Helping a buddy get started with a wr426f


8 replies to this topic
  • bigtooth

Posted May 05, 2009 - 09:04 AM

#1

Hi guys,
My bud just bought a '02 wr426f. It only has 300 miles clocked and looks super clean.
I have been doing some research here for him to try to help get basicly uncorked and jetted correctly. I have come up with a list that I was going to give him and was hoping you guys could give it a once over and let me know what you think.

Shorten the throttle stop:
I found this great page:
http://www.thumperfaq.com/throttle.htm
But it says its for the 250, to the same measurements apply to his 426?
Also, is it safe to do this mod and not disconnect the grey wire?

Gray Wire:
Same questions as above, is this nessecary, does it make that much difference?

Remove the pea shooter baffle from the muffler:
Wow! I couldnt beleive the restriction when I saw that thing. Hes already removed it but i'd like to help rejet if needed.

Remove the snorkle:

Rejet:
So looking at the jetting database, and being in Vermont, so running from about 200- 1500 ft I was going to suggest the following if he completed the above:
Putting in a 168-170 main, and a 45 Pilot.

I'm just hoping i'm not to far off from a good starting position, thought some you Yamaha vets could confirm or deny.
TIA!

  • spin9

Posted May 05, 2009 - 10:46 AM

#2

I would highly recomend doing the gray wire mod. I worked at a shop in colorado and we did it to every WR that came in. It is totally safe for the bike, all it dose is change the WR ignition to the YZ timing curve. If you don't like it you can allways change it back.

  • GCannon

Posted May 05, 2009 - 11:05 AM

#3

Do the BK Mod to the accelerator pump system and get an adjustable fuel screw while your at it. Both very cheap mods that will make a big differnce.

http://motoman393.th.../tech/carb.html

When you finally get the carb and Idle dialed in perfect adjust the TPS but not until all other tuning is done. This is a bit more advanced mod but still free.

  • davidl9999

Posted May 05, 2009 - 11:13 AM

#4

Shorten the throttle stop:
I found this great page:
http://www.thumperfaq.com/throttle.htm
But it says its for the 250, to the same measurements apply to his 426?

yes.

Also, is it safe to do this mod and not disconnect the grey wire?

yes.

Gray Wire:
Same questions as above, is this nessecary,

only if you want a fast WR.

does it make that much difference?

yes.

So looking at the jetting database, and being in Vermont, so running from about 200- 1500 ft I was going to suggest the following if he completed the above: Putting in a 168-170 main, and a 45 Pilot.

That's in the ballpark, but you really need to test the bike after making that change. I'm running a 45 PJ/175MJ. at 800' and 75f. I'm going to a 42PJ. My MJ is fine. ('09 WR450F, not stock)

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Pooley

Posted May 05, 2009 - 12:19 PM

#5

This is my bike, it is an 01, but is identical to the 02:
Year: 2001
Model (400 - 426 - 450): Yamaha WR 426
Cam Timing (WR/YZ): WR timed
Main jet: 168
Pilot Jet: 45 (or 48, I don't actually remember)
PAJ: 100
Leak Jet: NA
Starter Jet: 65
Fuel screw (turns out): 2 turns out
Needle Model/Clip position: JD Red #4
Grey Wire Mod (Y/N): Yes
TPS Connected (Y/N): Yes (not re-adjusted from factory)
Airbox Snorkel/Lid (on or off): Airbox lid off
AIS Removed (Y/N): NA
Airfilter Brand: Twin Air w/ No-Toil Oil
Exhaust Brand: FMF Q
Average Altitude: 700ft (Michigan)
Average Temperature: 70-90 F
Average Humidity: 70-90%
Degree of Satisfaction (0-10): 9 (we can always want more can't we?)
Additional Mods/Comments: Additional mods:
Light Blue Wire
O-Ring Mod
ACV disabled (which is why I have a 100 PAJ rather than a 75 stock)
YZ throttle stop

This is the list of my bike settings/mods. The combination of a new exhaust and O-ring mod were the 2 most dramatic thing done. It cleaned up the low end bog, and unleashed a lot of extra power, especially down low. I did the BK mod to the carb and personally found that the O-ring mod was far superior, so I no longer have the BK. The carb should still be tuned such that the spray of gas just misses the slide. The Power Now intake mod also got good reviews, but I never tried it.

There are also some things to look for and protect against. The main one was that the chain slider rubber on the top of the swingarm does not fit snugly. It will rattle/slide around and will eventually wear away the aluminum underneath. To fix this, cut a piece of innertube, foam or whatever which will snug this fit up, and protect the swingarm better.

If I think of anything else I'll post again, or edit this one.

Tell your buddy to hang on, doing the mods opens up a whole new monster.

  • bigtooth

Posted May 06, 2009 - 04:55 AM

#6

Thanks alot for all of you input. So I guess to get started were going to try:
Removing the insert from the exhaust
removing the snorkle
shortening the throttle stop
unplugging the gray wire.

I'm sure we'll be running lean after this so i thought we'd start with the
168 main 45 pilot

I see alot of talk about 'JD' needles and jets, I saw the kits on TT for like 70 bucks is this the kit most generaly used?
http://shop.thumpert...DJETTING_JETKIT

  • YamaLink

Posted May 06, 2009 - 07:42 AM

#7

And not to stray off topic, but to ensure he gets the most out of the increased performance, help him set sag and get that power to the ground!

http://www.tootechra...ension_tips.htm

  • liverpoolone

Posted May 07, 2009 - 12:10 PM

#8

do you ned to do these mods to a uk bike year 2000 ?

  • davidl9999

Posted May 07, 2009 - 01:31 PM

#9

No AIS in that year. The Aussie bikes come with the grey-wire mod done; not sure the UK ones do (I think they do too), but it takes all of 30 seconds to check. The rest of the mods probably apply in one form or another.




 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.