Carb. Settings and Jetting 02 426

[mx_scottj]

I have an 02 426 and it has a bog off bottom when you crack the gas hard, but every where else is fine. This is at about 1200 feet above sea level in kansas. Any comments would be appreciated

 

[Thump]

I am in the same boat. Big time bog off bottom is really starting to bug me. Hot an humid here in Dallas.... any suggetions appreciated.

 

[biglou]

Leaner-Start off turning the pilot screw in by 1/4 turn increments. If you are within a turn or less of bottoming out, drop the pilot jet one. Also, check into the BK mod. I have the files and the pics if'n ya want 'em. Just let me know. (Now that I got DSL, sending the big stuff is no problemo!)

Remember Rich's "Three H's": Height, heat and humidity will generally require you to jet leaner for optimum throttle response. :)

 

[sfc crash]

bk mod gets the nod from me, curred that bog. but for gods' sakes gentlemen, these are very powerfull machines....be carefull :confused:

 

[biglou]

Here is a link to motoman393's website: Click!

On the left side of the page, click "Tech Articles". From there, you will see choices for several tech articles. Click "BK Mod", then you will see two links, one for pictures of the BK mod and one for detailed instructions for the mod.

 

[sfc crash]

oh yeh another thing, my riding style is so "top pro" :confused: that i "need" a bike that will stand straight up when becond via my right wrist, so i got the wr, yz carb settings, bk mod, r4 exhaust and 52 tooth rear sprocket..if there's a bog..well, it's waay back there where it yanked my arms outa the socket...i guess top riders like us "need" that snap. :aj:

 

[DAN YZ426F]

Can Anyone Tell Me The Stock Jetting For My Yz426f 2000. Ive Fitted A Full Dsp Titanium Race Pipe And Need To Know If The Jetting Needs Altering.

Dan U.k

 

[biglou]

I think 42 pilot, 168 main and 1.5 on the fuel screw is a good starting point. Might go up to 173-175 main with the aftermarket pipe, and up to a 45 on the pilot if its 40 deg f outside or colder. Adjust fuel screw for best throttle response and "in-between" pilot jet sizes.

 

[Hick]

Can Anyone Tell Me The Stock Jetting For My Yz426f 2000. Ive Fitted A Full Dsp Titanium Race Pipe And Need To Know If The Jetting Needs Altering.

Dan U.k

42 pilot
162 main
EKR needle, middle clip
1.75 turns out on idle mixture (or fuel) screw

The stock YZ exhaust* is not very restrictive, in my experience changing the exhaust to most aftermarket systems doesn't require much adjustment, provided the bike was jetted well to begin with.


Sometimes the idle mix need tweaking, but that is about it.

Unfortunately, the '00 YZ is not jetted that well to begin with. Do yourself a favor and update the needle to the '01 part. Yamaha PN: *5JG-14916-JP-00, needle code is EJP, stock setting is middle clip...

...this change is worth as much as the BK mod, which limits the accelerator pump, which is overly generous, particularly on the '00 model.





* I'm not sure if the Euro YZ has the same exhaust as a US version. Or even the same jetting.


Hope this helps.

 

[Matt90GT]

First I would suggest to get a longer fuel screw like sold through ZipTy Racing. It is a must have on the FCR carbs.

2 things you can do for the 2000-01 bike.

1. Update the needle and AP diagaphram to the 2002 426 parts. It is the Accelerator pump (AP) squirt duration that is giving you the bog.

or

2. Buy the JD jetting kit, set it up as suggested in the directions and do the BK mod to the carb.

I did the BK mod and the JD Jetting then adjusted the fuel screw on my 426, and when warm there was no bog at all. It just takes some time to dial them in.