GREAT build BAD jetting???????? HELP!!!!

[mattmanz71]

ok here is my dilema... i built my warrior engine with a je 12:1 a megacycle cam .450" lift .276* duration a mild port and polish an open airbox setup with uni filter and hmf pipe. the dyno jet kit was the biggest waste of 50 bucks ever i even had to order a DJ 155 and 160 no dice with those either.. i looked on hmf's website and the recommend a 152 mikuni jet so i ordered that put the stock needle in and the new main jet still no dice bottom and mid is OK but WOT it will pop and with a blip of the throttle it will pop however the header is not glowing red or anything... HMF had no recommendation for a pilot jet... the bottom is fine so ive ruled out the pilot jet. im thinking i need a much larger main jet than hmf even recommends with the kit and my needle setting is stock right in the middle. any hint/ help would be great!

 

[20warrior00]

what color is your plug??

 

[mattmanz71]

believe it or not theres not alot of carbon on it it looks good !! which is what is irritating me! haha im about to head to my buddies house n see what happens

 

[mattmanz71]

no dice tried 2 and 4 pos on my needle with the 152.5 and the 155 main with all 3 needle positiond because bottom is ok has a horrible transition into mid and top and the top end spits and pops sounds like a fire cracker and sometimes a couple... hoping and open to all advice

 

[yamarider]

How lean have you gone on the main so far? Every build will respond differently, sometimes you can do all kinds of stuff and end up running leaner jets than stock because of the way the parts work together, it can be unpredictable. Manufacturer recommendations for exhausts are totally useless when you have other aftermarket parts installed, HMF's recommendation is only useful on an otherwise stock machine under average climate and altitude conditions.

 

[jasonp]

Yeah you want to start with the main jet. Get that on before you start dinking around with the needle. What happens when you have to rich of a main is it will studder or act like a rev limiter. The richer the main the less the engine will rev out.
Is this a warrior carb or raptor?

 

[mattmanz71]

its a warrior carb

 

[sykowarrior357]

i would try a little leaner on the main then what you have used...more mods doesnt exactly mean you have to step the jetting up, i would give a try at 150 or maybe even 147.5 then go from there...just my .02

 

[DeadLastRacing]

Save up for a Edle.....and never look back. Anyways, you probably know this already, but your elevation also has a lot to do with your jetting. Where you at from sea level?

 

[dswwarrior350]

First off

Pull the carb out and clean it like no other... blow all the jet passages with compressed air and use alot of carb cleaner. Then check all the intake rubber make sure nothing is cracked.

After that Put your needle back in the middle position if its not already.

Jump the pilot jet to a 45 and see if it runs better..... it should....

You need to get a good assortment of main jets..... a 150,152.5,155,157.5,160,162.5

And basically start with the 150 and keep swapping jets untill it runs its best up top. The best way to do this is just keep taking the main jet bigger untill it runs worse than it did on the jet before it. If it keeps running better then just keep going bigger.

Once you get the main jet figured out adjust the clip on the needle the same way....


Doing plug chops or whatever you want to call it never helped me adjust anything....mostly because i didnt like holding a freshly built motor wide open for so long. Ive always used the method above... then after a day of riding id pull the plug and check it then and readjust if needed... as long as its close to being right you wont hurt it...


My guess for jetting is
45 pilot
needle clip 1 clip up
157.5 main jet

But thats only a guess

 

[mattmanz71]

thanks ds warrior thats exactly what i was thinking but i called dennis kirk and my local dealer and no one knows where to get the bigger pilot jets where did you guys get yours from???

 

[DeadLastRacing]

Got mine from the local Yamaha dealer when I had my stocker carb. They should carry them in stock.

 

[mattmanz71]

the dealer wasnt able to get them what is the mikuni part number for the main jets

 

[dswwarrior350]

your dealer should be able to get them if you take a main jet in with you... mikuni only makes a few different styles of main jets.