rejetted main and now the pilot is wrong size?


6 replies to this topic
  • KGSloan

Posted March 12, 2011 - 04:41 PM

#1

hey guys,

i rejetted my bike today for the warmer months ahead and also because i put in the gytr silencer. Now I cannot get the bike to stall out by screwing the pilot jet in all the way where I could before.

the bike is a 2004 wr450f

I used to run it with no silencer in the stock can with stock pilot jet out two turns, 170 main jet, and jd blue needle 4th groove from the top. this seemed like an ok setup but it seemed rich as it would bog when the main circuit came on.

today i put in the 165 main jet and the jd red needle on the 5th groove from the top. still stock pilot jet. The bike runs good in the mid range but when trying to set the fuel screw i can't get it to stall out even when it's totally screwed in.

What change should i make next? it seems to run alright in the low rpms and low throttle settings...do i need to worry that i can't get the bike to stall out with the fuel screw?

thanks! I'm still a carb newb and am a little baffled here, don't wanna mess anything up

  • William1

Posted March 12, 2011 - 05:08 PM

#2

Main jet and pilot have no interaction, Air density is another matter.

Fuel Screw/Pilot Jet
Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method. Do it with the bike fully heated up.
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.

  • KGSloan

Posted March 14, 2011 - 07:25 AM

#3

well i checked the pilot according to the procedure above...

what's get's me is that I cannot kill the bike by turning the fuel screw all the way in. The bike starts VERY easily and runs good, so I don't much feel like changine the pilot jet. I mean, the bike starts real easy so should I bother messing with it?

currently my settings are as follows.

165 main
JD red needle on the 5th groove from the top
stock pilot
1 turn out on the fuel screw
small o-ring on the accelerator pump
opened air box
grey wire mod
gytr 96db performance insert in the stock can

I'm probably just going to leave it alone unless someone thinks I will do damage running it this way.

I always thought the pilot circuit operated the VERY low throttle settings, like below 1/8th throttle.

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  • KGSloan

Posted March 14, 2011 - 07:27 AM

#4

perhaps i needed to lower the idle speed some to get it to stall out, that part of the procedure i may not have gotten correct?

when turning the screw in, does it lean the mixture out?

  • dgcars

Posted March 14, 2011 - 07:38 AM

#5

perhaps i needed to lower the idle speed some to get it to stall out, that part of the procedure i may not have gotten correct?

when turning the screw in, does it lean the mixture out?


Idle speed has to be lower than normal. If you still can't get the motor to stall with the screw all the way in, go to a smaller pilot. If you are happy the way it is, leave it. It will not do any harm. :thumbsup:

  • William1

Posted March 14, 2011 - 09:35 AM

#6

You want the idle speed as slow as it can be then... you adjust the fuel screw to make it run as fast as possible. Then slow the idle speed down and revisit the fuel screw, try to make the bike as fast as possible. Keep doing this until the fuel screw makes the bike as fast as possible at the lowest idle speed. THEN... carefully close the fuel screw, paying attention to exactly how much you have to turn it. The bike should stall. Assuming it does, return the fuel screw to the best setting, start the bike, raise the idle to an appropriate speed.

Edited by William1, March 14, 2011 - 01:16 PM.
fix 8,000 typos


  • KGSloan

Posted March 14, 2011 - 12:29 PM

#7

You want the idle speed as slow as it can be then... you adjust the fuel screw to make it run as fast as possible. Then slow the idle speed down and revisit the fuel screw, try to make the bike as fast as possible. Keep doing this until the fuel screw makes the bike as fast as possible at the lowest idle speed. THEN... carefully close the fuel screw, paying attention to exactly how much you have to turn it. The bike should stall. Assuming it does, return the fuel screw to the best setting, start the bike, raise the idle to an appropriate speed.


thanks guys, i'll play with it some more and report back. always very helpful on this site :thumbsup:




 
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