Missing/chugging Wr450f

[thetroy72]

I recently bought my wr450f and I love it although I need some advice it has started to miss in the 1/4 to 1/2 throttle when just cruising along. If I give it full throttle it seems to be fine as you get higher up in the throttle position. The bike starts fine and idles okay but just won't cruise nicely. Can anybody give me some suggestions, I tried a new plug, leaning the mix with a clip move up the needle but that made it worse. The jets are all stock factory settings as far as I am aware. Need some good advicel on this problem anybody got any ideas. The bike is a 2004 I live in Australia so the temp and humidity may be a little different to Europe etc.

[poffer]

Thats how this bike is.... Have exactly the same "problem" And if you look a little bit around in this forum you will find that a lot of people is asking question about this issue. If you disconnect the TPS (throttle possision sensor) I'l think your "problem" will be gone!

[SpeedBlitz]

This is a recent thread that has some good info regarding the TPS:

https://www.thumpertalk.com/forum/showthread.php?t=295205&parentpage=2

Also, you can read this one which is good IMO:

https://www.thumpertalk.com/forum/showthread.php?t=159518&highlight=stutter

If you want to find more info, search for "stutter" "hesitation" "surging" "TPS" "ACV" and you will find a lot of threads on the topic.

[Dan_Lorenze]

The TPS is not your problem... It's all jetting my friend.. When you say "Stock" jetting what is stock jetting in your bike? Chances are your bike is way too lean... Time to fatten it up.. You should spend some time and look in the jetting database for specs on jets that we're all using.. Your pilot should be around a 48 and your main should be around a 168 or 170 depending of elevation and temp... It's quite easy and fun to jet your bike but you've got to get into your carb and tell us what you have in there.. I'll help you.. But "Help me help you"

Dan

[poffer]

The TPS is not your problem... It's all jetting my friend.. When you say "Stock" jetting what is stock jetting in your bike? Chances are your bike is way too lean... Time to fatten it up.. You should spend some time and look in the jetting database for specs on jets that we're all using.. Your pilot should be around a 48 and your main should be around a 168 or 170 depending of elevation and temp... It's quite easy and fun to jet your bike but you've got to get into your carb and tell us what you have in there.. I'll help you.. But "Help me help you"

Dan

How can you say that the TPS isnt the problem? I have done everything with my carburator but the problem is still there! When I disconnect the TPS problem is gone! Have talked to a lot of guys who tells me that my bike is jetted/adjusted to rich. I'v tryed leaning it out on main jet/needle but this does not solve the problem. When I so tell this to these experts they then tell me that its probebly to lean.....!! The TPS has nothing to do with fuel/air mixture.

Can you tell me why I dont have the problems with tps disconnected???

pilot is 48, main is 170, elevation: from sea level and up to 600ft in tempratures between 40-70 farenheit

[extex]

I am no expert but I'll give you my experience with that exact problem of surging/missing. I read all the posts and disconnected the TPS. The surging was gone but I definitely noticed a less crisp throttle response. I reconnected it and tweaked my needle and the jets. I wish I had written down what I am running now but I would have to go through my tool box and look at all the jets I'm not using. I also moved the accelerator pump screw in a quarter turn and then out a quarter turn. The combination of what I have now eliminated the surge and provides as crisp, bog free response as I have ever had. So my opinion is that you can eliminate the surge without disconnecting the TPS.

[SJMC_DON]

It is the TPS. Well sort of, it's actually your ignition controller adjusting the timing based on the analog input it is getting from the TPS and various other sensors on the bike. It's normal, yes it will go away if you unplug the TPS but you will suffer in other situations when the timing needs to be changed for optimum performance. If you are only experiencing it while cruising and the bike performs fine otherwise I suggest you just learn to live with it. The rest of have

[vorra65]

The TPS is not your problem... It's all jetting my friend.. When you say "Stock" jetting what is stock jetting in your bike? Chances are your bike is way too lean... Time to fatten it up.. You should spend some time and look in the jetting database for specs on jets that we're all using.. Your pilot should be around a 48 and your main should be around a 168 or 170 depending of elevation and temp... It's quite easy and fun to jet your bike but you've got to get into your carb and tell us what you have in there.. I'll help you.. But "Help me help you"

Dan

Dan, I don't want to hijack anybody here-but. I'm in Sacramento, 04 WR and tweaking the carb. I'm getting closer, but I still have the wandering syndrome.GYTR exh. insert, YZ needle 4th clip, 168 MJ, 48 PJ, Zip Ty at 1.75 and just did the 40 LJ tonite. Like I said, it's real close but still feels like my wrist and the bike are "disconnected" down low, or whenever I'm not in it-sorta like it's hunting for a happy spot. I wish I had a better term to explain what I feel. Anyway, just for shit's and grins-I unplugged the TPS tonite after the new LJ test ride. Went for another ride "unplugged"-OK this is the way it's suppose to feel.

