WR450 Surge

My 05 does this too, always has. The second I twist the throttle it's crisp and no stutter so it really hasn't bugged me too bad. However I was reading some other threads today about this and it was suggested to calibrate the TPS near the high end of the specified range. Mine was at the low end (.6v) so I set it at .73 but it's too cold and rainy/snowy to take it for a test ride. As soon as I do, I'll report back.

Summit you aren't kidding about the weather:rant: Are you running the JD jet kit?what are you running in your carb? I too have the surge and notice it when I'm riding the roads. It sucks but I don't notice it on the trail.

I'm running

Year: 2006

Model (400 - 426 - 450): WR450

Cam Timing (WR/YZ): WR

Main jet: 158

Pilot Jet: stock

Leak Jet: #60

Starter Jet: 65 (Stock)

Fuel screw (turns out): ZIP TY Fuel Screw 1.5 Turns Out (still tuning)

Needle Model/Clip position: JD Red / 3rd Position

Grey Wire Mod (Y/N): Y

TPS Connected (Y/N): Y

Airbox Snorkel/Lid (on or off): Off

AIS Removed (Y/N): Y

Airfilter Brand: No toil

Exhaust Brand: FMF Q4

Average Altitude: 5000_9000ft

Average Temperature: 70 - 85 F

Degree of Satisfaction (0-10): 9

Additional Mods/Comments: I have been running red #4 in cooler temps but it was still to rich. I just put in the #60 leak jet and have eliminated the initial throttle hesitation. I will probably changing the main jet depending on temp. I have done the o-ring mod too. If I don't find this set up working I will be pulling out the JD needles and go with stock from here on out. I also have a quickshot 2 on the carb.

Summit you aren't kidding about the weather Are you running the JD jet kit?what are you running in your carb?

No JD kit. I'm running 168 main, 48 pilot, GYTR needle on 4th groove.

My 2006 YZ450F also has TPSitis. I have been riding without the TPS connected for some time now and the bike still has plenty of power for my 170# frame.

If I read JD's repsonse correctly, he was saying that there was no loss in wheel speed or power despite the sputter?

I have an 03 WR450 and this stuttering problem has been bugging me for 10 years. I recently installed a Tinytach. I had to set it for multiple sparks per revolution to get it to read the correct rpm's. That tells me tht the ignition fires more than once. Now check this out. When the RPM's reach arround 3000 RPM and above, the reading on the Tinytach reads half the number. ie 1500 RPM.. I think that the CDI changes from 4 sparks to 2 per fire. Oddly enough, thats the RPM range that the stutter happens. I think the CDI is changing from 4 to 2 fires and if we are cruizing at that rpm its cutting in and out of two differnt modes resulting in the stutter.

 

03, WR450

yz timing

all mods

GYTR exhaust

JD Jetting

Gents, 

My '04 WR 450 exhibits the low speed, constant throttle surging/balking symptoms mentioned above. Also, it belches up a healthy backfire on closed throttle deceleration. Would this lean toward some previous 'wizard"s" jetting experiment? Or still sounds like ignition?

Gents, 

My '04 WR 450 exhibits the low speed, constant throttle surging/balking symptoms mentioned above. Also, it belches up a healthy backfire on closed throttle deceleration. Would this lean toward some previous 'wizard"s" jetting experiment? Or still sounds like ignition?

 

Until you bring your 11 year old carb back to factory tolerances you will never know exactly what it is.

The carb has wear parts and know failure points.

Deal with them first...but you probably just have dirt in your pilot jet, and your fuel screw has never been adjusted properly

 

Hot start

Emulsion tube

AIS (remove)

Slide plate seal

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