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Discussion Starter #1
I nailed my new jetting on the first try this week. I'm no backyard mechanic like some of you so I have to thank daddog for the new web page he set-up. I installed a proflow kit removed my baffle and decided to go with a 170 main, 45 pilot and 2.5 turns out on the mixture screw and WOW!!!!!! what a difference. A noticable difference in both top and bottom end, I do feel a little stumble if I ride at half throttle and I'm sure this is a mixture screw ajustment but If I wanted to ride at half throttle I would have bought a honda :blah

seriously I would really like to thank all you mechanics who have helped me out in posts and IM's over the last week (selector :D ) and to daddog for the awsome web page. :yfz
 

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how do i find this webpage?
 

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what did you do with your needle in the carb? clip position? GYT-R needle? stock needle?

This may be your point where your "stumbling" in mid range
 

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Discussion Starter #5
I have the stock the needle in the 5th position?

Can someone please explain what the mixture screw does and what effect it will have on the bike?
 

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ok in im southern indiana, im not sure on the altitude..

i have the baffle out and the lid off

i have a 168 main, 45 pilot, 2.5 turns and stock needle on the 5th clip.. with it geting cold will this be ok or do i need to go to a 170 main..

thanks alot.. it seems to be running fine on the 168, i just wanna be sure im not gonna get to lean with the cold weather..
 

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Originally posted by RESCUE YFZ@Nov 19 2003, 11:12 AM
I have the stock the needle in the 5th position?

Can someone please explain what the mixture screw does and what effect it will have on the bike?
The fuel mixture screw is a low speed fuel adjusting screw. basically is controls the amount of fuel in the mix. turning it in reduces the amount of fuel in the mix, while turning it out increases it. It has the most effect at small throttle openings.

At mid throttle is where the Needle comes into play. The higher the number clip you have it on the richer it is. While the lower number the clip is on the leaner it is. I would seriously recommend getting the ncvq (yzf450 dirtbike needle) since it has a better taper, and will allow more fuel into the mix, and should solve your mid throttle "bog"

Sounds like you have your main jet right since it is not cutting out at full throttle.

good luck
 

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ok, cutting out on top...does that mean once ur up on 5th gear it seems to just flatten out and stay the same spped? Cause if so then mine was doing that when i dragged a couple times. It was wierd, cause usually if im not the one catching up after a bad start...no one is catching up to me. But this time if i didnt get one HELL of a start, My friends Z, and another banshee that i raced would creep up and pass me when im pinned in 5th....So is it a main jet problem? I have a 175 main, and the pilots a 48. Havent messed with the fuel mixture screw yet, and i havent recieved my YZ needle eithr.....Damn Chapparal
 

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no it's full throttle no matter what gear your in.

it may not be your jetting.......When I was racing at Glamis Veteran's weekend, I was running good, but then my bike started getting slower and slower...pretty soon I was just able to keep up.....ya' know what the problem was...a flat rear tire. Since I was running my beadlocks, it still looked inflated but sure enough it was flat. SO it may be something more obvious than a jetting issue...especially if it just started.....

Take a look at your bike, and see if there is something else wrong with it. Also start your motor, and run it from idle to full throttle, and see if it cuts outs, or if there is any hesitation with the response. (Don't run it at full throttle for more than a few seconds) Even though there is no load on the machine, this will help you decipher what the problem is.

If it runs fine then take it out to a place where you can put the machine under a load (small incline or long road that you can ride on) and do the same thing from Idle to full throttle seeing if there is any hesitation or cutting out. If there is then jet accordingly. But make sure once again there isn't a more obvious problem.
 

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how white will my plug be if its to lean? i just put a 170 main and ultimate 4 in it tonight and it pulls good, no cutting out or anything but i wanna be safe..

i had 45 pilot,2.5 turns,5th clip and a 168 main, baffle out, lid removed and it seemed to be fine on 93 pump gas (that should be good right ??)

i wanted to try ultimate 4 fuel so....

i now i have 45 pilot,2.5 turns,5th clip on the stock needle and a 170 main.. im running the baffle out,lid removed and ultimate 4 fuel. runs fine and pulls hard, but is this jetting maybe to lean?

ive checked my plug, its not realy any color but the metal color..thats why im lost
 

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the needle affects the main jet.

if there is a stumble in the middle then adjust the needle up one if you havnet ever adjusted it.

if it runs worse then go down one.


as for the top end, the only way you will ever find out if that 175 is the best is to try a 178 and a 172 and see which is better.

that is the only real way.

also try going up one notch on the needle and then back down.

never go below #4 on a stock needle
(4 clips from the fat end)
5 clips from the fat end is ok also if you have lots of mods

see the page

www.eskimo.com/~daddog/index.htm

it is a GENERAL idea to get you there.

you should get it adjusted till your mid range is HOT and has no stumble.

the airscrew could do it by going to 1.5-2 also there are many ways to adjust


pilot is low end
needle is middle
mainjet is top
airscrew affects the whole range for fine tuning on the 450 kind of weird, so I always start with 1.5 on needle till every runs GREAT then finally adjust the airscrew.


your welcome, soon everyone will know how to do this and we will have a lot of hot 450's out there.
that will be fun.
 
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