WR450 Surge

Whats Up Guys

I have a quick question that i think you might be able to help me with. When I hold the throttle open at a constent spot my 05 WR450 seems to stutter and jump. Is this a jetting problem or could it be the TPS. Any help would be greatly appreciated.

Thank You

Unplug your TPS and test ride it. If it still does it try adjusting the needle. I got rid of my surge by installing a JD jet kit.

Install the GYTR AIS removal kit (if you haven't already)

I ride in Parker a lot and my bike (06') runs great - never had a problem for 2 years

Sounds like jetting to me. Maybe its running a little lean.

How is your carb setup? Do you have a pipe?

Sound like a classic case of TPS-idis :thumbsup:

+2 on the TPS/WR/CDI-itus

+2 on the TPS/WR/CDI-itus

The ignition is usually the source of Yamaha WR's stuttering at steady speed and light loads. I see it often on the dyno running at light loads. The ignition spark is monitored by the tach pickup and the air/fuel probe is measuring at the same time. The ignition (engine speed readout) will spike off every few seconds and come back while the wheel speed is steady and air/fuel looks good.

The graphs below are results from multiple runs placed together in each graph. All of these are low-throttle, low power output, just as you find with steady road riding.


See below-


The wheel speed is in the 30-45mph range and the throttle range is low throttle with low power output at the same time. The air/fuel mixture is in an acceptable range and isn't causing this type of result.


Many more runs on this graph, using both 4th and 5th gear.


Hey James, thanks for posting the pics of the "sparkin' wackyness".

Now the next question is, can a CDI from the same year Yamaha YZ resolve the problem (enough to justify the expense) for a WR?

We all pretty much run with the Grey wire disconnected already. Or does a bullet have to be bitten and a Vortex bought?

I am wondering the exact same thing, if i disconnect my tps i lose power, it's noticible, and i don't like it, so I need to know how to fix it also.

Ok maybe a stupid question. Mine is doing the same thing. What is the TPS?

Throttle Position Sensor

It 'reads' the throttle position and tells the CDI. To this it adds the engine rpm and determines the amount of spark advance.

Your owners manual has a pretty good section on it.

Throttle position sensor, located on the left hand side of the carb with a short pigtail and one connector on it. It tells the CDI how much throttle you are giving it so it can adjust the timing accordingly for more power.

**** I knew it.....

Does anybody have a solution?

Has anyone tried to actually see what this is caused by. I mean hooking a labscope up and seeing what signal is dropping out to cause this ignition problem(TPS, pickup coil, stator etc). Unplugging components and swapping parts seems so primitive(like a backyard mechanic). But unless you have the access to a dyno it would be hard to balace a scope and read it as you ride down the trail.

yeah, a guy here put it on a scope and posted a pic, change the cdi to aftermarket one will fix it.

My WRF has exactly the same problem. Done the grey wire/exhaust/open airbox/ jetting. When i grab the throttle hard there is absolutely no problem... when i cruise at steady speed but at high rpm it sputters instantly then stops and so on. No problem when i cruise at low rpm.

Soulds just like mine - low rpm is OK at steady throttle, but higher RPM sputters and misses every couple of seconds. I'm going to give JD jetting a call today to see what he thinks about fixing the problem.

Soulds just like mine - low rpm is OK at steady throttle, but higher RPM sputters and misses every couple of seconds. I'm going to give JD jetting a call today to see what he thinks about fixing the problem.

now that mine is jetted(TPS is still connected)... I can say that mines misses too. I only notice it when I'm tring to hold steady throttle. for example trying to do steady 25 mph on a park road with a speed limit. I don't notice it at all on the trail.

I'd like to try a new CDI, but the only one I know of is the Leovince fast box. and I'm not really interested in paying $400+ just to try it out.

Wondering if anyone has changed the TPS and found that the surging went away?

Its $180 replacement and would like to know if its going to fix the problem before I lay the ca$h out.

If I change the TPS. Are there adjustments to be made once it is on, or is it just plug and play??

Thanks Ian

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.

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