535 replies to this topic

[Thumper Rog TT Member]

Will be going to a 55 Leak Jet, I posted a 90 previously. I am not sure why GYTR puts a 90 leak in the kit, maybe for those guys wanting to summit Everest. I assumed it was for a reason, maybe they over manufactured half million of them and just add them to each pack.

Also, all of the free mods were done, I didn't specifically say that.

Good riding.

[Thumper Rog TT Member]

Leak 55 installed, bike runs smooth and strong through the entire range from blip to wide open throttle. Front tire up on demand in first and second, third on the roll. About 78 deg today, low humidity.

Leaving it alone at this point, it's an absolute fun bike to pin in corners and ride in general.

[Toyo5spd TT Newbie]

Hey everyone,

I've posted on here before on jetting and the responses were awesome, so thank you. My next question for you all is this. I live in San Diego County CA. We ride in the 0-1000ft above sea level range but are taking a trip to SLC Utah and will be riding in the 5000-9000ft above sea level. The temp will be between 80-90 and very little to no humidity. We will be taking a 07 ttr-125, 01 yzf250 and a 01 KTM mxc 400. Any advice on the jetting for those bikes would be greatly appreciated.

Thanks

[Swede73 Out of work midget stuntman]

You may have to go down 1 size on the pilot or you may just be able to adjust your mixture screw.. Maybe a clip position too. I ride at sea level and cooler temps one day and then at 4000 at 90 degrees the next and I just adjust the mixture screw a bit and I'm fine.

Edited by Swede73, 09 June 2012 - 08:44 AM.

[Toyo5spd TT Newbie]

My only concern is that we are going  to be higher than 4000ft. We will be closer to 7-9000ft. and will the mixture screw be able to handle that or will i need to make a definite change to the jetting on those bikes. just trying to save money. I would like to do it myself, but not very familiar with that stuff on the bike yet.

Thanks Swede73, i appreciate all the help.

[Swede73 Out of work midget stuntman]

I just went riding at 8000 feet this last couple of days and had no problems. The little problems I did have we're so small it was not even worth changing out jets.

[debargew TT Newbie]

My setup as follows:


Model: 2012 WR 250F
Timing: YZ per grey wire mod but I have inserted a waterproof switch mounted inside the top of the airbox so I can switch back and forth between WR and YZ timing.
Main jet: 180
Leak Jet: 50
Pilot Jet: stock
Fuel screw (turns out): 2
Needle model/Clip position: JD Jetting Blue needle clip in position #3 (3rd position from top)
Airbox lid: Snorkel Still On, unmodified, I'm leary to do this mod  because I ride in a lot of wet, sloppy conditions.
Pipe: Stock with a PMB Exhaust insert
Altitude where you ride: 0-2000 ft (Virginia)
Temperature where you ride: 20 - 100F
Other mods: Gray Wire (switchable),  JD Jetting Kit, Throttle Stop cut to 20mm,  O-ring Mod on pump. Thinking about doing the AIS removal mod but unsure of the benefit with this.. bike is still new and I'm researching this.
Degree of satisfaction: Very satisfied. The JD Jetting Kit was a huge improvent compared to the other mods. I have the carb jetting set up very nicely on the first try due to seeing other setups in this forum. Bike runs great now. Thanks for sharing your setups guys.

Regards,

BD

Edited by debargew, 25 June 2012 - 04:47 PM.

[Riding4Racks TT Newbie]

I have played with my 2009 WR 250 F for a while now, and I have heard some guys talking about disconnecting their TPS... Not a good idea. To PROPERLY jet this thing, you must disable your acv and make sure that your tps is properly turned to put out spec ohm restistance. This is not a difficult thing to do, but without a properly tuned tps, you will never get the bike to run right at all throttle ranges....check your tps setting ! This can be done with the carb in the bike and the bike does NOT need to be running. If you have not already done this, try it...you will be amazed at the difference. All specs are in your book !
Also - re-enable your acv after you've got jetting right. The tps knows what is going on and is designed to work with the acv active, unless you like your bike running hot and cackling on decel...
1200 ft, 75-100 degrees, high humidity

09 WR 250F
All free mods
AIS removed
Airbox top removed
JD jet ,red needle,#4, 40 pilot, 80 main, boysen QS3 adj leak set at 50, fuel screw at 1 turn out
Fmf powebomb header,fmf Q4, 13:50 gearing for off road and tight woods,
tps set at 4.625 at Wide open (ohm) 0 at closed

Bike runs awesome, but I am sure I can get it better now that I know what the heck I am doing !

