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desertfox89

yamaha 426 jetting problems

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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

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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.

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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.

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

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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! :)

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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.

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