Jetting 101.

[roostrocket]

good write up!!! im currently at 170 60 and stock needle and air screw and im def rich should i drop down to a 48 and move the needle to the 4th clip and turn the fuel screw a half turn? thanks and again great write up!!!

p.s. mods are in sig sealevel and 65 to 85 degree weather.

[SyKo450]

Get a better needle....

[roostrocket]

Get a better needle....[/b]

ive looked for a better needle is there anywhere that sells needles by them selves? all i have been able to find is whole kits.

[SyKo450]

I believe www.woodwardspecialties.com does

[jeffy1214]

great job i was gonna pay to have this done you saved me 75 bucks thank you!

[orangejuiced450]

So has anyone done a 07 that didnt have to take the carb out? I tried everything, but to get at the needle its gonna have to come out. whats the best way to do this? I know this is going to be a dumb question to most, but what is the black hose on the break side for? can it be disconected with no problems? any other tips or tricks for this job?
Thanks!
By the way, just changed out the main to a 165 from 155. now im bogging off idle. thats the only change so far.[/b]

i have a friend with an 06 that i have jetted b4. try taking the bolt out of the rear brake fluid reservoir and push the reservoir aside as u turn the carb . it works ive done it. the rear brake fluid resevoir was relocated in 06. try taking off the the throttle cable too if neccessary- behind cover on right side of the carb.

[aggressor]

Here s a quick question if any one knows. i have several Keihin jets from my 250R fourtrax, they look very similar to the ones on my 2004 YFZ450. Do they interchange? They look the same and are the same length. Help.

[Ted J]

Okay... This might sound like a very dumb question, but here it goes. If I want to put the clip in #5 postion am I placing the clip on the 5 th postion from the bottom of the needle or the 5 th postion from the top of the needle. I am thinking from the bottom to richen it (allowing more to pass). By the way I have a GYTR kit[/b]

Anybody got an answer for this, I'm curious about this too.

Also, the mixture screw, what where are they referencing these turns? From that of stock and if so, if somebody else has messed with it how to do I know how to get it back to the starting point?

Thanks!

[husker525]

Anybody got an answer for this, I'm curious about this too.

Also, the mixture screw, what where are they referencing these turns? From that of stock and if so, if somebody else has messed with it how to do I know how to get it back to the starting point?

Thanks![/b]

Clips are counted from the blunt or rounded end of the needle, which is the top of the needle. The lower the clip position, the richer the mixture.

As far as the mixture screw, the turns are referenced from gently screwing the screw in all the way to closed, or rightey tightey, then backing out left loosey a prescribed amount of turns. Before you start, count how many turns it takes to go to the closed position, then write this down. This is your baseline or factory setting.

[Captain Jack]

Here s a quick question if any one knows. i have several Keihin jets from my 250R fourtrax, they look very similar to the ones on my 2004 YFZ450. Do they interchange? They look the same and are the same length. Help.[/b]

Yes the Jets will interchange.

[Captain Jack]

ive looked for a better needle is there anywhere that sells needles by them selves? all i have been able to find is whole kits.[/b]

Call LRD Performance (Just Google LRDPerformance, not sure the rules on posting Links and Phone Numbers) and tell them to ship you a EMP needle and clip. After I expirimented with several diffrent jetting configurations I found that for me the NCQV needle was just to lean. It didnt ever perform crisp and seemed to be the cause of the infamaous bog.

See my post here for my jetting specs. Hope this helps.

http://www.yfzcentral.com/invision/index.p...st&p=623805

[Captain Jack]

ive looked for a better needle is there anywhere that sells needles by them selves? all i have been able to find is whole kits.[/b]

Call LRD Performance (Just Google LRDPerformance, not sure the rules on posting Links and Phone Numbers) and tell them to ship you a EMP needle and clip. After I experimented with several different jetting configurations I found that for me the NCVQ needle was just to lean. It didn't ever perform crisp and seemed to be the cause of the infamous bog.

