Jetting FAQ's

[blaktopr]

Hey YFZdream, don't go that high yet. I have the same mods and also 15 tooth and heavy modded stock muffler. I have the 45 pilot and tried a 178 main and even though the bike pulled it seemed to have a little stumble. I would stay around a 172 main with the 45 pilot maybe a 170 with baffle in. If you are going on a trip, bring the jets. A 6mm and an 8mm socket. 9 and 10 will work also, just to have. You will need a wrench for the big plug under the bowl. A 1/4 drive socket a 6mm will get the main out. If the jet takes a long tube with it dont be afraid. Bring an adjustable wrench so you can separate the jet from the tube. the tube is 8mm, i think. Its best to put the tube back in first then the jet. that may be too hard. So put the new jet on the tube and put the assembly back in while holding the throttle open. This will keep the needle from getting jammed up. snug up the jet and put everything back. Before you do the jet change, race a buddy who is close to you, tie to 4 bikes win or lose. Then you can do the same after the jet change to see the difference. Stay in the range of 168 to 178 on the main, I think you will fall between those #'s. Oh, and have fun!!!!

[rude5321]

Please forward me a copy of jetting instructions---
thanks
rbsilva1@cox.net

[YFZdream450]

Originally posted by blaktopr@Oct 19 2003, 05:18 AM
Hey YFZdream, don't go that high yet.* I have the same mods and also 15 tooth and heavy modded stock muffler.* I have the 45 pilot and tried a 178 main and even though the bike pulled it seemed to have a little stumble.* I would stay around a 172 main with the 45 pilot maybe a 170 with baffle in.* If you are going on a trip, bring the jets.* A 6mm and an 8mm socket.* 9 and 10 will work also, just to have.* You will need a wrench for the big plug under the bowl.* A 1/4 drive socket a 6mm will get the main out.* If the jet takes a long tube with it dont be afraid.* Bring an adjustable wrench so you can separate the jet from the tube.* the tube is 8mm, i think.* Its best to put the tube back in first then the jet. that may be too hard. So put the new jet on the tube and put the assembly back in while holding the throttle open.* This will keep the needle from getting jammed up. snug up the jet and put everything back.* Before you do the jet change, race a buddy who is close to you, tie to 4 bikes win or lose.* Then you can do the same after the jet change to see the difference.* Stay in the range of 168 to 178 on the main, I think you will fall between those #'s.* Oh, and have fun!!!!

Thanx bro...well, b4 i got ur post i had already jetted, i threw in a 175 main, and a 48 pilot. Havent changed the needle tho caus edont know how. Also dont know how to mess with the fuel mixture screw. But she fired right up, and i just got the slightes pop when revving her up. Not that bad. Took it next door to an open grass area, and it wheelid so easily. Didnt have enough room to open it up tho. Will hopefully try this weekend. U still think its too rich? Just let me knowman...thanx
oh yeah, and how did u mod the stock muffler.Can u tell me what to do and what affect it had. Thanx

[pahrump]

The jetting sounds spot on except for the needle which you know. I would get the YZ needle but you could keep your stock needle and put it on the 6th spot from the top. To get to the needle just loosen the carb again and tilt the top towards the right side of the bike, on the top you will see a cover tht says FLAT and CR (FCR) you will see two allen bolts, remove those, and take the cover off, inside you will se another allen bolt this one is a little bigger than the ones on the cover, remove that and the needle will be under that, use a very small pair of needle nose pliers or tweezers to take the needle out. You will see the clip on the needle, pull it off (don't lose itand then put it back on at the 6th spot counting from the top (flat end) re-insert the needle and put it all back together. Fire her up and speed away.

I do not think you will need to go up to the 180 main especially with the temps starting to drop.


Scott

[pahrump]

Originally posted by rude5321@Oct 20 2003, 10:22 AM
Please forward me a copy of jetting instructions---
thanks
rbsilva1@cox.net

Sent the instructions to you...

