NEWBIE, of sorts, with TPS & Rad???'s

I've been riding for years and lurking these forums for just as long. I finally decided that being both older and 'old school' was starting to take its toll. I finally sold off my last dirt ride (a '91 XR600, Al Baker Edition) and jumped into a new '08 WR450F. I did my research before doing the deal, but it looks like there's no escaping the common issues.........:D

TPS: Yep, even on the '08 the 1/4-3/4 throttle stutter is still a problem. Did the usual AIS elimination, grey wire, FMF pipe, dyno-jetting 3 times, etc.... Still does it!:ride:

Did the searching and the choices seem to be MORE jetting experiments or possibly after-market ignition. I ride at elevations from 5000-14,000ft. Can anyone document the common resolve?

Radiator Guards: Seems to be lots of thoughts on this one, but I really want a bullet-proof version that won't restrict airflow and will actually take a REAL hit and survive.:banghead: I don't care if it takes me 2-days to install, provided it will work! Any recommendations/experiences on the 'high-end' versions for an '08 would be appreciated!:)

Thanks in advance!:worthy:

Regarding the stutter, a James Dean jetting kit along with a Maerge Racing extended fuel screw helps a lot. That said, it has been documented teh Wr's have a stutter issue, mostly at very low rev's that is CDI related. Not a lot you can do about it other than a aftermarket CDI like the vortex. I have all but elminated the stutter on my WR by careful jetting. Do a search, there is a thread that James Dean and (I think) SMCDon did on this.

For radiator guards, get Unabikers, by far the best. You may also want to consifer a Flatlands skid plate, also probably the best skidplate.

Thank you for your input, William1!

Getting the jetting set for the range of altitudes I ride seems to negate the 'perfect' jetting to solve the stutter. I guess I'll start heading for the JD and Vortec kits.:)

I have several other Yami toys and you would think they would have addressed this issue with the WR by now.

The Unabikers seemed to get just as many negatives as positives when I did a guard search, but I was hoping there were alternatives other than that and the Moose, Utah, etc (that are all the same thing).........

I already have the new Works skid plate. It came out to be a little cheaper than the Whipps and is very similar and does it's job (so far).

Get the JD jet kit, hold off on the Vortex. Install the jet kit per JD rec's. Tweak it if need be to get it the best possible. If you have bog issues, then address them. You may find the stutter is nearly imperceptable. Mine is.

Also, keep in mind any bike properly jetted for a particular altutude will run worse when the altitude changes, ie, more than 2,000'.

The down side to the Unabikers is it is a pain to install them and some maintenance on the bike is more difficult accordingly. But this is the trade off you have to have to get the strength. Try to look about and see how the other brands are made and compare. A lot of the guards being made are just sheet alloy, strong to a point and then folds up. The Unabikers use a fairly thick series of bars across the front and back in addition to sheet alloy.

The poster thread about the stutter is SJMC_DON

Before you run off and buy the Vortex CDI (which might be fun to have). Try and set the TPS to the upper range voltage value at closed throttle. This will help minimize the stutter and will make your attempt to fix the problem with jetting more successful.

Check your manual on the older bikes the voltage range is .58V to .78V with the circut connected and checked via back probing the connector . You should then adjust the TPS after you have adjusted your carb for proper idle. Adjust the TPS by moving the TPS to acheive close to .75Volts closed throttle. The manual describes the procedure pretty well.

This may not make the stutter go away completlly but it should bring it down to an acceptable level that you can deal with.:)

GCannon, that's the kind of info I'm looking for! The bike is going back on the dyno next week to lean it out some, so we can play with your suggestion at the same time. I did the checks per the manual and it reads right (per factory spec.) but we'll try dialing it in more.



hey there,

following your thread.. my 08 has a studder still..

bought the JD jetting kit... but been holding off.. cuz most of my riding is @ 780 feet

as far as the unibiker fit and finish great. seemed really strong.

when i fell over @ about 2.5 mph (not joking.) wimpy tip over. bent the rad and guard. the guard is angle'd to cut into the dirt till something has to give. if they angle'd

it the other way... it would be way way way better.

i truly believe if i didn't have the guards on, i would have sustained no damage!! not impressed. thats for sure!



That's what I've been hearing Warts. I may have to come up with my own version that's a brace first, shield second.

