Question for carb experts...



7 replies to this topic
  • Nixter

Posted May 18, 2003 - 03:15 PM

#1

Just finished my second ride on my 450 & love it!! I changed a few things since the first ride - cut grey wire, Twin Air filter, Pro Moto exhaust insert. My question is, it has a hesitation from closed throttle. If you grab a handfull from idle it bogs, or in worst case stalls. Also noticed a small backfire occasionally, usually when cold.

It runs fine when I'm up to speed, but was wondering if I need to tweek the carb a little. I am running stock jets and have not touched the fuel screw. I usually ride between sea level and 1500 feet. Any help appreciated before I make an easy fix a project from hell. :)

  • ckulzer

Posted May 18, 2003 - 03:36 PM

#2

Open up the airbox and rejet. Moving more air without additional fuel just gets you into a lean condition.

I am a little fat on top (at 200lbs, I suppose that's true :)) but I don't mind giving a fresh engine a little extra fuel.

I don't notice the bog when I am riding, only when I am looking for it. If it doesn't effect you when actually riding, don't worry about it. Remember, this is not a 2 stroke. Big singles have more trouble with quick handfuls of throttle.

Ride fast-take chances

Chad

  • AK-thumper

Posted May 20, 2003 - 06:17 PM

#3

Big singles have more trouble with quick handfuls of throttle.

Chad


My bike will take a handful no problem. Zero bog. When I had a 48 pilot jet in mine I noticed the bog while I was riding but accepted it as unavoidable like you have. I don't get you 450 riders. The engine is basicly the same as the 400-426 predecessor but you guys want to make the same mistakes we made two years ago. I can't believe that noone has taken the initiative to start with the established baselines from the 426 and perfect them for the 450s. Until then i guess you can ride around with your bog.

You won't know how bad you have it until you get it right.

Cheers

  • live_to_ride

Posted May 20, 2003 - 07:04 PM

#4


Big singles have more trouble with quick handfuls of throttle.

Chad


My bike will take a handful no problem. Zero bog. When I had a 48 pilot jet in mine I noticed the bog while I was riding but accepted it as unavoidable like you have. I don't get you 450 riders. The engine is basicly the same as the 400-426 predecessor but you guys want to make the same mistakes we made two years ago. I can't believe that noone has taken the initiative to start with the established baselines from the 426 and perfect them for the 450s. Until then i guess you can ride around with your bog.

You won't know how bad you have it until you get it right.

Cheers



You're not helping any. How about you tell us how you fixed it? thanks
Chris

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  • timvv51

Posted May 21, 2003 - 02:03 AM

#5

YEAH. Tell us how to at least improve the bog. I like to be able to count on being able to lighten or lift the front end instantly. I took the 450 carb off to do the BK mod and if you noticed my earlier post on this subjet THEY HAVE CHANGED THE CARB. It no longer has the little tab you drilled in to to put the accelerator pump limiting screw in but the squirt of gas is perfect. I am still thinking I am a little lean and about to wear the clamps out installing and removing the carb checking different needle,pilot jet,pilot air jet settings. So if anybody has anything new or constructive on the WR450 I am all ears. I am about to decide to spend the money to take it to a dyno where I can have the exhaust gasses analyzed. Except for the hesitation when you whack the throttle I love this bike TIM

  • ColoradoTim

Posted May 21, 2003 - 04:56 AM

#6

Hello,
I had the 2001 and 2002 WR426 and used that jetting as a baseline. The 2003 wr450 is completely differant. After getting the jetting as good as I could get it with mains and pilots, I still had a bog down low and popping during decel. (I read somewhere on this forum that popping was normal!)The biggest improvement was when I put in a stock YZ450 needle. The bog is gone and so is the popping. Now I'm at 160 main, 42 pilot, airscrew at 1 3/8 turns, stock YZ needle at 4th position. Gray wire pulled, Supertrapp pipe with 6 discs, No throttle stop or air filter plug. This set-up runs great at 7,000 to 9,100 feet.
Tim

  • timvv51

Posted May 21, 2003 - 04:51 PM

#7

Thanks, ordered my YZ needle this afternoon. Tim

  • WhyZ

Posted May 25, 2003 - 04:23 AM

#8

A P-38 could also help IMO.




 
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