[rude5321]

Originally posted by Pahrump+Oct 20 2003, 07:29 PM--></span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Pahrump @ Oct 20 2003, 07:29 PM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin--rude5321@Oct 20 2003, 10:22 AM
Please forward me a copy of jetting instructions---
thanks
rbsilva1@cox.net

Sent the instructions to you... [/b][/quote]
Thnx Bro' It really helps!!!!

[Kirklandrock]

send me the jetting instructions also.... just bought a 165 main and a 45pilot today..... havent had a chance to install... my quad is all stock...... and I live in Florida.... Sea Level I believe... the shop that I went to didnt have a 168 main..... gonna order one though.....
Gonna try to use the GYT-R "WR" exhaust insert..... it supposedly helped the WR quite a bit.....
Gonna get the yz needle also....
airbox lid off and gyt-r wr baffle.....
Later
Joe
joe_kirkland_2000@yahoo.com

[RCRob]

I hate to be a me too but I have jetted my 450 but I am still have a hesitation on the bottom end. Can some one send me the instructions? :re

rowland@carolina.rr.com

Thanks in advance.

[edgerat]

the low-end hesitation problem cannot be fixed with jetting. Big Pumper carb will do this.

[brad c]

ok im in southern indiana and its getting colder here.. i have a 45 pilot and a 165 main now, should i go up to a 170 main for the cold temps? will it still be ok to ride with the 170 if i put the baffle back in sometimes?

thanks

[GPracerX]

Originally posted by edgerat@Oct 22 2003, 02:56 PM
the low-end hesitation problem cannot be fixed with jetting.* Big Pumper carb will do this.

or EFI

[edgerat]

yeah Kevin, when are you going to get your guinea-pig buddy to get going on that? I am still interested in doing it.

[jamiesel]

Originally posted by GPracerX+Oct 24 2003, 07:38 PM--></span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (GPracerX @ Oct 24 2003, 07:38 PM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin--edgerat@Oct 22 2003, 02:56 PM
the low-end hesitation problem cannot be fixed with jetting.* Big Pumper carb will do this.

or EFI [/b][/quote]
have you got a optimum power fi?

[tazz888]

HI All,

I've been checking this fourm out for some time and finaly registered.

I ordered my YFZ450 today and also ordered a bunch of mods. I can wrench on a bike with no problem but jetting has always confused me. By what I have read so far you guys know your stuff so I hope you can help me out.

I will have the following mods done to my bike as soon as I get it home.

1. air box lid removed
2. K&N filter w/ outerwear
3. Curtis Sparks full exhaust
4. ZIP-TY fuel screw
5. YZ450F exhaust cam
6. NCVQ needle

Any help with jetting choices and fuel screw setting would be a big help.

Elevation: sea level
Temp: 70-90 deg

tazz888@hotmail.com

[blaktopr]

As for that bog when you just mash the throttle from idle. It can be fixed. As soon as I get some small air jets to experiment size, ill let everyone know. Basically its in the excelerator pump. There is a small air jet in the BOWL of the carb. That controls the amount of fuel squirted when you hit the gas. That is there to take care of the sudden lean spot you get when the throttle is opened. Like everywhere else that is getting richened up in the carb, that too needs to be richened.

[z-hindle]

Hi everybody!!!
I've a complete curtis spark pipe and i want to jet my bike but i don't know i'm at what sealevel??????
know i've 172 main and teh rest is stock!!!!
please help me!!!
i'come from québec canada!!!!
thanks!!!
mike

[norcal450]

Originally posted by z-hindle@Nov 5 2003, 10:45 AM
Hi everybody!!!
I've a complete curtis spark pipe and i want to jet my bike but i don't know i'm at what sealevel??????
know i've* 172 main and teh rest is stock!!!!
please help me!!!
i'come from québec canada!!!!
thanks!!!
mike

from canada eh?! sorry man i had to. my girlfriend is actually from toronto and im a hockey fanatic so nothing wrong with canada.

anyway....
i would first find out what elevation your at. if your at sea level or below 1500 ft i would go with
48 pilot
175 main
1.5 turns out on screw
gyt-r needle 4th clip

now this is with a k&N filter and lid off and cam mod

[wildtxn]

alright guys,

I have been reading through all of these but still a bit confused. I am at sealevel and have a brand new yfz450 arriving today or tomorrow. Since i haven't ordered any additional parts yet I have a few questions to ask.