William1 has me confused with someone else (I hope it's a real smart guy:busted:) ... I have chimed in on TPS threads before but my advice has always been to unplug it if it's that much of a nuisance, (I am not aware of the side effects in doing so but maybe someone here can enlighten me. I have heard reports of a noticeable drop in power but nothing confirmed on a dyno nor by the seat of my pants)... do you dual sport the bike or ride a lot of two track? I have never noticed this stutter on any thing but smoothe firma at a steady cruising RPM so I have since re-connected mine because I figure it must do something to improve the power delivery while offroad riding.

In regard to the rad guards... I would never suggest anything but Unabikers. I have tried them all and have spent more $ than I want to even think about on new radiators and repairs.... my 07' with the Unabikers has 2 seasons of racing and hard riding on it, I have hit trees, walls, other racers, concrete, you name it and I still have the OEM rads with no repairs or anything more than a barely noticeable tweak and thats a hell of a lot more than I can say for past bikes with other guards i.e., devol, MSR, works connection and moose. The slow moving, or parked, tip overs are the worst on these bikes when it comes to rad damage.

Sorry 'bout that, SJMC_DON

I am often confused, my wife thinks it is one og my endearing traits. Of course, she is batty too.

Since I was mistaken, I took the liberty to locate the thread:

LOL, it was WR450SM 's thread! At least I remembered he had 'SM' in his name.....

I have the Force Rad Guards and they have taken a real beating and survived.


I like the looks of the Force Guards, but how's the cooling?!? I'm not convinced that the full-face guards are a good thing,,,,,yet, which brings up another point: electric fans. Anyone done that one yet?

SJMC_Don: I do mostly woods riding from 5000-14,000ft. Aside from jetting (for that range it's not possible), the stutter is a real issue and not just at a steady cruise. I've disconnected the TPS and did notice a lack of throttle response. I'm not sure if the CDI goes into a default timing mode with the TPS disconnected, but I can sure feel negative effects. Has anyone checked the timing curve/line with the TPS out of the loop?:)

Sorry 'bout that, SJMC_DON

I am often confused, my wife thinks it is one og my endearing traits. Of course, she is batty too.

Since I was mistaken, I took the liberty to locate the thread:

LOL, it was WR450SM 's thread! At least I remembered he had 'SM' in his name.....

That's the thread that proves the problem exists, but the resolve didn't seem to be real conclusive to me. A Vortec on map 7 may help, but I'm looking for the source of the original problem with what the bike has on it from Yami. I'm guessing that for emission reasons that the OEM timing map or CDI is all jacked up to work with the AIS.

Well, I think you are close on your diagnoisis. My suspicion is it is emissions related. Heavily retarded ignition advance.

I agree on your interpertation of the thread too. It answered some questions but still left speculation.

I have to say, on my WR, the problem is nearly completely gone, certainly enough that I have to look for it and even then, really cannot discern it. I did this by very careful jetting.

About your tps questions

I have an 06 wr supermoto which i commute and hooliganise on

Like your 08 i was desperate to get rid of my throttle stutter and

i had the bike professionally dyno tuned

tried different voltages on the tps (sidenote .072 made it slightly less harsh)

put in an iridium plug

and bought a vortex x10

all this did not fix the stutter however the stutter went away if i disconnected the TPS plug. I was not satisfied with this fix as the bike felt flat and raspy downlow and at fine throttle positions whilst cornering

i was of course slightly angered that my vortex did not fix the issue. but i do not blame the company as i love its other effects it has on the bike especially the new redline

after recently seeing james dean posting some information about his and a customers findings with the vortex while trying different maps on JD's dyno i tried his finding.

JD basically said every map on the vortex x10 EXCEPT map 7 included yamaha's factory stutter.

I did not believe this but i was willing to try as i really do respect JD

I reconnected my TPS changed my custom map to number 7 (yz450 map) and went for a ride. He was right map 7 does not contain the stutter we experience at steady throttle. However if i switched it to the vortex map1 (wr best power map) via the handle bar switch stutter came back as strong as ever.

Hope this helps :)

Thank's for the reply Nitro, but I did finally get the stutter fixed. It took the GYTR-AIS removal kit "mystery needle" set on the 2nd from the top and a 152 main jet. Runs VERY well now, and I don't start to get the stutter back until above 11,000ft!:)

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