06 yz450f jetting start point


7 replies to this topic
  • TREBOR0323

Posted August 25, 2010 - 11:49 AM

#1

Looking to get a smoth throttle delivery from off throttle to full throttle and as little popping as possible,bumped up the stock 06 yz450 pilot to a 45 still has got the 165 main with the clip on the needle in the third slot from the bottom.i ride at sea level to about 3000 feet.fuel screw out 2 turns.so my question is am i close with this combo or do i need to up the main jet also?

  • sacfelix

Posted August 25, 2010 - 12:00 PM

#2

I live at sea level as well and run a 45p in the summer and a 48p in the winter, a 165 main jet, stock needle in the 4th position and every thing else is stock. I have great throttle response and no popping. I did have to play with the A.P pump timing though to get it right. I am at 1 3/4 out on the fuel screw. I tried a 168 & 170 mj but the 165 made the bike respond alot better especially under a load. I just happen to notice that you posted this under the WR section. Is it a WR or YZ?

  • TREBOR0323

Posted August 25, 2010 - 12:09 PM

#3

Its a yz,my bad i'm a newbee,thank's for the input

  • William1

Posted August 25, 2010 - 02:28 PM

#4

You have a race bike, not a play bike. If you try to 'jet away the pops' the bike will not performas well as it was designed to. Your bike does not have a coast valve like the WR's do. You are supposed to be on the gas or on the brakes, not coasting. If you richen the bpilot enough to make the popping go away, you will have a very had time hot starting it. You should select the pilot and set the fuel screw for a perfect idle then leave them alone. If the popping is a biig issue, get a WR muffler and carb.


Pilot jet and fuel screw are for idle
Needle straight diameter is for just off idle to about 1/4 throttle
Needle length/taper and clip position are for 1/4 throttle to just below WOT
Main jet is for WOT

You must adjust by testing and not arbitrairy guessing. You should attack each segment individually then do the next in the following order
Pilot-fuel screw
Main jet
Straight diameter
Taper/length/clip

For a good starting point, take a read of the YZ jetting database. Find a bike like yours, same air density and modifications. Use the consensus you find as a starting point.

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  • grayracer513

Posted August 25, 2010 - 02:53 PM

#5

Looking to get a smoth throttle delivery from off throttle to full throttle and as little popping as possible,bumped up the stock 06 yz450 pilot to a 45 still has got the 165 main with the clip on the needle in the third slot from the bottom.i ride at sea level to about 3000 feet.fuel screw out 2 turns.so my question is am i close with this combo or do i need to up the main jet also?

My set up for an '06 operated in SoCal between -80 to 3700 feet is 165/45 stock needle (NFPR) with the clip in #4. I use this from April or May through November or December. Between December and May, I run a 168 main to adjust for the temperature. I'd say your needle was too high, but I haven't run your bike.

Some bit of popping on decel is a sign of the idle circuit being setup right in a YZ450. Excessive popping can be caused by exhaust leaks, and you should always check that first before adjusting jetting to correct it.

Also, look here:

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and here:

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and also, here:

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  • ttr250dude

Posted August 25, 2010 - 07:45 PM

#6

Main jet affects 1/2 throttle to WOT but mainly affects 3/4 to WOT. Yamaha says so.

  • TREBOR0323

Posted August 26, 2010 - 05:58 AM

#7

Well,thank's for all the help.i 'm going to the thr oregon coast range this weekend the elevation is about 1200 to 3000 feet.i'll use the 45 pilot set the clip in the number 4 slot on the needle and adjust fuel screw after i get the bike warmed up,let you all know how it turns out

  • TREBOR0323

Posted August 30, 2010 - 07:36 AM

#8

Well after riding this weekend looks like the bike is dialed in,runs great not much popping pulls real hard, fouth gear wheelies,yee ha.start,s easy but needs hot start when it gets hot,1 to 2 kick,s. I,m real happy with this bike i picked it up for $2,000.i,ve checked valve's(all spot on)tire's are like new,fork seals not leaking,spokes nice and tight,quick shot acc pump,r&d fuel screw,custom white graphic,s the origanal yellow and black anniversary plastic,s(like new)very little boot wear on side case.with regular maintenance i hope it holds up.anyway thank's to all the tt members that help weekend rider mechanics like me.





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