Engine dying from off-idle throttle snap... '06 WR450 JD Kit Installed

[grappler]

Let me preface this thread by saying I am BRAND NEW to this whole carb jetting game and I'm trying to get my small brain around it.

Ever since I purchased my '06 WR450, the engine stalls if I'm at idle and snap on the throttle. I'm at ~3000 ft. altitude and yesterday I installed my newly arrived JD jetting kit per the instructions for my altitude and high heat ranges. If I'm above idle or anywhere else in the throttle range, response is crisp and clean. I couldn't be happier. It does annoy me however that I'm not able to resolve this off idle problem. I've done some searches here and combed through the mountains of jetting info but maybe I'm just not getting it. Any suggestions? Besides switching the main jet to a 165 per and using the recommended JD needle and settings, my carb is completely stock.

Any help is much appreciated!

Grappler

[642MX]

Have you installed a longer fuel screw so you can adjust the pilot circuit while the engines is running?

[grappler]

Yes, sorry, forgot to mention that I have installed a Zip Ty fuel screw and I removed the AIS.

[642MX]

Which JD needle are you using?

[grappler]

Red needle with clip in 5th from top position as per the instructions.

[642MX]

I would try turning the fuel screw until the bog goes away. 0-1 turns out you need a smaller pilot jet, 3+ turns out and you need a larger pilot jet. If playing with the fuel screw doesn't help then you may want to remove the carb and give it a good cleaning.

[grappler]

Thanks, 642. Is there any specific procedure to doing that. or do you just turn and try? Any need to let it idle for a set amount of time between changes or is it immediate?

[642MX]

Thanks, 642. Is there any specific procedure to doing that. or do you just turn and try? Any need to let it idle for a set amount of time between changes or is it immediate?

I typically start at one turn out and with the motor idling, then I slowly turn the screw out 1/4 turn at a time until I find the snappiest throttle response. It takes some time, but you should be able to feel and hear when its right. Its a bit of a trial and error process. Good luck.

[wedrivezs]

We've got the same problem, we'll give it a try.

[odonnks]

I've been working thru this also, I'm at around 1000'

Had it pretty much licked at 32 deg. Temp rose to 70 and it re appeared.

After the jetting changes and a freeer flowing stock pipe. (second internal baffel removed and PMB insert) Jetting ended up as follows.

Main at 168

Leak at 35 (I may bump this up a bit)

Pilot at 48

JD needle at red #5

One of the best things I did was adjust the 'slop' from the accel pump.

After it was worked out I also installed a Boysen quickshot. To me it made the throttle more 'sharp'

[grappler]

Thanks, all. I'll see if I can get some quality time with the WR this week and get this problem dialed out.

[Stiletto_72]

Get a smaller leak jet. I installed the JD kit and the bike ran great, except when the throttle was wicked. I had even installed the power surge kit, with the #65 recommended leak jet. I think too much fuel was passing back into the bowl with the 65 LJ. I installed a #40 leak jet, and wicked the throttle in my driveway and laid 8 foot patch of rubber. With the smaller LJ I can also blip the throttle all day and not the have the accelerator pump chamber go empty.

The only problem I have with the throttle range now is when i'm in 4th or 5th and roll the throttle wide open I get more of a bog, than strong acceleration. I'm thinking I need to try a smaller mainjet.

I also installed a toggle switch for the grey wire mod. I cut the grey wire near the connector and soldered a length of wire to the toggle switch. I mounted the toggle switch to the frame where the AIS component was. I just a 5/8" wide strip of 3/16th inch alunimum as a mounting bracket. It's nice since the WR timing is nice for the trails and the wilder yz timing for hill climbing and tearing it up.

G

[old man dan]

I would try a 48 pilot and make sure your idle isn't set too low. Set the idle at 1900 and adjust your fuel screw starting at 1 turn out and find the sweet spot.

[YamahaWR450FMike]

if I stab my throttle wide open from idle it will kill the engine on my WR450F even have the JD jetting.

[odonnks]

Decrease your leak jet size and adjust the slop from your AP linkage.

The owners manual has the AP linkage instructions, takes 10 min tops.

[OneToGo]

I've been working thru this also, I'm at around 1000'

Had it pretty much licked at 32 deg. Temp rose to 70 and it re appeared.

After the jetting changes and a freeer flowing stock pipe. (second internal baffel removed and PMB insert) Jetting ended up as follows.

Main at 168

Leak at 35 (I may bump this up a bit)

Pilot at 48

JD needle at red #5

One of the best things I did was adjust the 'slop' from the accel pump.

After it was worked out I also installed a Boysen quickshot. To me it made the throttle more 'sharp'

You have the same jetting as mine except I have #40 leak, fuel screw 1.5 out - I dont have the Boyesen...

And now, around 1/8 to 1/4 throttle transition on the way up I get a stutter - fuel screw little affect, slightly better at 1.5 out.

(Temps are on the rise here in a big way now....80+f and around 90% humidity today - so, I suspect a Rich condition in that throttle range.)

The reason I post here and not in jetting is to ask if you have tried the JD Red in clip #4 position without changing anything else??

Also, do you have your ACV blocked in any way?

Cheers

[Matty05]

You have the same jetting as mine except I have #40 leak, fuel screw 1.5 out - I dont have the Boyesen...

And now, around 1/8 to 1/4 throttle transition on the way up I get a stutter - fuel screw little affect, slightly better at 1.5 out.

(Temps are on the rise here in a big way now....80+f and around 90% humidity today - so, I suspect a Rich condition in that throttle range.)

The reason I post here and not in jetting is to ask if you have tried the JD Red in clip #4 position without changing anything else??

Also, do you have your ACV blocked in any way?

Cheers

yes, you are rich in that 1/8 - 1/4 range.

You might just have to shim the needle a bit with tiny washer for half clip adjustment. Either that or go to 4th clip JD red. I am at 4th clip JD red, I live in top of Australia, so very similar climate to you.

His ACV not blocked in, not with a 48 pilot jet!

[Matty05]

I would try a 48 pilot and make sure your idle isn't set too low. Set the idle at 1900 and adjust your fuel screw starting at 1 turn out and find the sweet spot.

Grappler - you need to do this!

BTW, 1900rpms is just a high idle. This is to be sure the pilot circuit is functioning properly with sufficient airflow for constant fuel flow.

Set the screw to the mark where you hear the engine change to max RPMs at this high idle. Turn it back off the mark a few times to make sure you have set it correctly.

[Matty05]

if I stab my throttle wide open from idle it will kill the engine on my WR450F even have the JD jetting.

It shouldn't do this? What pipe you got?

[Matty05]

The only problem I have with the throttle range now is when i'm in 4th or 5th and roll the throttle wide open I get more of a bog, than strong acceleration. I'm thinking I need to try a smaller mainjet.

Wrong way. Go bigger on the main jet.

Bog is lean, studddddder is rich.