[nokickstandsallowed TT Gold Member]

Correction Update:

In my previous post #500, I mentioned that the air-box lid is "Off" - That is incorrect. It should read: "N/A"

My mistake by way of a copy and paste error - the highlight field went too far and re-highlighted the word "Off" when I was transferring the field header titles upon editing the post. I forgot to delete the word "Off" and replace it with "N/A" or non-applicable, because my bike is the YZ model.

The correct data is "N/A" - because from my past experiences, it is very difficult to remove something from a bike that you don't have in the first place, especially when someone tells you how; but you don't even know what model of bike you got when you asked for help-

The only thing that has changed, is the addition of a laser-etched numbered fuel screw. I actually broke down and bought one after five years - never really needed it; but hey, I haven't bought anything special for it in over a year - just the essentials. Or maybe I'm getting old   - It took me this long to correct something, or maybe I just don't visit the jetting base that often for our forum

Note to self:
Be careful when doing a multiple copy and paste procedure between three word editors and four open tabs for various websites NKSA!

[klink032 TT Newbie]

Putting a gytr oval slip on muffler on my stock 2006 yz250f and I don't want to pay to have it jetted nor di want to buy a whole kit, was hoping someone could tell me the new sizes I would need...  thanks

Model (YZ or WR 250F):   2006 yz250f
Timing (WR-YZ):   yz
Main jet:   stock
Pilot Jet: stock
Fuel screw (turns out): stock setting
Needle model/Clip position: stock setting
Airbox lid (on or off): off
Pipe: going from stock muffler to GYTR oval slip on muffler, header to rema
in stock

Altitude where you ride: 5,280'  denver colorado
Temperature where you ride: variable
Other mods:
Degree of satisfaction: stock setting has been good, sometimes low end bog

[RoostnRev TT Member]

Model (YZ or WR 250F): 2012 yz250f
Main jet: stock is (185) went to 188
Pilot Jet:stock
Fuel screw (turns out):2
Needle model/Clip position: needle is stock, clip is 1notch down from stock (which i think thats the 4th notch down from the top? can't quite remember all i know is i moved the clip down one notch from the stock setting because it was popping a little on decel)
Pipe:stock
Altitude where you ride: Upstate NY/Disctrict 34 I thinkk its ussually around 400ft above sea level

Degree of satisfaction: feels like a FI bike, can snap throttle fast as possible from idle or neutral to wide open and cant get the bike to stall, hiccup, or hesitate/bog at all, no bog on G-outs or hard landings switching the main jet to 188 made the power from bottom through the top range more clean,smooth, and broad/robust you could even here it in the note of the exhaust, sounds much more crisp/clean.This suprized me cause its summer here and its hot and humid which i thought ussually makes a bike run more rich as it is, correct me if im wrong? i think these bikes run a little lean off the floor, could be because they upped the size of the carb for 2012 from 37 to 39? not really quite sure but this seemed to eliminate any decel pop and bog if anybody else knows anything lemme know!

Edited by RoostnRev, 12 August 2012 - 01:02 PM.

[Vinsanity TT Member]

Model (YZ or WR 250F): 01wr250f
Timing (WR-YZ):yz,cam and ign(gray cut)
Main jet:160
Pilot Jet:42,72paj
Fuel screw (turns out):2.5
Needle model/Clip position:ocfkp,4th.clip
Airbox lid (on or off):off
Pipe:fmfpower bomb motocross/power core4
Altitude where you ride:9500-11500
Temperature where you ride:55-85
Humidity 10-50%
Other mods:QS1,tied AP,40leak,12/52 sprokets
Degree of satisfaction: still looking for more but good. High compression is next

