i just put a big gun complete pipe and a kn filter with no air lid, and outer wear. i have a dynojet jet kit and it said to put a 150 main jet, needle on 5th slot, and turn screw 2.5 out. i tried this and it wont idle now without giving it some gas. and when i rev it high it backfires. does anyone have some settings i could use or some sort of tips, its my first time doing any jetting

 

Thats because dyno jet kit doesnt come with a pilot jet.

 

So you need to get one from your dealer.

 

i'm sorry could you explain a little about what i need one for and what it does, and what type

 

Try going to a 180 DJ main,,,,,,,,45 pilot,,,,,,,3.25 air/fuel screws,,,,,,,4th clip from top on needle,,,,,,,no lid, good luck [img]i/expressions/face-icon-small-wink.gif[/img]

 

Dyno jet is different from other jet kits. The highest main they send it 150 i think. The kit does not come with pilot jets. So you need to get a pilot jet. You can try 45 or 48 and decide yourself which one works better.

Oh and i quoted the wrong person but i dont feel like fixin it [img]i/expressions/face-icon-small-happy.gif[/img]

 

You can order DJ mains direct DYNO JETS web site

As far as pilots go to your yamaha delership and tell them what your looking for

 

Did you turn the idle up? It is the black **** on the side of the carb and needs to be turned quite a bit to make a difference. Turn it clockwise until the machine will idle on its own. Whenever you make changes to the fuel screw, you will often have to adjust the idle.

I have no idea how dynojet could think the stock pilot size is fine. It is on the small side even for a stock machine (get a 45 or 48). You would have been better off to just buy a main, pilot, and needle from your Yamaha dealer.

Make sure your rubber boots are tight on either side of the carb.

 

ok i did this setup and its up and idles, that jet kit was pretty worthless i guess. i havent gotten to ride and test it yet but isnt 180 main jet kinda a big jump from the 150 the stupid jet kit recommended

 

pilot 45 (biggest in the gytr jet kit for the YFZ450) airscrew 2 and mainjet 165 (Biggest in the Yamaha jet kit)and needle clip stock #4 is my advice to anyone buying a 450 right off the shelf, if you remove the baffle and the airbox lid then put the needle on #5 clip.

IF YOU BUY A PIPE then get a 170 mainjet at least usually unless you are at altitude of several thousand feet..

THAT IS ALL YOU HAVE TO KNOW! Popping and crackling and a little hesitation, is not much problem it won't hurt anything, and your tail pipe will glow RED! It is cool at night! Don't melt your pants. This won't cost you any money except a 6 dollar pilot and a 4 dollar mainjet.

The first change is alway a bigger mainjet then one up on the needle clip, then a bigger mainjet again. When you think you have it right, then you need to take out your spark plug and put in a new one. check the old one and see what color the electrodes are. This tells you if you are jetted safely. If there is a LOT OF WHITE or chalk color on the electrodes, then you are runniing too hot and too lean.

If the electrodes look BLACK and like PENCIL LEAD COLOR you are too rich and need to go down a main jet and try again. Or down a needle clip. CHANGE ONLY ONE THING AT A TIME. IF you have the cam mod you should run pilot 48.
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NEVER go below a PILOT OF 45! for any reason.
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NEVER go below a mainjet of 165 for any reason. NEVER put your needle clip below #4 for any reason on the STOCK NEEDLE!

CLIP 4 means the fourth clip counting from the big fat end. The closes notch to the big fat end is clip # 1 this is danger zone clip #2 is danger zone and clip #3 is danger zone if you do any mods clip #4 is safe for simple mods and so is clip 5 and 6.
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Looking at the plug, you will see that a good plug is light brown.

if you have white on the electrodes then you are too lean, that means your jet numbers are a little bit low, so put in one bigger one. either a mianjet or another clip up on the needle. DO NOT JUST KEEP PUTTING IN BIGGER AND BIGGER MAINJETS! the rule of thumb is FIRST put in one mainjet, THEN GO UP ON THE NEEDLE TO #4 then go u 1-2 more mainjets. then go up to #5 on the needle then go up 1 mainjet. then go up to #6 then go up 1-2 mainjets. Don't just go up only on mainjets, youll get way out of balance.

AFTER GOING UP TWO CLIPS ON THE NEEDLE YOU MUST GO UP ON THE PILOT BY ONE or you will get hesitation. IF IT WILL NOT START then go down on the pilot by one.

Hope this helps ... i used these methods to jet mine and it is good advise found in here Jet index