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bigtooth

Helping a buddy get started with a wr426f

9 posts in this topic

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!

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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.

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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.thumpertalk.com/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.

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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)

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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.

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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.thumpertalk.com/ProductDetails.asp?ProductCode=INT%5FJDJETTING%5FJETKIT

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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.

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