question on fuel screw adjustment


10 replies to this topic
  • thatraptorguy

Posted September 05, 2009 - 07:05 PM

#1

i just got a 07 wr450.....it came with a full pro circuit t4 exhaust and has the ais removed....its got a red fuel screw adjustment and am wondering if i can run this full pipe and change the fuel screw settings and not be running lean...

  • Krannie McKranface

Posted September 05, 2009 - 08:24 PM

#2

i just got a 07 wr450.....it came with a full pro circuit t4 exhaust and has the ais removed....its got a red fuel screw adjustment and am wondering if i can run this full pipe and change the fuel screw settings and not be running lean...


All the fuel screw does is adjust the pilot jet circuit. You need to know all of the jets in the carb to know if you are jetting properly.

  • William1

Posted September 06, 2009 - 02:16 AM

#3

To expand on krannies comment, the fuel screw is for idle only, that is only part of the picture. You need to adjust the needle (replace the needle and move the clip) and change the main jet.

  • thatraptorguy

Posted September 06, 2009 - 05:19 AM

#4

why buy an aftermarket fuel screw just to change your idle then???that dont make much sense....and i know its running rich because when you snap the throttle really fast in neutral itll die

  • yamadog426

Posted September 06, 2009 - 06:40 AM

#5

sounds like u need some carb parts to deal with the bogging, accelerator pump spring- www.mergeracing.com- and a quickshot from Boyesen
there are a lot of threads about this problem just have to scroll through them. sticky has real good threads about this check them out they are at the beginning of this forum

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Krannie McKranface

Posted September 06, 2009 - 07:24 AM

#6

why buy an aftermarket fuel screw just to change your idle then???that dont make much sense....and i know its running rich because when you snap the throttle really fast in neutral itll die


It doesn't change your idle, it changes the pilot circuit, which changes the idle. The goal is to get the pilot circuit perfectly tuned no matter what the humidity or altitude, that's why it's adjustable. You use the change in idle to determine the correct setting. Do a search on 'fuel screw adjustment' for more details on how to do it.

You need to check you carb jets.

  • NMNORGE

Posted September 06, 2009 - 09:12 AM

#7

It doesn't change your idle, it changes the pilot circuit, which changes the idle. The goal is to get the pilot circuit perfectly tuned no matter what the humidity or altitude, that's why it's adjustable. You use the change in idle to determine the correct setting. Do a search on 'fuel screw adjustment' for more details on how to do it.

You need to check you carb jets.

That red fuel screw when adjusted properly, can eliminate the off idle bog.
Going from the stock muffler to an FMF Factory, then to a LeoVince Enduro muffler required some tweaking with the fuel screw.

With the engine at normal operating temp, run the screw in till the idle starts to climb then back out 1/4 to 1/2 turn. When finished that red screw should be 1/2 turn to 2 1/2 turns from stop. Anything outside that means you need to change jetting. JMO

  • thatraptorguy

Posted September 06, 2009 - 02:38 PM

#8

well it doesnt do the bogging anymore after riding it today but i think i got a new problem....sometimes it will idle sometimes it wont....after being on the gas hard and pulling in the clutch and coasting the motor dies...and at about a 1/4 throttle the bike will spit and sputter....the battery seems weak and i think that this is why its acting like this.....its not popping or anything so it cant be to lean.

  • Sider_steve

Posted September 06, 2009 - 04:07 PM

#9

I stole this from the 250 F forum.....

Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly). Once warmed, slow the idle to the lowest possible speed.
*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***
Turn the screw in until the idle becomes rough or the bike stalls.
if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.
If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.
Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.
If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.
If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.
If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,800 rpm, but go by the spec in your manual.
Props to William1 who originally posted this

If you set your fuel/pilot screw using this method you should get rid of all the funky traits your WR is having from idle to 1/4 throttle.
I would also read up on all the free mods,especially the grey wire mod since someone has gotten rid of the restrictive stock silencer. http://www.thumperfaq.com/index.htm

  • thatraptorguy

Posted September 08, 2009 - 05:43 PM

#10

alright thanks....i was riding it on the road today and the postive battery cable came loss and the bike kept popping and stalling and falling on its face....got it home tightened up the cable started it and it died right after i took it off choke....let it sit for 10 mins and not it wont start

  • NMNORGE

Posted September 08, 2009 - 05:49 PM

#11

alright thanks....i was riding it on the road today and the postive battery cable came loss and the bike kept popping and stalling and falling on its face....got it home tightened up the cable started it and it died right after i took it off choke....let it sit for 10 mins and not it wont start


Bummer man! Park the bike, get some beer cause USC is coming to kick Ohio ST all over the field.:busted:




 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.