Need Re-Jetting Help? ~YFZ450 Jetting Guide Inside~
This is a discussion on Need Re-Jetting Help? ~YFZ450 Jetting Guide Inside~ within the Yamaha YFZ450/450R (2004-Present) forums, part of the Performance /Technical category; yeah with you going as high as 8000 feet, the air is gonna get pretty thin....
I'm sure hoping it does!!!
I so can't wait for this snow to melt.....majority of my riding will be 4200 - 6000ft. As long as it is close enough to be able to adjust using the AF screw (when gaining altitude) and not have to re-jet in the field I'll be happy as hell.
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'06 YFZ 450, GYTR Jet Kit, GYTR Slip On, GYTR High Flow with Outerwear and lid removed, Handlebar Risers, 13T Sprocket, Al. Skidplate, O-Ring Mod, Throttle Spring Mod, Painted Headlight Surrounds
Went with the above settings and the thing runs like a raped ape! There may be a touch of fluctuation or hesitation in the mid-throttle area, but it was hard to tell for sure. I'm going to take it out to the dirt and open her up some more so I can get a better feel for how close to spot on it is.
Follow Up:
Well, a friend and I went out for a couple hours. It seems to be just about perfect. No popping, Backfiring, and the off idle hesitation is almost completely gone (I did the O-Ring mod today while I was in the carb). I can't cycle through all of the gears where we went because the trails are way too bumpy and it is hard to keep from getting thrown off. Time to get the suspension dialed in I suppose.
I get a lot of whistle from my airbox under the seat now...I'll just tell everyone it's my supercharger.
Thanks for everyone's help.
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'06 YFZ 450, GYTR Jet Kit, GYTR Slip On, GYTR High Flow with Outerwear and lid removed, Handlebar Risers, 13T Sprocket, Al. Skidplate, O-Ring Mod, Throttle Spring Mod, Painted Headlight Surrounds
I have a 2006 YFZ450 with a CP13.25:1 piston (110 oct+) 42.5mm carb, Fuel Customs Intake system, and an ESR full exhaust system (can is cut down to 9" <very short> with a vortex fin welded in the core to create a little back pressure)
Right now I'm running 45p, 180m, 1/2 turn on Mixxer screw, and 3rd clip on NQVC needle. I'm at sea level (or pretty close)
I just got it all back together, everything looks good (valves, etc) but it WILL NOT IDLE. I have to hold the throttle in (ever so slightly) to keep it running. Jetting issue or throttle cable issue?
How far did you turn the idle knob? and just to make sure, you did turn it clockwise correct? Going up a jet size is the last thing, have some one hold the throttle for you, and adjust the a/f screw out and see if it picks up the idle some, but usually unless you have the a/f bottomed out out, the idle knob will adjust it. Also, how much slack is in the thumb throttle? I usually adjust mine so that there is very little movement in the thumb.
I am taking on the challenge of entering a 1000mile desert race this August. My team and I are amateurs so we are learning about jetting. We have bought a brand new YFZ 450. How would you jet this bike to handle a 1000 mile race? The race is called Best in the Desert-Reno to Vegas.
I've got an 06 yfz450 I bought used. Came with a Dynojet kit installed.
Mods are K & N filter with no stock box and some thick metal piping from the filter to the carb (not sure if this is normal with the K & N or another add-on), stock pipe with sparky removed.
It spun a rod bearing and I just rebuilt it with a oe wr450f crank & piston and did the cam mod (retarded by one tooth).
I ride in MN in the summer - a bit less than 1500ft above sea level, fairly humid, and maybe avg. 80 degrees F.
On the first weekend after the build, I'm guessing it was running rich. It would not start without a small amount of throttle applied. With the choke out at all it would not idle - started, then sputtered and died. Trying to snap on the throttle (from say 1/4 to 3/4) when the engine was loaded down a bit (like up a hill) would cause some pretty hard bogging. The pipe didn't glow at all. And I don't think I can hit the rev limiter in 4th or 5th - but I'm not 100% sure what it sounds like when I do hit it (thought it should be obvious).
