PM.