2006 yzf450 main jet

15 replies to this topic
  • Gcarey

Posted May 04, 2006 - 09:51 AM


Is anyone going back to the stock main jet for temperatures above 70 deg around sea level?

  • Ga426owner

Posted May 04, 2006 - 12:11 PM


Not me at 900ft :crazy:

  • yami racer

Posted May 04, 2006 - 12:17 PM


I am riding tonight in 80 degrees for the first time with the 48/170 and I will see how it is...I may go 45/165 depending on how tonight goes. I will let you know.

  • Gcarey

Posted May 04, 2006 - 12:17 PM



I want to re-jet for the warmer weather and would like to be as close as possible because the carb is such a pain to get at!

I was thinking of trying a 45 pilot and richining up the needle one clip but wasn't sure about the main jet.

Anyone with any other suggestions for above 70 and around sea level?

  • motobark

Posted May 04, 2006 - 09:39 PM


I was running 48/170 until last weekend. I had been thinking it was a little rich before, but when I put on a Vortex ignition the jetting was definitely too rich. I went back to 45/165 and it runs much better. The over-rev was a little higher and sharper and the 1/8 to 1/4 throttle acceleration was better. I think going to a 48 pilot to stop the backfiring is hurting off idle acceleration. A little backfiring is ok.

Another clue is with the 48 pilot it barely needs the choke when cold and it won't hesitate at all immediately after starting dead cold. All I know is my bike is running better with the 45/165 than it did on 48/170. I'm not sure if it was the Vortex or the slightly higher temps, I just don't have that many hours on this bike yet to tell. This was at 700 to 2000 feet and about 70 degree temps. The humidity was probably pretty high too which would have also made it a little richer.

I'll be riding at a little higher altitudes (from 2000 to 4500 feet) this weekend so I'll see how it does.

  • Wheel

Posted May 04, 2006 - 11:28 PM


What is so difficult about changing jets in these carbs? The main and pilot are both accessable by removing the plug in the float bowl, and the needle is accessable by removing the fuel tank. The carb never even has to be loosened.

  • l8r

Posted May 05, 2006 - 03:05 AM


I totally agree with the 45/165 jetting. I also have moved the needle up/clip down to 5. I am also using a Boyesen QuickShot with with a 50 leak jet. The throttle response is super crisp. I had a 48 pilot in at one point, but it was a bit rich after the bike warmed up. When going back to the 45 pilot, I noticed more low end power/throttle response than the 48. Oh yeah, the fuel screw is ~ 2.125/.250 turns out using the Tusk fuel screw from Rockymountainmx.com. It is a nice part with an oring on the shaft to keep tension on the screw so it will never fall out! The temp has been ranging from 70 to 90 degrees at about ~600 feet above sea level.

  • yami racer

Posted May 05, 2006 - 05:14 AM


I ran the bike lat night and agree it was rich with the 48/170..I am going to go 45/165 and try that this weekend.

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  • Gcarey

Posted May 08, 2006 - 10:15 AM


I ran the 165 / 65 combo this weekend with the clip position on 5 and the bike was much more responsive. On decel there was a small amount of popping but I think this is normal.

  • Ga426owner

Posted May 08, 2006 - 10:42 AM


I ran the 165 / 65 combo this weekend with the clip position on 5 and the bike was much more responsive. On decel there was a small amount of popping but I think this is normal.

I assume you mean 165/45???

  • Gcarey

Posted May 09, 2006 - 04:15 AM


yes that's what I ment. I have to type fast so the boss doesn't catch me. :crazy:

  • KTMKarl

Posted May 09, 2006 - 09:05 AM


I'm all the way back to stock at 900 foot and temps hovering in the 70's and low 80's with high humidity, actually had to crank the fuel screw in a 1/4 turn from stock over the weekend.

  • black_n_blue_thumper

Posted May 09, 2006 - 10:11 PM


I'm at 165/45 at 3000ft. Runs great. :crazy:

  • l8r

Posted May 17, 2006 - 03:53 PM


Did you try to turn the fuel screw out to eliminate the popping? Just rode last night and it was cooler, 70ish and very dry, experienced some popping, but 1/4 turn out on the fuel screw fixed it.

  • Ga426owner

Posted May 18, 2006 - 05:37 AM


I heard yesterday some owners are going to a 50 pilot jet at sea level...man that seems steep to me.

Has anyone tried the different leak jets on a 06?

  • KTMKarl

Posted May 18, 2006 - 09:29 AM


My personal opinion is that a lot of folks are using the old Butt-o-meter to swap brass and the fat settings seem to hook up better and thus give the impression of more torque. I'm all the way back to stock, raced in 55-60 degree temps sunday 900 foot up off the sea level and once she had been running 5 minutes or so to get some heat in the motor she was great, when the engine is cool i have some back popping and a little too much throttle response! she will get a little snappy till the motor is warmed up. after that its perfect. Most of our races are sub 20 mph woods runs and i was haveing trouble with the bike loading up with the richer settings even when it was cool outside I didn't have the 48 pilot screwed in the carb for more than a few hours before going back to the 45 and now to the stock 42. Same with the main but it isn't as noticable unless i am at the MX track.

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