What I have learned is that high altitude jetting is counter intuitive to tradiotional jetting. And by high altitude, I mean above 7500 feet. Air velocity through the carb at low speed develops less vacume on the fuel jets (Bernelli's principle) and therefore must be jetted RICHER. Larger than stock Pilot fuel jet( Smaller Pilot Air jet), Top end is traditional or leaner than stock. Especially with a mod exhaust ! And open box lid.  This means non OEM Jet Needles and air jets, and more AcceleratorPump!!!. AP is huge, Athena dual spray, Quick Shot, Small leak jet or QuickShot3 adjustable leak$$, Tied with O Ring or wire!! (Check Youtube FCR-MX Accelerator PUMP).....Advance Ignition timing!! WR's cut the gray wire, and move stator for advance.

As for needles, check the jetting charts out there/ vender sites. Hints:FCR-MX use N427..OB/OC(OB is chrome,OC is Brass) third letter is taper degree, larger taper(higher letter) is richer as throttle increaces..Fourth letter is where taper begins/straight diameter ends or length of staight..relates to clip position. The lower the letter,the higher on the needle the taper begins/the straight portion ends or the larger clip position(richer) for refrence. Fifth letter is straight portion diameter. Lower the letter the smaller the diameter and richer before the taper begins.

Bottom line, Rich on the bottom to 1/2 -3/4, for me 1/4- 3/4 then leane(160main)..... many tears to figure this out.... can't believe I never cooked my valves with how I always leaned toward lean....
Come back

[Vinsanity TT Member]

klink032... bet you need to tie the Accelerator pump and drop the leak jet to 50 or less for the low end bog, maybe a larger pilot jet and raise the needle. For the slip on, after market exhaust usualy breathes more and needs to be richer as well. Usually, not familiar with that specific product, but trial and error tends to be the way. Did you get extra jets with your bike? Refer to jetting charts noting throttle position  to decide what to change, and only change one thing at a time! I suggest JD Jetting kits !! to take the expence and frustration out of the equasion.
Ride on!

[Vinsanity TT Member]

Riding4Racks... How do you jet the pilot with the ACV out? It adds air to the pilot  when active( not under decell vacume) wr has #100 pilot air jet, yz with no acv has a #100

[Riding4Racks TT Newbie]

Quote

Riding4Racks... How do you jet the pilot with the ACV out? It adds air to the pilot  when active( not under decell vacume) wr has #100 pilot air jet, yz with no acv has a #100

It is my understanding that the wr and the yz do not have the same stock size PAJ.

Disabling the acv is only to check needle pos and main jet as to not pop or snap on opening or at wot....It will not show you anything about your pilot in my opinion because the only time it is activated is on high vaccum decel...the spring behind the diaphram holds is from cutting air, not neccessarily adding air at any time. It cuts half the air to the pilot circuit when the throttle is closed and the rev is on decel due to slowing by gear pull, this richens the pilot to keep you from burning up your valves on a long downhills.The bog is usually created by being too rich at the point when you crack the throttle open again to get up the next hill, this is where your ap timing and leak jet sizing come in effect. Popping on decel is not all that bad , but when all is good the wr will run cooler with the acv active on those long decels or downhills. This really creates a more enjoyable ride for you and those around you ! I absolutely hated the idea of the acv until I learned how to get the bike running right with it active, now I can see the benefits outweigh the frustrations of my distrusting the concept !   I actually started over from scratch today since our ride was cancelled due to weather. I ended up with a really sweet setup that I am sure contradicts every other setup on here, but the other setups I found on here did not work well for me at all throttle ranges, there was always a sacrifice somewhere throughout the range. Another variable that affects proper tuning is individual riding style, and that is difficult to express from one person to another on this forum. Here is what I came up with that had me out riding with a smile in the pouring rain today !

Stock PAJ-whatever it is i am not sure ( trying to only change one thing at a time this go round ! )
Pilot 45 with fuel screw at -1
Main 170
Needle  G-DEP R set at 4th pos
AP timed at .10 and O-ring wrap
BoysenQS3 set at -1.65 equivilent to 60 leak
Tps set at 4.625 wot and 0 closed
ACV active
Fmf powerbomb header,Q4 with spark arrestor installed
Elevation 1200 - Temp 68 - 100% humidity (Raining)

I think a lot of people have assumed that their acv was causing their bike to run poorly when it was probably actually the tps not being in spec--JMO so do

[Vinsanity TT Member]

Riding4Racks,
I mis-typed yz250f paj#100, wr250f paj #75.  Like your post !!! Have an older but basically same set up. So by disabling ACV do you mean pulling the spring out ? Confused as that richens the pilot circuit, as well as all other circuits a tad. If it works it works! Just want to make sure I understand your process.