See my post here for my jetting specs. Hope this helps.

http://www.yfzcentral.com/invision/index.p...st&p=623805

[NANNYYFZ450]

I am currently running a pro armor full system and modified air box. Im using a 175 main jet. And kept everything else stock but when i got to crack on the throttle real quick its wants to die out and kill itself. But if i make it thru it idles fine and picks up rpms fine. but just when you snap on it quick it wants to die and if u let off and slowly go through the rpms its ok. If u hold into it when it cuts out after snapping on it. it will die. if u could send me in the right direction i would appreciate it...........

[NANNYYFZ450]

still no hits on what it might be read my post right above

[frank mb]

In that picture where you see the main and pilot jet, there is another jet or screw, what kind of jet is that?

[choptop50]

NO race gas does nothing but blow out your pipe stock pistons don't compress enough to com bust the fuel. All you will do is spend more money on gas. the biggest thing I've found is to get the mixture screw set and make sure the bike is warmed up. it makes a big difference. Also There is a lot of people that worry about the bog if you stab the throttle there is no reason I can think of to do this. Am I the only one that works the clutch out at the same time? Get your r.p.m.'s up before you need to take off. If it's doing it while you driving that's a jetting problem most likely, then you can worry about a bog. Am I mostly right about this?

Thanks for this how to re-jet thread. Very helpful. Made the job alot easier. Great work!!!!

I have a new bone stock 2007 yfz450 (first Yamaha quad) with a very frustrating bog off idle. Most threads I have seen acknowledge this and say to re-jet and change to 4th clip position on the needle.

I could not rotate the carb enough to access it. Looks like its hitting something. I had to remove it from the engine. Not terrible but a little more involved. I also noticed that my 2007 needle is not adjustable. Only one clip position. I re-jetted the pilot and main (now at 45/16 but I am stumped on the needle. Some say to shim it, I am not familiar with shimming. Will a 2006 needle work in a 2007? Any help? The bog lessened with the re-jetting but still stumbles when stabbing the throttle just off idle. My next step is to figure out how to shim the needle and add a power now unit.

I want to make this bog go away completely on my 2007. Does race gas help. I am using pumped gas at 93 octane.[/b]

[choptop50]

Clips are counted from the blunt or rounded end of the needle, which is the top of the needle. The lower the clip position, the richer the mixture.

As far as the mixture screw, the turns are referenced from gently screwing the screw in all the way to closed, or rightey tightey, then backing out left loosey a prescribed amount of turns. Before you start, count how many turns it takes to go to the closed position, then write this down. This is your baseline or factory setting.[/b]

The Works connection(thanks for the sponsor) mix screw I used said to turn the screw in until it engages then pull gentley down until it comes loose of the threads. that is you start point. turn it in 8-11 times mine was exactly 8. The mix screw i used is markd 1.2.3.4 so it helped to do this.Back it out 1'1/2 turns and leave it. Don't turn it in to much you dont want to bend it. Now with everything back together you can blip the throttle and turn 1/4 at a time in or out until you are happy.if it needs more than two or three turns out you need to tyr new jetting same with in if its in all the way I beleive its the pilot you need to change. hope that helps.

[ancona2]

hey can someone help me with the bog problem i have when i stab the throttle. i don't want to make another thread so i'm asking on this one. my mods are in my sig and i ride mostly at glamis/ sea level, 60-70 degrees. i've tried just about jetting combo and i'm currently at, 48 pilot 205 main ncvq on 4th clip #40 leak and 2 turns out on the a/f screw. is it too rich or too lean off idle??? thanks

[NANNYYFZ450]

the reason i want to know on hitting the throttle real quick is because when i come out of a turn on my track. XC it is. there is a lil creek like deal that u wanna pop your front end up and over and i wanna just be able to crack it and pull the front end up. I know that its something its not me and its not just then when it does. it. its also when im gettin on the throtte a littl slower. so thats prolly y people wanna know about it on snapping the throttle.

[dole12688]

I have an 07 yfz450 stock right now but will be putting a two bros slip-on, K&N with precharger, and running the air box cover on on the trails and off on the track and drag strip so I really want it set up for being off Im guessing any way if anyone could tell me the main and pilot I need to run and what position I need to have the yz needle at and the fuel mixture turns I live in Victoria Texas which is around sea level I think and is 80-100 degrees F in the summer and for winter which is 50-70 F here so what do I need in both conditions I know how do the jetting just need to know what to put in it thanks for your help guys in advance