First, should i go through break in before performing the yz cam exhaust mod? I am currently stationed in the middle east and it takes forever to get parts so have weeks before i can get anything through the mail. What should i do to my stock jetting once performing the exhaust mod?

second, I am ordering a FMF T4 16" and a powerbomb exhaust setup, a k&n airfilter setup as my next performance upgrade. I'm not sure which jet suites me best for all of the mods. what jet should i order and what setting should i use? i'm on a small island at sea level so think what was originally posted should be spot on target.

last, the dust here is super thin and i'm kinda weary about doing the air box lid removal thing. are there any aftermarket parts out there to replace the lid with some sort of breathable filter or screen device to reduce amount of dirt intake?

[edgerat]

I will try and remember to answer all your questions at once here.

First, the break-in can be done anyway you like but MANY of us on here broke our YFZs in according to a study that says if you break it in by riding it very very hard you will get the best performance out of it. The reason for this is when you break it in under these HI loads the rings seat better and you dont glaze any of the parts.(thats the jist of the study) You can break yours in however you like. You can do the cam mod before you even start the thing if you like. I would recommend breaking it in with the sparky out and then after you have some fun on it, go ahead and do the cam mod.
Second, you will want to order either the GYTR jet kit or the www.jdjetting.com jet kit. I have spoken with a few guys from the UAE that said JD would not ship kits over sees. So that leaves you with Bob at Magnolia Yamaha. 877-243-3337 he is Arkansas so just time your calls about the same time you would call home to TX. Once you order the GYTR jet kit you will want to install the 45 pilot jet and the 165 main(if you still have the stock exhaust on) jet or the 168(if you have installed your FMF system) main jet. Also install the NCVQ needle that comes in the GYTR kit and put the clip on the 3rd or 4th position(you will have to do a little testing depending on the weather temperature wise). Then I would also recommend getting the Zip-Ty mixture screw so that you can easily adjust the mixture screw with the engine running. This greatly helps out your tuning by being able to do so.
Third, the above jetting specs are for the complete exhaust system with the lid off your airbox and a K&N installed. If you buy a K&N kit for your 450 I would highly recommend spending the extra 10 dollars and getting an outerwear to go around the K&N. Unless you have the finest dust in the entire world you will be just fine with this setup. Your other option is to run BOTH an outerwear and an www.ehsracing.com breatheable airbox lid. All these are is a modification for your stock airbox lid. You cut out the lid and then put an outwear over it. That way you would have double dust protection.
If you do all these things you should be a very happy camper.
Lastly, I would like to take this opportunity to thank you for defending our country in the middle east. All of us at YFZcentral truly appreciate your sacrifice.
Isaac Jarrett

[wildtxn]

Isaac,

Thanks a ton for the comments and for answering all of my comments. I'm also an avid RC fan and have broken in my Nitro engines the same way.......FAST. get better performance that way, just hadn't seen any break in instructions or suggestions for the thumper yet.

I fortunately have what's considered a US address so may be able to get the jd jet kit and will try to go that route rather than the gyt-r first. mainly because the gyt-r comes with the single needle and the jd comes with both. i don't know that i will need both, but i may end up having to rejet when summer comes around here cause man is it hot. I will take a couple of test runs once doing the air box mod and see how i stand in the conditions i'm in here.

Thanks again and i will make sure to return and post my comments on setup once i get everything installed and running smoothly.

THanks again :yfz