[Riding4Racks TT Newbie]

Vinsanity, on 26 August 2012 - 01:18 PM, said:

Riding4Racks,
I mis-typed yz250f paj#100, wr250f paj #75.  Like your post !!! Have an older but basically same set up. So by disabling ACV do you mean pulling the spring out ? Confused as that richens the pilot circuit, as well as all other circuits a tad. If it works it works! Just want to make sure I understand your process.

To truly disable the acv, you must pull the spring and replace it with a thick washer of the same diameter to keep the diaphram from being sucked back which pulls the pin to cut the air flow, DO NOT FLIP the ACV diaphram or your acv will be cutting air at all times (without replacing the PAJ with a #100, flipping the diaphram will make you too fat at all times). To disable,simply replace the spring with a washer strong enough to hold diaphram in closed position...
Remember to put the spring back in to go test ride the bike or you will run hot, spit and sputter, and get pissed at me for telling you to put a washer in there...
Disabling is only for a stand test of throttle response and to listen for popping and snapping( on acceleration) if you may be too lean..I always aire on the side of rich for the safety of my engine and the well being of my brain and pocket book !
This ACV is complex and YES it does add air at times, but it works wonderfully for what it is intended to do if you are set up correctly.-Don't forget to set the tps after you make all adjustments and have the bike idling between 1800 and  2000 rp(throttle response may not be ideal just yet....tps MUST be in spec). Engine should be off while setting tps.
After you do all of this, you can make minor adjustments based on your riding style to your fuel mixture scew and your adjustable leak jet.
Too much emphasis is put towards changing out needles and mains....The AP timing, Leak Jet size, and Tps setting Run this system and allow you to set it perfectly to your riding style...take your time and only adjust ONE at a time....You will eventually find that you LOVE the bike that you have sworn at so many times ! --Good luck

[hworkmaniv TT Newbie]

[font=helvetica, arial, sans-serif]
Model (YZ or WR 250F): 2009 WR 250F
Timing (WR-YZ): Stock WR
Main jet: Stock
Pilot Jet: Stock
Fuel screw (turns out):JD 1.6 Turns out
Needle model/Clip position: Stock
Airbox lid (on or off): ON
Pipe: FMF Powercore Ti Slip-On
Altitude where you ride: 800-900Ft
Temperature where you ride:70-90 F
Other mods:Throttle Stop, JD Fuel Screw
Degree of satisfaction:[/font]
[font=helvetica, arial, sans-serif] Love it! Released so much bottom end and runs perfect now that I tuned it with the fuel screw[/font]

[nk_dimitrov TT Member]

Model (YZ or WR 250F): 2009 YZ 290F Athena
Timing (WR-YZ): Stock
Main jet: 168 (I tried 165 at first but with the 168 is better)
Pilot Jet: 42
AP: 60
Fuel screw (turns out):1.6 Turns out
Needle model/Clip position: NFLR/2nd but now due to colder weather will go to 3rd
Pipe: Stock
Altitude where you ride: 1400-1600m (4500-5500ft)
Temperature where you ride: 25-35C (77-95F)
Other mods: Athena 290, O-ring mode, BUD racing AP cover,
Degree of satisfaction: Bike has amazing throttle response, no bog. Pulls harder than i need. Need to tweak a little with the fuel screw.

Have fun!

Edited by nk_dimitrov, 10 September 2012 - 04:33 AM.

[06silverbullet TT Member]

i'm looking at rejetting my bike , it's an 06 yz250f. i ride a lot in barstow ca, just got back from the poker run today. anyways looking for some info on how to jet my bike for the area. currently it bogs like hell throttle response is terrible. thanks for the help in advance!

Edited by 06silverbullet, 14 October 2012 - 03:00 PM.