I kind of want to get rid of all the Dynojet stuff. Is that a really bad idea, changing it all at once? Or should I still do one thing at a time: pilot, then needle, then main?
Also, anyone wanna recommend a starting point if I swap it all out? I'm thinking 168 main, 45 pilot, 3rd clip on a NCVQ, and 2 turns out on the screw.
Lastly, in hopes of helping with the root cause of the accelerator pump bog I was thinking of dropping to a smaller leak jet. 70 was mentioned as popular earlier in this thread?
I would not recommend mixing Keihin with DynoJets, I would agree with the jets/needle you mentioned and do the zip tie mod and change the leak jet to a 35, I believe 70 is stock.
I would not recommend mixing Keihin with DynoJets, I would agree with the jets/needle you mentioned and do the zip tie mod and change the leak jet to a 35, I believe 70 is stock.
thx - I looked into that leak jet more and 35 is what I want, I think 40 is stock, though. I ended up ordering a bunch of sizes of mains and a few pilots so that I can take it all with me up north and figure it out over the long weekend. All together is was about $75, and that's way more than comes in any kit.
You bought way more than you will ever need. I normally ride between sea level and 1200 feet, but this weekend I went to almost 6000 feet and all i did was swap the main from a 175 to a 162 and rode it! I didn't even mess with the pilot, it still started up and idled fine. Unless you are racing, just get it close when going outside of your normal altitude, why waste your time jetting when you can be riding.
I am taking on the challenge of entering a 1000mile desert race this August. My team and I are amateurs so we are learning about jetting. We have bought a brand new YFZ 450. How would you jet this bike to handle a 1000 mile race? The race is called Best in the Desert-Reno to Vegas.
48 pilot
NCVQ needle on #4
165 or 168 main
Running a 180 is way to big on a stock motor even with a pipe and opened airbox.
If you really want to get it nailed dead on install the jet4power meter and buy yourself an Edelbrock carb. I run it on all of my quads and dirtbikes. Easy to adjust externally also. No need to tear the carb. apart and change jets because there are no jets.
I have hundreds of hours with the above combo and will never go back to a stock carb.
Sorry to make my first post a question ---- I have an 04yfz450 with a white bros e2 slip on -- cam mod -- and air box lid on. I am running 168 45 3 clips down on stock needle and 2.5 turns out. I have tried various combinations on jets / needle position / fuel screw and can not get rid of my backfire --- Flames!
#1 How do you know when it is a rich backfire verses a lean backfire when air is being sucked back into the pipe?
#2 Not many mods --- Jetting reccimendations?
I have read all jetting posts in yfzcentral / bluetraxx / here / and atv source and can not really find a true answer except for continue to play / thats why im posting -- I'm out of time and have a xc race soon (this topic)
Located in Southern Indiana sea level - 500ft Pops on decel---(makes me think lean) --- however pops on accel when in N from idle(somtimes under load) --- I have a bog but pretty sure leak jet needs to go to a 35 and the ac pump "mod" should fix that
turn the fuel screw out to 3.5 and see if it helps or hurts the decel pop. Ignore any popping when in neutral, the motor is unloaded and will act different than when it is loaded.
turn the fuel screw out to 3.5 and see if it helps or hurts the decel pop. Ignore any popping when in neutral, the motor is unloaded and will act different than when it is loaded.
3 turns out is normally the max. Further than that and you have a good chance of loosing the fuel srew.
turn the fuel screw out to 3.5 and see if it helps or hurts the decel pop. Ignore any popping when in neutral, the motor is unloaded and will act different than when it is loaded.
3 turns out is normally the max. Further than that and you have a good chance of loosing the fuel srew.
This was simply to test if the idle circuit was rich or lean and causing the motor to decel pop and anything beyond 3 turns means you need to bump up the pilot, but I have yet to see anyone loose a screw unless they pass 4 turns, and if you have an aftermarket screw, the loosing of the fuel screw is a thing of the past.
(this topic)
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