wr450 hard start when hot


10 replies to this topic
  • mikey454

Posted April 27, 2015 - 10:06 PM

#1

Hi i have an 03 wr450 with a big bore kit in it. It is really hard to start when hot. Usually 4 or more kicks when stalled and 3 or more when shut off. Jefting is 168 main,48 pilot,#5 jd red and 1.5 turns out on the mix screw. It was about 68 degrees out today. It starts fine when cold without the choke which makes me think the idle mix is a little rich but it runs fine on the trail. Should i play with the mix screw and set it a little better or is this normal for an older 4 stroke.

  • mikey454

Posted April 27, 2015 - 10:11 PM

#2

Also i checked the valves when i bought it last year and it only has 70km on it since.

  • Slow and Jerky

Posted April 28, 2015 - 03:50 AM

#3

Wouldn't hurt to lean the idle/air a little, I've had those pilot screws back themselves out over time. Also, when it's hot are are starting in neutral or in gear? Sometimes that extra little drag from the clutch can make them pretty hard to start.



  • RMK800

Posted April 28, 2015 - 03:58 AM

#4

WR aren't overly cold blooded when starting. When I see this problem, it means you have too much fuel. I would go back to a 45 pilot jet and set you fuel screw two turns out. I guarantee you this will help your problem.

Edited by RMK800, April 28, 2015 - 04:12 AM.


  • William1

Posted April 28, 2015 - 05:08 AM

#5

48 pilot is too large. A red flag is the no choke needed on cold start.

 

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 fuel 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 knob 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 speed (knob) 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 fuel 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 1,850 rpm, but go by the spec in your manual.
 



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  • ThumpMe

Posted April 28, 2015 - 05:22 AM

#6

+1 on the above post about bike being in neutral for easier starts!

 

I have TWO that are both pretty hard to start when killed or they die. Have been working on one for years, even did a write up last year where I tore into the clutch about 12-13 times over the course of several months. Got the drag reduced big time, and the clutch works like a dream now, but it STILL does not like to light back up when stalled or killed when in gear. 

 

 I have tried re-jetting and believe I will do that some more but this time will concentrate more on the start jet more. I think they refer to it in parts list as the slow jet? Problem is I believe  they only have four options. I can change that though! 

 

 This newer one I have (an '07) is real similar. Crank and crank if in gear to re-light. And sometimes twisting the throttle a couple times and it will re-light, but usually have to go to neutral to allow it to spin good enough to re-fire.

 

 Really sucks (having to go back to neutral)  when you flame out on a steep or knarly section.


Edited by ThumpMe, April 28, 2015 - 05:25 AM.


  • mikey454

Posted April 28, 2015 - 07:16 AM

#7

Thanks i will try going down to a 45 pilot and setting it proper tonight. Another quick qustion about it. If i dont roll it over to tdc its like hitting a wallhalf way through the stroke. The last time i had it out and didnt quite kick it right the kick starter skipped a couple of times. I stalled it alot after that and kicked it allot and it dint happen again but now its bugging me lol. Should i pull the side off and check the ratchet? And is there a decompression valve that i can adjust or is it par for having a big bore with high compression?
Thanks i will try going down to a 45 pilot and setting it proper tonight. Another quick qustion about it. If i dont roll it over to tdc its like hitting a wallhalf way through the stroke. The last time i had it out and didnt quite kick it right the kick starter skipped a couple of times. I stalled it alot after that and kicked it allot and it dint happen again but now its bugging me lol. Should i pull the side off and check the ratchet? And is there a decompression valve that i can adjust or is it par for having a big bore with high compression?

  • RMK800

Posted April 28, 2015 - 01:10 PM

#8

William makes a good point. All bikes should always require a choke when first starting. Doesn't matter if it's 30 degrees or 90.

  • DonnieD

Posted April 28, 2015 - 01:57 PM

#9

William makes a good point. All bikes should always require a choke when first starting. Doesn't matter if it's 30 degrees or 90.

My WR is jetted and same thing, requires choke when cold.

 

But my street bike (also jetted) does not require choke on a cold start unless it's really "cold" outside. It's much easier to crank cold or hot than the WR.

 

Just saying. 



  • toten

Posted April 29, 2015 - 08:26 AM

#10

William makes a good point. All bikes should always require a choke when first starting. Doesn't matter if it's 30 degrees or 90.

I'm not so sure about that, if it's 90 I wouldn't expect to need choke (especially if the bike is sitting in the sun). 



  • RMK800

Posted April 29, 2015 - 04:09 PM

#11

I'm not so sure about that, if it's 90 I wouldn't expect to need choke (especially if the bike is sitting in the sun).

I can start my bikes without the choke, however, it's always harder. I can turn the choke on and flip the throttle twice and it will start within one or two kicks without touching the throttle again. I have five bikes that I can do this on. I always kickstart when first starting and their all electric start. After warm up, I than use the button.

Edited by RMK800, April 29, 2015 - 04:10 PM.





 
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