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Garry

OBELN needle in WR426 Can, Aus, UK with std. Exhaust: performance gains

12 posts in this topic

Hi All,

This post concerns those who have a Canadian, UK Australian (and other non US) WR426 and wish to retain the standard stainless steel muffler.

I post my experiences to provide additional tuning data for those seeking to keep these bikes close to standard configuration, yet optimize jetting.

Following the advice from James Dean (thanks!) I replaced the standard OBDQR needle (Australian market, and rich running in std. #4 clip position, ok in #3 clip position) with the OBELN needle.

Base specs are:

01 WR426, air box lid removed, standard exhaust

Altitude: 0 – 1000m (3250ft), Temp: 10-25 C

The jetting was optimized to the following:

-165 main

- OBELN needle # 3 clip position

#42 pilot 1 turn out

As has been documented, this needle gave excellent gains in mid range torque/response.

Of particular interest, and less widely documented, was the boost it gave to the WR at the bottom end of the rev range.

With the std. OBDQR needle, and std. 14:50 gearing the WR would only pull cleanly from 60kph/38mph/4000rpm in 5th gear.

With the OBELN needle the bike pulls cleanly and strongly from 40kph/25mph/2800rpm in 5th gear.

The change in needle has made the rev range from 2800 rpm to 4000 rpm far more useful, as the engine is able to produce more torque and a better response in this range (as well as in the mid range). So in addition to the other highlighted advantages of this needle profile, it also lets you match or exceed the low rev capabilities of an XR400… now wasn’t that the reason we all bought this bike?

Cheers

Garry

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Garry

my settings are also with the euro pipe on. the gains you've experienced are from the straight part of the needle helping at very low revs (2,000) and the nedle higher up at 6-8,000 revs. the piggy in the middle is your pilot circuit.

well done. and well done again james dean! what a star! :)

Taffy

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Garry,

It's good to hear you have the settings dialed-in and working for you. Thanks for the results!

It's a mutual respect Taffy :)

James

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Garry or James, Does it also make the low end of the throttle more predictable? On my US 01, 426 (airbox lid removed, grey wire cut, throttle stop cut, stock silencer with a Vortip, planning on doing BK mod in future), right of idle the bike will want to jump. Not good for the slow technical stuff. Will this jetting change improve the throttle response off idle? Would these changes apply to the US 426. Does it sacrifice from any other part of the throttle. Thanks for any help. Mike

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lomitamike,

The reported response is in the absence of the BK mod, but with the standard European/Can/Aus exhaust. Here is a description of the throttle response with the OBLEN needle cf with OBDQR needle.

Throttle Position : Revs : Response

0-1/8 : low : More sensitive, small throttle movement produces a greater response, finer throttle control required.

0-1/4 : low : Significantly more aggressive throttle response

So yes, the bike wants to jump off idle, and respond more readily at low revs relative to the std. needle, but it is entirely controlable, and readily adapted to after a short period.

I have deliberately tested it in tight technical stuff and consider this (OBELN) needle better, as even though it is more responsive, it produces more torque at low revs and hence is controlable .. also you can use a higher gear more readily to tame the power delivery.

All other parts of the throttle response are improved, the engine is more responsive though finer throttle control is required.

Interestingly, I now do fewer gear changes and use lower revs for hill climbing. It has made the bike more 'XR like' if you choose to ride it in such a manner.

My advice would be to buy a needle of this profile and try it.. the gains in all respects justify it...

Downsides? I have not measured an increase in fuel consumption

However, you'll wear out your rear tyre more readily!

Garry

[ April 05, 2002: Message edited by: Garry ]

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Garry

the USA pipe is the most restrictive that's why not a sole uses it. i believe they put a vortip in the end etc.

the euro pipe is restrictive but nobody beats it for low DB output. 82db i believe.

for those of us with tinitus it's a godsend

Taffy

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Would the OBELN needle work well in conjunction with the BK mod? Have you not done the BK mod yet??

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Dom,

In my opinion the needle provides such gains that it is worth getting regardless of whether or not you have done the BK mod.

On my bike I have not yet done the BK mod. I have a fuel sqirt duration of 5.2 secs.. however I have not had real problems with bogging.. the bike carburates well now right through the rev range (following needle change and jetting optimisation)

I'll try the reversable BK mod in coming weeks.. mainly on the basis of the fun obtained in refining these bikes.

Garry

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Is the OBELN needle a Yamaha part number, because my dealer couldn't find one in his parts books of fiches? Who could I order one from if I can't get one here?

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You want OBELN needle.

Part number: 5NL-14916-EN

it is an option for the YZ250F

Garry

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