Can you give me lead, as to where to zero in now? I don't really want to leave the TPS unplugged, if I can cure it by massaging the fuel delivery.

Any help, is greatly appreciated. Thanks

[thetroy72]

Hi thanks for the replies seems to be hotly contested problem with quite a few options for a fix. Personally I would like to keep the tps connected so I am going to work on the jetting. I will pull the carby down again and have a look at the specs for the jets and post them soon thanks again for your help.

[Matty05]

Don't muck around with the TPS, GET YOUR JETTING RIGHT!!!

[poffer]

Don't muck around with the TPS, GET YOUR JETTING RIGHT!!!

VERY easy to say.. But it seems that nobody can tell me why the problems are gone when tps diconnected

Just have to mention: I'v also adjusted the tps out of specs both ways!! but the problem was on the same rpm as before. You can say that it is jetting but I have tryed everything without luck. I have had it both rich and lean on mid reg but the problem was exactly the same. I'm beginning to think if it could be a softwarebug in cdi unit.....

[Matty05]

If it is happening at the same rpms, it might be the sonics of your exhaust system.

To get the most out of a new exhaust system, a different cdi map to suit should be used.

I guess this is why vortex ignitions are popular as you can pick which map you like.

[Dan_Lorenze]

Guys, to the best of my knowledge the TPS is connected to the digital ignition system and varies ignition timing according to throttle position and engine rpm so that the ignition compensates for differing engine loads. The result is crisp throttle response and better fuel efficiency. Disconnecting the TPS (in my opinion) is a Band-aid for the problem.. I believe you will give up throttle control throughout the rpm range and maybe some loss of mpg. I'm certainly no expert in fuel systems nor do I claim to be but this is my understanding.

TheTroy72, From what I understand you have a "Stock jetted" euro WR, no grey wire and no throttle stop (that's stock). I can only assume (you know what happeneds when we assume) your bike is lean right from the factory. I can assume this because 9 times out of 10 these bikes don't come out of the crate properly jetted for anyone and any elevation or temp. These bikes are almost always too lean for most of us, also, for some reason each bike is different too..... You don't know what jets are in there so I can't really help you, I have to know exactly what's in your carb to help you with changes... The jetting database has more info in there than anything I've seen on Thumpertalk to date.. It's real impressive... Please take some time and take you carburetor off your bike, set in on your bench and lets get to work...

Dan

[poffer]

If it is happening at the same rpms, it might be the sonics of your exhaust system.

To get the most out of a new exhaust system, a different cdi map to suit should be used.

I guess this is why vortex ignitions are popular as you can pick which map you like.

Exhaust isnt the reason. Have exactly the same problem with stock exhaust.....

[Dan_Lorenze]

Dan, I don't want to hijack anybody here-but. I'm in Sacramento, 04 WR and tweaking the carb. I'm getting closer, but I still have the wandering syndrome.GYTR exh. insert, YZ needle 4th clip, 168 MJ, 48 PJ, Zip Ty at 1.75 and just did the 40 LJ tonite. Like I said, it's real close but still feels like my wrist and the bike are "disconnected" down low, or whenever I'm not in it-sorta like it's hunting for a happy spot. I wish I had a better term to explain what I feel. Anyway, just for shit's and grins-I unplugged the TPS tonite after the new LJ test ride. Went for another ride "unplugged"-OK this is the way it's suppose to feel.

Can you give me lead, as to where to zero in now? I don't really want to leave the TPS unplugged, if I can cure it by massaging the fuel delivery.

Any help, is greatly appreciated. Thanks

Vorra, first of all..... That's one slammin' Avatar...

Your bike is pretty much the same as mine, I can honestly say that I have zero bog anywhere. Here are my specs copied from the jetting database:

Model: 2005 WR450f US model

Cam Timing: WR (stock)

Main Jet: 170

Pilot Jet: 48

Fuel screw: MSR Hard Parts - 2 out (about)

Needle model/Clip position: 04 WR 4th pos

Starter Jet: 70

Leak Jet: 40 (50 is stock)

Accelerator pump cover: Factory R&D "Lightning"

Airbox lid (on or off): snorkel removed

AIS: Mark Lowe's Smog removal kit

Pipe: Yamaha GYT-R Aluminum slip-on Quiet cap

Air filter: UNI-This filter is a work of art!

Altitude where you ride: Sea level to 4000

Temperature where you ride: Varies, mostly 70s-80s

Degree of Jetting satisfaction: 10

I think your bike is set up perfectly, the only thing that might help out is the fuel screw.. I do have a Accelerator pump cover on my bike though I don't think it's solely responsible for my bog free ride. Is your Grey wire cut? Instead of cutting mine I pulled the pin out of the connector and folded it back onto itself.

