Another 426 carb issue


10 replies to this topic
  • frankie_b_jr

Posted December 30, 2011 - 06:30 PM

#1

Did a little trading for an 01 426 in the spring. It would start and run fair. When the guy show me the dance for it he said he had never used the choke to start it. After 2 weeks of playing with the jetting daily:foul:, i got it running great but i'm still having an issue:banghead:. The choke is WAY to rich. The whole system runs rich until it is fully warmed up. After it warms up if you pull the choke it will kill the bike, then i have to use the hot start to start it again.
Any ideas? Thanks ahead of time.

Jetting info...

165 main
42 pilot
72 starter
100 paj
200 maj
dynojet stage 1 needle (kit)
fuel screw 2 turns give or take 1/2 turn for conditions
3000- 6000' elevation
Less than 30% humidity
30- 60 degrees currently... up to 110 in the summer.

  • 2grimjim

Posted December 30, 2011 - 06:38 PM

#2

The original starter jet was a 65. If you have a 72 that woul explain a lot. What is your float level set at?

  • frankie_b_jr

Posted December 30, 2011 - 08:37 PM

#3

The float is just over book spec (can't remember the numbers off the top of my head) to help lean the whole system slightly. I thought that 72 was stock. Guess thats what i get for doing my own thinking again.
Any thoughts on where to find jets online? The closest yama shop is about 200 miles away.
Thanks.:bonk:

  • frankie_b_jr

Posted December 30, 2011 - 09:03 PM

#4

This was in the 426 jetting database, post #6

OEM 2001 YZ426F(N) and 2002 YZ426F(P) Jetting:

Main Jet: 162 Pilot Jet: 42 Starter Jet: 72 Leak Jet (if any): N/A Fuel screw/Setting: 1.25 - 2.0 turns out Needle/Position: OBEJP-4

  • grayracer513

Posted December 30, 2011 - 09:26 PM

#5

This was in the 426 jetting database, post #6

OEM 2001 YZ426F(N) and 2002 YZ426F(P) Jetting:

Main Jet: 162 Pilot Jet: 42 Starter Jet: 72 Leak Jet (if any): N/A Fuel screw/Setting: 1.25 - 2.0 turns out Needle/Position: OBEJP-4

That info was directly from the manual, although it would not surprise me to find 100% original carbs with three different configurations.

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  • frankie_b_jr

Posted December 30, 2011 - 09:59 PM

#6

Thanks grey. I use to see that a lot with my honda atc's. I was hoping that the newer manufacturing standards were higher than that. Had three carbs once... one was sold in california, one in utah and one in colorado. Each was stock but factory jetted for the elevations. Do manufacturers still do that? If so, this was a sealevel bike... does 65 sound right to you? Sounds like a big jump to me. Second question... where might i find one without the 200 mile drive (one way)?

  • grayracer513

Posted December 31, 2011 - 07:56 AM

#7

For sea level at 70 degrees, the starter should be somewhere in the area of #70, but it really isn't that critical. My '06 has a 70 in it and works in a very wide range of situations and altitudes.

Some of what you say is contradictory. Warming and engine up will not make it run leaner, in fact it's just the opposite, which is why enrichening devices like chokes are used for cold starts.

Have a look at the vacuum release plate on the engine side of the slide to be sure it isn't chipped or cracked, or installed upside down (the square edge with the small hole goes down).

  • 2grimjim

Posted December 31, 2011 - 03:55 PM

#8

The original starter jet was a 65. If you have a 72 that woul explain a lot. What is your float level set at?


This info came from Yamaha's parts fische. Couldn't tell ya what was in the service manual.

Parts fisch will sometimes reflect changes that were made after the service manual was printed.

  • grayracer513

Posted December 31, 2011 - 08:33 PM

#9

Whether the parts fiche remains current or lags behind is sometimes unclear, but they do certainly differ with the service manuals as to jetting and some other things, like suspension parts.

  • frankie_b_jr

Posted December 31, 2011 - 08:39 PM

#10

This info came from Yamaha's parts fische. Couldn't tell ya what was in the service manual.

Parts fisch will sometimes reflect changes that were made after the service manual was printed.

Thanks for the clarification.

For sea level at 70 degrees, the starter should be somewhere in the area of #70, but it really isn't that critical. My '06 has a 70 in it and works in a very wide range of situations and altitudes.

Some of what you say is contradictory. Warming and engine up will not make it run leaner, in fact it's just the opposite, which is why enrichening devices like chokes are used for cold starts. I understand and agree. That is why i included it. I'm not certain that it is rich, it just shows the symptoms for the fisrt 15 minutes or so of riding.

Have a look at the vacuum release plate on the engine side of the slide to be sure it isn't chipped or cracked, or installed upside down (the square edge with the small hole goes down).

I have inspected it closely and even put it in upside down to see what
happens. That was before i found this amazing site. THANK YOU VERY MUCH GENTELMEN for you time and expertise!:bonk:


  • frankie_b_jr

Posted July 07, 2012 - 03:58 PM

#11

Hello all. Resurrecting this after 6 months because i am still having the same problem.
After 6 months and 50 dollars worth of starter jets, plus shipping, it still floods instantly when i pull the choke. I have dropped clear down to a 50 starter jet, and still just a black puff of smoke as it dies warm and a soaked plug cold. Thankfully i don't need it when the temps are above 70 so i still get to ride regularly without killing my leg first thing.
Anyone with any ideas please put them out here for me. Everything else is spot on and the bike runs great. Just wish i didn't have to start it 7 or 8 time to get it running on cooler mornings.





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