2005 CRF450R - New to me, weird jetting.

Guys, I feel like i've done all the research a noob like me can do and I still have a lot of questions. I'm not technically retarded, but some of you might think so after we go through all of this.


I purchased a used 2005 CRF450R. This is my 2nd bike (first is/was a 97 CR250).


First, the good stuff:

The guy I bought it from had the suspension tuned, skid plate, bark busters, desert tank, exhaust, etc etc. His plan was to race the Baja 500, but he never did it, so the bike sat for several years. First thing I did was tear it down and check everything I could figure out how to check. Valves are in spec, everything else looks great. Cleaned the carb and it fires up nicely, runs well enough, and feels like it has a lot of powerlb_icon1.png. But then again, I don't have another 450 to compare it to, so maybe it's running super weak - I couldn't tell you.


Now the Bad(?) stuff:

  • Stock jetting on the 450 is 165-Main 42-Pilot (as you all know) The jetting on my bike is 160-Main and 48-Pilot  (There's another jet in there that is labeled 72) I don't know what position the needle is in.
  • It was set up and ridden in California before I had it. I'm in Utah at 4500', temps vary a lot, but 50-80 F is probably average riding temps
  • This thing backfires like the 4th of July on deceleration.
  • The header heats up to glowing at night within 45 seconds of starting the bike.
  • The exhaust is aftermarket, and I don't know a thing about it.

All of this would lead me to believe that the bike is running super lean but I pulled the plug and it's black and sooty, not white at all.


Anyone want to pitch in and help me out with what is possibly wrong with this thing? Like I said, it feels like it has a lot of power, but I wouldn't really know any different.


Thanks in advance.






Pilot is too large. Put in a 42 and reset the fuel screw according to the proper procedure.


Backfires are normal with a open race pipe. However, repack it and check for leaks. Do not try to jet it away. Your bike is not made for coasting. Flat out or hard on the brakes.

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