As much as I don't like to mess with the factory settings on the Accelerator pump squirt duration I'll bet this might have something to do with some bikes.. Too much of a squirt of fuel going into the carb sometimes bogs the delivery down just enough to cause the hesitation some of us have..

[SpeedBlitz]

I'm surprised no one mentioned the ACV yet. Earlier this year when I was struggling with this problem, I searched a lot on the WR forum and the jetting forum and found a number of threads on the topic and there was a lot of debate regarding the surging/stuttering at constant throttle being either:

1-Poor jetting

2-ACV

3-TPS

4-Or a combination of the above.

I attacked all three and disabled the ACV, unplugged the TPS and changed my jetting and no more problems (though I can't point at a single root cause because I did all three at the same time); however as many suggested, TPS might just be a band aid, so I intend to re-connect it and see if my bike will remain stutter free with TPS connected (obviously, if it stutters, I will try to work on my jetting extensively to see if I can get rid). From what I read, it seems like many claimed they could get rid of the problem with good jetting (and ACV if necessary).

[poffer]

Have tryed disable the ACV but it had no affect on my problem..... Same shit whatever I'v tryed!

[vorra65]

Vorra, first of all..... That's one slammin' Avatar...

Your bike is pretty much the same as mine, I can honestly say that I have zero bog anywhere. Here are my specs copied from the jetting database:

Model: 2005 WR450f US model

Cam Timing: WR (stock)

Main Jet: 170

Pilot Jet: 48

Fuel screw: MSR Hard Parts - 2 out (about)

Needle model/Clip position: 04 WR 4th pos

Starter Jet: 70

Leak Jet: 40 (50 is stock)

Accelerator pump cover: Factory R&D "Lightning"

Airbox lid (on or off): snorkel removed

AIS: Mark Lowe's Smog removal kit

Pipe: Yamaha GYT-R Aluminum slip-on Quiet cap

Air filter: UNI-This filter is a work of art!

Altitude where you ride: Sea level to 4000

Temperature where you ride: Varies, mostly 70s-80s

Degree of Jetting satisfaction: 10

I think your bike is set up perfectly, the only thing that might help out is the fuel screw.. I do have a Accelerator pump cover on my bike though I don't think it's solely responsible for my bog free ride. Is your Grey wire cut? Instead of cutting mine I pulled the pin out of the connector and folded it back onto itself.

As much as I don't like to mess with the factory settings on the Accelerator pump squirt duration I'll bet this might have something to do with some bikes.. Too much of a squirt of fuel going into the carb sometimes bogs the delivery down just enough to cause the hesitation some of us have..

Yeah, me likey the avatar too! ? That's a p/shopped image from a full size photo of her in a pair of black A-Stars.

Thanks for the info.

Like I said, I'm real close and the ride with the TPS unplugged is what I want-but I'm unwilling to settle for a "band aid". Before I bought this bike I had the YFZ450 and throttle response was spot on. That thing would jerk the bars outta your hands, it pulled so hard.

What is the Factory R&D Lightning cover?

Tell me about your bike before and after the grey wire mod-

The off idle stumble, I almost feel it's the opposite of what some ideas feel. It almost feels like it's a rich condition, instead of lean. Like when you crack it, it's getting too much fuel. Anyway, I'm not giving up-till it's right.?

[Matty05]

Have tryed disable the ACV but it had no affect on my problem..... Same shit whatever I'v tryed!

The ACV justs cuts off the air when you back off completely to stop lean

condition or backfiring. This won't be your problem.

If you sincerely believe you have your jetting nailed, you can always gear your

bike around it.

[Dan_Lorenze]

Yeah, me likey the avatar too! That's a p/shopped image from a full size photo of her in a pair of black A-Stars.

Thanks for the info.

Like I said, I'm real close and the ride with the TPS unplugged is what I want-but I'm unwilling to settle for a "band aid". Before I bought this bike I had the YFZ450 and throttle response was spot on. That thing would jerk the bars outta your hands, it pulled so hard.

What is the Factory R&D Lightning cover?

Tell me about your bike before and after the grey wire mod-

The off idle stumble, I almost feel it's the opposite of what some ideas feel. It almost feels like it's a rich condition, instead of lean. Like when you crack it, it's getting too much fuel. Anyway, I'm not giving up-till it's right.?

The Factory R&D cover is an AP cover that adjust the squirt volume of the AP circit..

Grey wire, the dealer pulled it out of the connector before I picked the bike up. This could be the ticket for you.... If you have not done this, this could be the culprit....