Smoother Idle desired for WR450 ‘06


10 replies to this topic
  • thedktor

Posted March 10, 2009 - 07:17 AM

#1

.
Bought this bike new last year (old stock), it’s a UK model so unrestricted. Fitted a 94dB Scorpion pipe, which is not excessively loud but breathes much better than the stock one.

Jets are the usual 45 pilot, stock adjustable needle, 165 main etc, no bogging evident, and goes like a rocket!

Now, my issue is the idle is not as smooth as other bikes I’ve had and I feel it could be improved, but not really sure how.

I can adjust the pilot screw almost all the way in before the engine objects, and then turn it out several turns with not really a lot of difference. At idle it runs unevenly and the exhaust “misses” every second or two.

Any clues, or is it just a function of the relatively high tune/cams??

Thanks

Steve

  • thedktor

Posted March 10, 2009 - 10:40 PM

#2

Any help or ideas ?

  • William1

Posted March 11, 2009 - 02:21 AM

#3

Sounds like the pilot jet may be too large and the idle speed too low.

  • thedktor

Posted March 14, 2009 - 10:00 PM

#4

Good news. I made an adjustable screw by drilling the end and soldering in a small screw, bent at 90deg.

Lesson learnt – its essential to be able to adjust the thing accurately.

I found that I was only going about 2 turns out max, set to 3 turns out the bike was much better! Bike feels way smoother at low revs and is lovely and smooth on-off throttle, more like my old KTM-525, very pleasing.

I think based on this I should try a #48 …..

Steve

  • NMNORGE

Posted March 15, 2009 - 03:36 PM

#5

Good news. I made an adjustable screw by drilling the end and soldering in a small screw, bent at 90deg.

Lesson learnt – its essential to be able to adjust the thing accurately.

I found that I was only going about 2 turns out max, set to 3 turns out the bike was much better! Bike feels way smoother at low revs and is lovely and smooth on-off throttle, more like my old KTM-525, very pleasing.

I think based on this I should try a #48 …..

Steve


Yes, you should go up to a 48 pilot. Any adjustments outside 1/2 to 2 1/2 turns usually means pilot jet change.:)

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  • thedktor

Posted June 08, 2009 - 10:10 PM

#6

TRANSFORMED!!!

I fitted a #50 pilot I found in a box of bits and the bike is dramatically improved, running much smoother and more controllable at low revs. The #50 is perhaps a bit rich so I ordered up a #48 and have tried that now. Maybe the #50 is actually better, need to do some more trials.

The idle is still not as smooth as say a DRZ, but while moving the bike is just so much nicer with an easy to use pull off idle before launching into the WR’s familiar punch at say 3-4000rpm.

Steve

  • William1

Posted June 09, 2009 - 02:40 AM

#7

Fuel screw and pilot is for idle only and adjusted accordingly. Do not size them for off idle running issues.

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.
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.

  • thedktor

Posted June 09, 2009 - 09:06 PM

#8

Thanks for the reply William1 - good info.

The WR450 is not a smooth idlin' bike at the best of times, but the "Turn the screw in until the idle becomes rough or the bike stalls" technique does seem to work well to help determine pilot jet size so will continue to experiment!

Steve

  • thedktor

Posted June 09, 2009 - 09:43 PM

#9

OK, I'm spanning two threads really but here goes:

William1 said “Fuel screw and pilot is for idle only and adjusted accordingly. Do not size them for off idle running issues.”

I have learnt a lot over the last few weeks playing with the jetting on both the WR and my DRZ, and I think your point has hit home!

It would appear the “problem” I have been trying to fix is not actually in the pilot circuit, but due to the overlap between jet circuits, the pilot still affects the throttle opening position of concern, and can be used to cover up the actual issue!

This is why the #50 felt both too rich at idle, but better at partial throttle.

So, I borrowed the needle from my DRZ, which has an “N” straight portion, significantly richer than stock WR's "S".

Jump on the bike, and wow, talk about a “eureka” moment!

Where the bike would mildly lurch and snatch while trying to maintain a steady speed, no load, just above idle in 1st and 2nd , the bike now totally smooth and steady – amazing!

I was so dumfounded by this that I put the original needle back in, and went back out immediately just to check. Yup, the same problem back again, something I have lived with for the last year thinking it was just normal behaviour for this engine.

Worth pointing out that if you are an on-off throttle kind-a guy you may never even notice this issue. But those that have the need to maintain a steady speed, say for rocks, might want to take note.

Now, I am still wondering about what needle to use, but the DRZ needle #EMN seemed to work perfectly at all throttle openings……..

Steve

  • SXP

Posted June 10, 2009 - 06:38 AM

#10

Just for comparison, could you post the full name of the WR needle and clip position, and do the same for DRZ needle? Thanks.

  • thedktor

Posted June 14, 2009 - 11:21 PM

#11

Just for comparison, could you post the full name of the WR needle and clip position, and do the same for DRZ needle? Thanks.


Sent a PM and see this thread for more info:

http://www.thumperta...3639&highlight=

Steve




 
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