yamaha 426 jetting problems

hello everybody I'm having problems with my jetting on my 426 i bought it new in 2002 and try ed different settings and I'm still fouling plugs i started with stock setting witch are 162 main,42 pilot, and needle is on #4 position.

i changed to a 155 main and dropped the needle one position and left the pilot at 42. my pilot screw is about 1.5 turns out . i am riding at about 4 to 6500 elevation and temps around 40 to 90 degrees. I'm steel fouling plugs and most of the time its hard to start. if somebody could help with my jetting problems i would be sooooo happy thanks

I have only had this bike for about 6 mo. and i did have to change the plug because it was becoming hard to start. not sure if the guy i bought it from putted alot or if there are jetting issues yet, i have not hade the urge to pull the plug and look yet. Mostly because some japanese genius made it real fun to check! :) Good luck ,sorry i can't help.

I would definitely put in a smaller pilot. Try at least a 40 and maybe even a 38. You run what I'm running at sea level! The MJ sounds fine, needle may be OK as well.

thanks ill try 40 pilot this weekend and let you guys no how it worked thanks for the imfo.

Search for motoman 393 site and look for the jetting chart. It'll give you some nice baseline settings for your temp and altitude.

hello everybody I'm having problems with my jetting on my 426 i bought it new in 2002 and try ed different settings and I'm still fouling plugs i started with stock setting witch are 162 main,42 pilot, and needle is on #4 position.

i changed to a 155 main and dropped the needle one position and left the pilot at 42. my pilot screw is about 1.5 turns out . i am riding at about 4 to 6500 elevation and temps around 40 to 90 degrees. I'm steel fouling plugs and most of the time its hard to start. if somebody could help with my jetting problems i would be sooooo happy thanks

desertfox89

visit www.motoman393.thumpertalk.com Your questions should be answered! :)

I have an '01 426 and used this setup when I lived in Colorado. I was riding 5000 to 11000 feet and 50 to 90 degrees with this jetting. It was maybe a touch on the rich side for average conditions, but I didn't foul plugs and I like to run my bikes that way to be on the safe side. I wouldn't hesitate to try a 38 PJ if you want to lean it out some.

Main Jet: 158

Pilot Jet: 40

Needle: OBEJP (I believe this was stock on the '01, not sure about the '02)

Clip: 4th position

Fuel Screw: 1.5 Turns (2 turns if it was cold)

Hope this helps. By the way, as motodad393 pointed out, definately check out Motoman's jetting chart. It's a great reference and will get you in the ballpark.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now