jetting=more power ?


5 replies to this topic
  • REBELEX

Posted May 24, 2005 - 01:00 AM

#1

Hey TT's, i got this 99 WR400 a few months ago and have done all the "free mods", plus an after market pipe. But so far i am still dissapointed in the power it produces. The only thing i havnt done is rejetted it. By rejetting will i see the true power of this bike. Also wats the difference between the jd jetting kit and rejetting using a OBEKP needle :)

  • C-ya

Posted May 24, 2005 - 02:57 AM

#2

Hey TT's, i got this 99 WR400 a few months ago and have done all the "free mods", plus an after market pipe. But so far i am still dissapointed in the power it produces. The only thing i havnt done is rejetted it. By rejetting will i see the true power of this bike. Also wats the difference between the jd jetting kit and rejetting using a OBEKP needle :)


A motor is an air pump. If you open the intake and exhaust, you have given it the capacity to move more air more easily. To effectively move that air, you must give the motor more fuel, otherwise you risk running lean and damaging the motor. By rejetting, you will MOST LIKELY see more power. I'm almost betting that the bike had more power before you did anything than it does now, simply due to the fact that the air/fuel ratio is now wrong.

What did you ride before this that it disappoints you? I have a '99 WR as well, and I can't believe the grunt down low and the top end this thing has - but I'm comparing this to an '84 RFVC XR200R (dual carb). The WR will pull the front up thru 3 with NO probs. The XR - usually at the start of race when I dumped the clutch, but kinda hard to do any other time. I'm still playing with the jetting on mine (main jet), but we can compare notes if you'd like.

I'll let someone else answer the needle question. I have a YZ400 needle (OBVDR) in my carb...

  • BOULMAN

Posted May 24, 2005 - 06:35 PM

#3

I just sold my 00 wr400 and it pulls really hard off the line with no dead spots. The 426 I just got, it was a jetting mess. I got it pretty close before I put the jd kit in (just to see what I could do on my own). With the kit it will it pulls hard with no dead spots :) .

If you add more air flow and free up the exhaust you have to dial the fuel and air delivery in the carb as well.

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  • REBELEX

Posted May 24, 2005 - 11:24 PM

#4

well i had two really well-setup bikes, cr80/125 with full engine work etc, so it was kinda a shock when i got the wr. the free mods had woke it up, but i knew there was something missing in that 400cc engine. id say re-jetting is the key :)
thankx for the info and when i start messin round with the jets ill post em to ya. :D

  • alexrobinson

Posted May 24, 2005 - 11:59 PM

#5

Just had my WR450 2004 model in at the Dyno Centre to check the jetting. I have had it 1 year and when I got it had spent days messing with the jetting but ended up back at standard settings. I can't believe the difference proper jetting at the Dyno made, it is like a different bike, I got 15% more torque and 12% more horses, turns out the standard settings were way too lean. I wasn't looking for more power, but I did want more traction/usuable power on slippery climbs and that is what the bike has now with the correct jetting. My advice to you would be to book into a reputable dyno/tuning centre and get the jetting set up right, that way there is no guess work and the results are there on the screen. I wish I had taken it to the Dyno from new. Next new bike I get will be going straight to the Dyno before I ride it, no more guess work for me.

Cheers, Alex Robinson UK

  • C-ya

Posted May 25, 2005 - 03:55 PM

#6

well i had two really well-setup bikes, cr80/125 with full engine work etc, so it was kinda a shock when i got the wr. the free mods had woke it up, but i knew there was something missing in that 400cc engine. id say re-jetting is the key :)
thankx for the info and when i start messin round with the jets ill post em to ya. :D


Yeah, I guess coming from a 2-stroke, the feel is pretty different. I have only ridden two 2-strokes, both Gas Gas's, and I rode them back to back. I could tell the difference from the 125 to the 200, tho. 125 was way more peaky, and you had to be "on it" to get anything out of it. If you had a well set-up 125, then the 400 4-stroke prolly feels kinda sluggish.

I have always ridden 4-strokes, so going from my XR to the WR - WOW!! Night and day difference. You'll just have to get used to the different feel of the power and the delivery. That's why I like a 4-stroke for off-road - you can lug it around like a tractor if you need to. Of course, after my last attempt at a race, I can say there would a big plus for a light weight 2-stroke in those tight woods.

Good luck with getting yours sorted out.




 
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