WR jetting help


12 replies to this topic
  • MotorCycleMike1

Posted October 06, 2008 - 08:05 PM

#1

I have a 04 WR 450 I have a hesitation if I wick the throttle from an idle. It will not do this if I give it a little throttle before I rev it. 168 main, jd blue 3 from the top. I read in the FAQ a 40 leak jet will do the trick I tried that, still didnt work.. I do not know if there is an adjustment to a accelerator pump, I looked in my manual and could not find anything.

Im lost please help!

Thanks Mike

  • simica

Posted October 06, 2008 - 08:59 PM

#2

There are some things you can do to help and you're on the right track. Proper jetting settings, Power Now valve, new Accelerator Pump cover; all I have done to my '05 and it has made a huge difference. But if I stand next to my idling bike and jerk on the throttle, yes it still hesitates a little, especially if the motor is cold. I have also added the YZ cam and after market pipe and I am very happy with the throttle response. I think all WRs '06 and older have this hesitation no matter what you do. The '07 and '08 rev more like the YZ and there is less hesitation. But be realistic, in most riding conditions, even MX, having to twist the throttle that quickly doesn't happen very often if ever. I ride/race alot and have never been in a position where I had to twist hard and the bike didn't respond adequitely. My two cents.

  • buggs bunny

Posted October 07, 2008 - 06:25 AM

#3

mabey do the o ring mod.it tightens up the free play so when you hit the gas the reaction to the accelerator pump is faster.

  • jobfnl

Posted October 07, 2008 - 02:25 PM

#4

Mike,
Go to the jetting forum and read the sticky about setting your fuel screw/pilot jet sizing before you spend bucks on parts. Pilot jet meters fuel down low before it really gets to the main. This should help.
Jeff

  • Charles De Mar

Posted October 07, 2008 - 05:25 PM

#5

check out the YZ450 service manual. It will help you jet the bike. get rid of the JD needle. best thing I did to my bike was lose that needle. Or don't:thumbsup:

  • kskyles

Posted October 07, 2008 - 06:17 PM

#6

i would try the 40 leak jet first of all. it's cheap and easy to do.

i run a jd kit with a 40 leak and never have the bog. the 40 leak also got rid of the bog on my wife's wr250.

if it doesn't work, then start with the basics(pilot circuit setting, needle height, etc).

you'll get it if you read through the jetting sticky, and the manuals.

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  • MotorCycleMike1

Posted October 07, 2008 - 07:39 PM

#7

Thanks for the replys. Charles, what did you put instead of the JD needle?

  • Ramcc4x4

Posted October 07, 2008 - 07:39 PM

#8

I guess I'm one of the "lucky" ones. I can twist the throttle as fast as I can and there is no bog. I even run an open side panel. My current setup is: JD blue needle in 3rd position, "thick" o-rings for accelerator pump, 48 pilot, adjustible pilot screw, stock leak jet, 170 main, UNI filter and DrD pipe. I've had several people ride my bike that also have WR's and they have been impressed. Sounds like you may need more fuel to eliminate that flat spot based on what you've posted.

  • Charles De Mar

Posted October 08, 2008 - 07:55 AM

#9

i would try the 40 leak jet first of all. it's cheap and easy to do.

i run a jd kit with a 40 leak and never have the bog. the 40 leak also got rid of the bog on my wife's wr250.

if it doesn't work, then start with the basics(pilot circuit setting, needle height, etc).

you'll get it if you read through the jetting sticky, and the manuals.


I am running a 40 leak jet with a boysen quick shot that seem to help the initial bog

Thanks for the replys. Charles, what did you put instead of the JD needle?

I'm running the YZneedle. There are different ones and I suggest looking at the yz450 service manual to get an idea of what you might get instead. see my jd needle thread for my experience with them. some guys have good luck with them. I didn't. I would love to ride those bikes that have riders who like the JD needle. I have no comparison to judge my opinion. Just that I wasn't happy with the JD set up.

  • William1

Posted October 08, 2008 - 09:11 AM

#10

Read this before you spend money:O-Ring Mod and AP Tuning

  • timoyz1

Posted October 08, 2008 - 10:55 AM

#11

I didn't cheap out and use a o-ring. For $15 you can get Merge APS that won't break eventually, and is engineered to the right spring rate.

  • kskyles

Posted October 08, 2008 - 02:21 PM

#12

I am running a 40 leak jet with a boysen quick shot that seem to help the initial bog


I'm running the YZneedle. There are different ones and I suggest looking at the yz450 service manual to get an idea of what you might get instead. see my jd needle thread for my experience with them. some guys have good luck with them. I didn't. I would love to ride those bikes that have riders who like the JD needle. I have no comparison to judge my opinion. Just that I wasn't happy with the JD set up.


Charles - if you're ever in AZ, give me a buzz. you can try out my bike. i would love to try out the yz needle too. i'm really intrigued by them. they're a lot cheaper, and would assume that the performance is pretty close. i'd definitely look you up to try out the yz setting. i'm glad you had some good success with it. it's good to have some comparison.

  • MotorCycleMike1

Posted March 22, 2010 - 01:33 PM

#13

i agree the o ring mod seems like it may not hold up? has anyone had any experiences with a new accelerator pump cover?




 
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